Zeitschriftenartikel zum Thema „Carbon-hetero bond“

Applications of in situ generated ferromagnetic α-Fe₂O₃ NPs as an efficient and recyclable catalyst for carbon–carbon bond formation via Sonogashira–Hagihara coupling reactions and the synthesis of pyran derivatives by hetero-Diels–Alder reactions have been demonstrated.

Vinylogous enolate and enolate-type carbanions, generated by deprotonation of α,β-unsaturated compounds and characterized by delocalization of the negative charge over two or more carbon atoms, are extensively used in organic synthesis, enabling functionalization and C–C bond formation at remote positions. Similarly, reactions with electrophiles at benzylic and heterobenzylic position are performed through generation of arylogous and heteroarylogous enolate-type nucleophiles. Although widely exploited in metal-catalysis and organocatalysis, it is only in recent years that the vinylogy and arylogy principles have been translated fruitfully in phase-transfer catalyzed processes. This review provides an overview of the methods developed to date, involving vinylogous and (hetero)arylogous carbon nucleophiles under phase-transfer catalytic conditions, highlighting main mechanistic aspects.

For a long time, the organic chemistry of sulfur dioxide (SO2) consisted of sulfinates that react with carbon electrophiles to generate sulfones. With alkenes and other unsaturated compounds, SO2 generates polymeric materials such as polysulfones. More recently, H-ene, sila-ene and hetero-Diels–Alder reactions of SO2 have been realized under conditions that avoid polymer formation. Sultines resulting from the hetero-Diels–Alder reactions of conjugated dienes and SO2 are formed more rapidly than the corresponding more stable sulfolenes resulting from the cheletropic additions. In the presence of a protic or Lewis acid catalyst, the sultines derived from 1-alkoxydienes are ionized into zwitterionic intermediates bearing 1-alkoxyallylic cation moieties which react with electro-rich alkenes such as enol silyl ethers and allylsilanes with high stereoselectivity. (C–C-bond formation through Umpolung induced by SO2). This produces silyl sulfinates that react with carbon electrophiles to give sulfones (one-pot four component asymmetric synthesis of sulfones), or with Cl2, generating the corresponding sulfonamides that can be reacted in situ with primary and secondary amines (one-pot four component asymmetric synthesis of sulfonamides). Alternatively, Pd-catalyzed desulfinylation generates enantiomerically pure polypropionate stereotriads in one-pot operations. The chirons so obtained are flanked by an ethyl ketone moiety on one side and by a prop-1-en-1-yl carboxylate group on the other. They are ready for two-directional chain elongations, realizing expeditious synthesis of long-chain polypropionates and polyketides. The stereotriads have also been converted into simpler polypropionates such as the cyclohexanone moiety of baconipyrone A and B, Kishi’s stereoheptad unit of rifamycin S, Nicolaou’s C1–C11-fragment and Koert’s C16–CI fragment of apoptolidin A. This has also permitted the first total synthesis of (-)-dolabriferol.

A proof-of-concept for synthetically challenging cyclic and acyclic perfluoroalkylation of (hetero)arenes driven by the valence change of a cobalt catalyst with X(CF₂)₄X is demonstrated.

The interest in functional materials possessing improved properties led to development of new methods of their synthesis, which allowed to obtain new molecular arrangements with carbon and heteroatom motifs. Two of the classical reactions of versatile use are the Friedel-Crafts and the Bradsher reactions, which in the new heteroatomic versions allow to replace ring carbon atoms by heteroatoms. In the present work, we review methods of synthesis of C–S and C–P bonds utilizing thia- and phospha-Friedel-Crafts-Bradsher cyclizations. Single examples of C–As and lack of C–Se bond formation, involving two of the closest neighbors of P and S in the periodic table, have also been noted. Applications of the obtained π-conjugated molecules, mainly as semiconducting materials, flame retardants, and resins hardeners, designed on the basis of five- and six-membered cyclic molecules containing ring phosphorus and sulfur atoms, are also included. This comprehensive review covers literature up to August 2020.

Multidimensional carbon isotopes, such as carbon nanotubes (CNTs) and graphene, have been extensively researched as intrinsic catalytic materials or hetero supports for catalytically active metal sites, owing to their high conductivity, thermal stability, and chemical inertness. However, the enhanced catalytic performance of most transition metal-based catalysts on carbon supports is considered to be primarily due to improved carrier transport kinetics resulting from the conductivity of carbon supports, although there may be other possible effects that are not yet well understood. In this presentation, we propose CNT-decorated Ni(HCO3)2 (denoted as Ni(HCO3)2@CNT) as a bifunctional catalyst for both the oxygen evolution reaction (OER) and the oxygen reduction reaction (ORR). The sp3-like carbon in CNTs can induce charge transfer to the Ni active site within Ni(HCO3)2, which in turn induces strain in the Ni-O bond. This strain-induced Ni active site can stabilize the *O intermediate, leading to significantly lower potential barriers for the potential-determining steps of both OER and ORR compared to pristine Ni(HCO3)2. The adjustable catalytic activity enabled by interfacial charge transfer and its contribution to local structural distortion presents a straightforward approach to designing low-cost, highly efficient, and multifunctional catalysts for sustainable chemical energy conversion.

The polymeric graphitic carbon nitride (g-C3N4) has been one of the interesting earth abundant elements. Though g-C3N4 finds application as a photocatalyst, its photocatalytic behaviour is limited because of low efficiency, mainly due to rapid charge recombination. To overcome this problem, several strategies have been developed including doping of metal/non-metal in the cavity of g-C3N4. Moreover, the CoFe2O4 NPs have been used in many organic transformations because of its high surface area and easy separation due to its magnetic nature. This review describes the role of cobalt ferrite as magnetic nanoparticles and metal-doped carbon nitride as efficient heterogeneous catalysts for new carbon-carbon and carbon-hetero atom bond formation followed by heterocyclization. Reactions which involved new catalysts for selective activation of readily available substrates has been reported herein. Since nanoparticles enhance the reactivity of catalyst due to higher catalytic area, they have been employed in various reactions such as addition reaction, C-H activation reaction, coupling reaction, cyclo-addition reaction, multi-component reaction, ring-opening reaction, oxidation reaction and reduction reactions etc. The driving force for choosing this topic is based-on huge number of good publications including different types of spinels/metal doped-/graphitic carbon nitride reported in the literature and due to interest of synthetic community in recent years. This review certainly will represent the present status in organic transformation and for exploring further their catalytic efficiency to new organic transformations involving C-H activation reaction through coupling, cyclo-addition, multi-component, ring-opening, oxidation and reduction reactions.

In this paper, an efficient synthetic route from pyrazole-chalcones to novel 6-aryl-5-hydroxy-2-phenylpyrano[2,3-c]pyrazol-4(2H)-ones as 3-hydroxyflavone analogues is described. The methylation of 5-hydroxy-2,6-phenylpyrano[2,3-c]pyrazol-4(2H)-one with methyl iodide in the presence of a base yielded a compound containing a 5-methoxy group, while the analogous reaction of 5-hydroxy-2-phenyl-6-(pyridin-4-yl)pyrano[2,3-c]pyrazol-4(2H)-one led to the zwitterionic 6-(N-methylpyridinium)pyrano[2,3-c]pyrazol derivative. The treatment of 5-hydroxy-2,6-phenylpyrano[2,3-c]pyrazol-4(2H)-one with triflic anhydride afforded a 5-trifloylsubstituted compound, which was further used in carbon–carbon bond forming Pd-catalyzed coupling reactions to yield 5-(hetero)aryl- and 5-carbo-functionalized pyrano[2,3-c]pyrazoles. The excited-state intramolecular proton transfer (ESIPT) reaction of 5-hydroxypyrano[2,3-c]pyrazoles from the 5-hydroxy moiety to the carbonyl group in polar protic, polar aprotic, and nonpolar solvents was observed, resulting in well-resolved two-band fluorescence. The structures of the novel heterocyclic compounds were confirmed by 1H-, 13C-, 15N-, and 19F-NMR spectroscopy, HRMS, and single-crystal X-ray diffraction data.

Abstract DFT calculations were done for the (hydroperoxo)metal complexes with η1-coordination mode, where metal ions are Fe(III), Al(III), Cu(II) and Zn(II). Results shows that 1) the electron density at the two oxygen atoms of the hydroperoxide ion is highly dependent on the angle O-O-H in M-OOH species and the difference in electron density between the two oxygen atoms reaches a maximum at the angle O-O-H = 180°, 2) total electron density at the two oxygen atoms of the peroxide ion increases by approach of methane to the (hydro-peroxo)metal species in the cases of Fe(III) and Cu(II); on the other hand, significant decrease of the electron density on peroxide oxygen atoms was observed for the cases of Al(III) and Zn(II) compounds. These findings suggest that the (hydroperoxo)metal species acts as an electrophile in the former cases (M = Fe(III), Cu(II)) and as a nucleophile for the latter two compounds (M = Zn(II), Al(III)). The electrophilicity observed for the Fe(III) and Cu(II) complexes is attributed to the presence of unoccupied-or half-filled d-orbitals interacting with the hydroperoxide ion. 3) Two oxygen atoms of the (hydroperoxo)-com-pounds of Fe(III) and Cu(II) complexes exhibit quite different reactivity toward the substrate, such as methane. When methane approaches the oxygen atom which is coordinated to a metal ion, a strong decrease of electron density at the methane carbon atom occurs with concomitant increase of electron density at the peroxide oxygen atoms inducing its hetero-lytic O-O cleavage. When methane approaches the terminal oxygen atom, an oxidative coupling reaction occurs between peroxide ion and methane; at first a nucleophilic attack by the terminal electron-rich oxygen atom occurs at the carbon atom to induce C-O bond formation, and a subsequent oxidative electron transfer proceeds from substrate to the metal-peroxide species yielding CH3 -OOH, CH3OH, or other oxidized products. These results clearly de­monstrate that the (hydroperoxo)-metal compound itself is a rather stable compound, and activation of the peroxide ion is induced by interaction with the substrate, and the products obtained by the oxygenation reaction are dependent on the chemical property of the sub­ strate, redox property of a metal ion, and stability of the compounds formed in the intermediate process.

: Transition metal catalyzed cross-coupling reactions have always been very important in synthetic organic chemistry due to their versatility in forming all sorts of carbon-carbon and carbon-hetero atom bonds. Incorporation of ultrasound assistance to these protocols resulted in milder reaction conditions, faster reaction rates, etc. This review focuses on the contributions made by ultrasound-assisted protocols towards transition metal catalyzed crosscoupling reactions.

Abstract The gas generation features of coals at different maturities were studied by the anhydrous pyrolysis of Jurassic coal from the Minhe Basin in sealed gold tubes at 50 MPa. The gas component yields (C1, C2, C3, i-C4, n-C4, i-C5, n-C5, and CO2); the δ13C of C1, C2, C3, and CO2; and the mass of the liquid hydrocarbons (C6+) were measured. On the basis of these data, the stage changes of δ13C1, δ13C2, δ13C3, and δ13CO2 were calculated. The diagrams of δ13C1–δ13C2 vs ln (C1/C2) and δ13C2–δ13C1 vs δ13C3–δ13C2 were used to evaluate the gas generation features of the coal maturity stages. At the high maturity evolution stage (T > 527.6 °C at 2 °C/h), the stage change of δ13C1 and the CH4 yield are much higher than that of CO2, suggesting that high maturity coal could still generate methane. When T < 455 °C, CO2 is generated by breaking bonds between carbons and heteroatoms. The reaction between different sources of coke and water may be the reason for the complicated stage change in $$\delta^{{{13}}} {\text{C}}_{{{\text{CO}}_{{2}} }}$$ δ 13 C CO 2 when the temperature was higher than 455 °C. With increasing pyrolysis temperature, δ13C1–δ13C2 vs ln (C1/C2) has four evolution stages corresponding to the early stage of breaking bonds between carbon and hetero atoms, the later stage of breaking bonds between carbon and hetero atoms, the cracking of C6+ and coal demethylation, and the cracking of C2–5. The δ13C2–δ13C1 vs δ13C3–δ13C2 has three evolution stages corresponding to the breaking bonds between carbon and hetero atoms, demethylation and cracking of C6+, and cracking of C2–5.

An unprecedented visible-light inspired selective radical azidation of unactivated and diverse substituted vinylarenes with sulfonium iodate reagent has been realized. The intrinsic radical process triggered by light tolerated several synthetically useful functionalities enabling two new carbon-hetero bonds which display distinctive late-stage applications to biologically relevant scaffolds.

Among the realm of visible light photocatalytic transformations, late-stage difluoromethylation reactions (introduction of difluoromethyl groups in the last stages of synthetic protocols) have played relevant roles as the CF2X group substitutions exert positive impacts on the physical properties of organic compounds including solubility, metabolic stability, and lipophilicity, which are tenets of considerable importance in pharmaceutical, agrochemical, and materials science. Visible-light-photocatalyzed difluoromethylation reactions are shown to be accomplished on (hetero)aromatic and carbon–carbon unsaturated aliphatic substrates under mild and environmentally benign conditions.

AbstractSynthetic methodologies involving the formation of carbon–carbon bonds from carbon–hydrogen bonds are of significant synthetic interest, both for efficiency in terms of atom economy and for their undeniable usefulness in late-stage functionalization approaches. Combining these aspects with being metal-free, the radical C–H intermolecular arylation procedures covered by this review represent both powerful and green methods for the synthesis of (hetero)biaryl systems.1 Introduction2 Arylation with Arenediazonium Salts and Related Derivatives2.1 Ascorbic Acid as the Reductant2.2 Hydrazines as Reductants2.3 Gallic Acid as the Reductant2.4. Polyanilines as Reductants2.5 Chlorpromazine Hydrochloride as the Reductant2.6 Phenalenyl-Based Radicals as Reductants2.7 Electrolytic Reduction of Diazonium Salts2.8 Visible-Light-Mediated Arylation3 Arylation with Arylhydrazines: Generation of Aryl Radicals Using an Oxidant4 Arylation with Diaryliodonium Salts5 Arylation with Aryl Halides6 Conclusions

Over the recent years, the nucleophilic manipulation of inactivated carbon–carbon double bonds has gained remarkable credit in the chemical community. As a matter of fact, despite lower reactivity with respect to alkynyl and allenyl counterparts, chemical functionalization of isolated alkenes, via carbon- as well as hetero atom-based nucleophiles, would provide direct access to theoretically unlimited added value of molecular motifs. In this context, homogenous [Au(I)] and [Au(III)] catalysis continues to inspire developments within organic synthesis, providing reliable responses to this interrogative, by combining crucial aspects such as chemical selectivity/efficiency with mild reaction parameters. This review intends to summarize the recent progresses in the field, with particular emphasis on mechanistic details.

Regiocontrol in traditional cycloaddition reactions between unsaturated carbon compounds is often challenging. The increasing focus in modern medicinal chemistry on benzocyclobutene (BCB) scaffolds indicates the need for alternative, more selective routes to diverse rigid carbocycles rich in C(sp 3 ) character. Here, we report a palladium-catalyzed double C–H activation of two adjacent methylene units in carboxylic acids, enabled by bidentate amide-pyridone ligands, to achieve a regio-controllable synthesis of BCBs through a formal [2+2] cycloaddition involving σ bonds only (two C–H bonds and two aryl–halogen bonds). A wide range of cyclic and acyclic aliphatic acids, as well as dihaloheteroarenes, are compatible, generating diversely functionalized BCBs and hetero-BCBs present in drug molecules and bioactive natural products.

This review covers the synthetic applications of 1,4-dithianes, as well as derivatives thereof at various oxidation states. The selected examples show how the specific heterocyclic reactivity can be harnessed for the controlled synthesis of carbon–carbon bonds. The reactivity is compared to and put into context with more common synthetic building blocks, such as 1,3-dithianes and (hetero)aromatic building blocks. 1,4-Dithianes have as yet not been investigated to the same extent as their well-known 1,3-dithiane counterparts, but they do offer attractive transformations that can find good use in the assembly of a wide array of complex molecular architectures, ranging from lipids and carbohydrates to various carbocyclic scaffolds. This versatility arises from the possibility to chemoselectively cleave or reduce the sulfur-heterocycle to reveal a versatile C2-synthon.

Abstract Norbornadiene has been found useful in organic and polymer synthesis and recently its mixtures have been found useful in solar energy storage. Structure factors S(0) help to identify structure and binding at microscopic level and also play a significant role in understanding and characterizing exchanges in liquid systems. Preferential solvation Parameter δij provides information about deviation from ideal behavior for the solvent. In this work structure factors S(0) and preferential solvation Parameter δij were evaluated of binary Liquid Mixtures of Norbornadiene with Benzene, Cyclohexane, Decane, and Carbon Tetrachloride using Kirkwood Buff formalism. For the said binary mixtures experimental data pertaining to the calculations were taken from literature. Obtained results indicate that molecules which tend to form dipole interactions or hydrogen bonds form favorable interactions as seen in Norbornadiene + carbon tetrachloride where the small molecule of CCl4 is not sterically hindered to approach the polar Norbornadiene molecule. Long chain and ring structure of carbon have a negative influence on hetero interactions. Studying these parameters will develop predictive techniques to determine the right composition for optimum performance of the liquid mixture.

Sulfide linkage plays an important role not only in synthetic chemistry but also has vast applications in drug discovery as a pharmacologically active moiety. Transition metal-catalyzed thiolation is a challenging task as sulfur has a high affinity to bind with transition metal catalysts resulting in catalyst poisoning. Catalyst poisoning results in the inhibition of the reactivity and utility of the reactions. In the current work, a simple and facile method is developed to carry out S-arylation using hetero-aryl thiols and substituted aryl iodides. The reaction conditions were optimized using varied combinations of transition metal catalysts and ligands. The different copper sources included CuCl, CuI, and Cu(OAc)2 different bidentate nitrogen-based ligands including bipyridine, di-tert-butylbipyridine, DMEDA, and sarcosine. The optimized condition consists of CuI as the catalyst and DMEDA as a ligand. The reaction was found to be optimum for a range of aryl iodides in the presence highly basic oxadiazole ring. The coupled products were isolated in excellent yields and show excellent functional group tolerance bearing -NO2, -Cl, -OCF3 groups.

This study investigates the effect of exchange-correlation on the electronic properties of hybridized hetero-structured nanomaterials, called single-walled carbon boron nitride nanotubes (SWCBNNT). A first principles (ab initio) method implemented in Quantum ESPRESSO codes, together with different parametrizations (local density approximation (LDA) formulated by Perdew Zunga (PZ) and the generalized gradient approximation (GGA) proposed by Perdew–Burke–Ernzerhof (PBE) and Perdew–Wang 91 (PW91)), were used in this study. It has been observed that the disappearance of interface states in the band gap was due to the discontinuity of the π–π bonds in some segments of SWCNT, which resulted in the asymmetric distribution in the two segments. This work has successfully created a band gap in SWCBNNT, where the PBE exchange-correlation functional provides a well-agreed band gap value of 1.8713 eV. Effects of orbitals on electronic properties have also been studied elaborately. It has been identified that the Py orbital gives the largest contribution to the electrical properties of our new hybrid SWCBNNT nanostructures. This study may open a new avenue for tailoring bandgap in the hybrid heterostructured nanomaterials towards practical applications with next-generation optoelectronic devices, especially in LED nanoscience and nanotechnology.

Understanding the relationship between the formation, structure, and functionality of catalyst layers is crucial for designing catalyst layers with specific high-current-density operations. In this study, we investigated the impact of the ionomer-to-carbon (I/C) ratio and solid content on transport properties. We conducted fuel cell performance and diagnostic measurements to demonstrate the combined effects of the I/C ratio and solid content on the mass transport, particularly oxygen transport. To elucidate the roles of the I/C ratio and solid content in catalyst layer formation, we utilized dynamic light scattering and rheological measurements. By analyzing the local and global structure of ionomer-Pt/C assemblages in the catalyst inks, we observed that the I/C ratio and solid content influence the competition between homo-aggregation and hetero-aggregation, the strengths of inter- and intra-cluster bonds, and the rigidity and connectivity of the particulate structure. Additionally, high-shear-application simulations tend to reduce the connectivity of the particulate network and induce cluster densification, unless the global structure is mechanically stable and resilient. Based on this understanding, we established the formation–structure–functionality relationship for catalyst layers, thereby providing fundamental insights for designing catalyst layers tailored to specific functionalities.

It is important that chemical reactions initiated by electron transfer associated with electrodes can be achieved by precise control of intramolecular and intermolecular electron transfer of organic compounds, which is difficult to achieve by general chemical methods. Expectations for a new production process that positively controls the electron transfer is also expanding dramatically. Here, the solvent that dissolves the substrate for reaction, the network structure of the ionic species in the solution, and the role of coexisting substances are exactly grasped, and the total energy consumption is controlled under milder conditions. If it is possible to develop a chemical process that reduces the consumption of substances such as reaction reagents to the utmost while significantly suppressing the above, it is expected that structural conversion of chemical substances based on the electron transfer process can be realized. This means that advanced control of the formation, stabilization, and subsequent reactions of active open-shell molecules opens the door to new chemical reactions that reduce excess reagent and energy consumption. There is a possibility that the atom economy will be dramatically enhanced by the electron transfer reaction process for the reagents that need to be charged. This achieves a chemical reaction that is regarded as "Electrons as Reagents", and it will be a core technology that will bring about innovation in the chemical substance manufacturing method that is currently produced with the production of a large amounts of unnecessary substances and energy consumption. Research achievements: In such a background, K. Chiba pioneered original organic electrolytic reactions based on the research activities on chemical synthesis of biologically active natural compounds, and achieved various carbon skeleton formation, chemical synthesis of useful substances and biologically active natural substances. One of the notable results is the electrolytic synthesis reaction method using a unique electrolyte solution composed of lithium perchlorate / nitromethane. It was shown that the cation species generated by electrode electron transfer using this electrolyte solution are stabilized and can be applied to the formation of a wide variety of intermolecular carbon-carbon bonds. That is, numerous electrode process-triggered reactions such as varied (hetero)Diels-Alder reactions, [3+2], and [2+2] cycloaddition reactions have been achieved. In addition, the olefin metathesis without transition metal catalysis was successful for the first time. The importance of the role of the electrolyte solution in the organic electrolysis reaction was widely shown. The elucidation of these reaction mechanisms and new findings on the action of the reaction field have contributed to the rapid development of the field in recent years by utilizing and enhancing the functions of various electrolyte solutions. In addition, the application of the new organic electrolysis method has widely developed chemical synthesis methods for natural and non-natural peptides, artificial nucleic acids, etc. It is noteworthy that it was successful in electrolytic synthesis of various aza-nucleosides by utilizing the cation species under the stabilizing action of the lithium perchlorate / nitromethane electrolyte solution. This basic skeleton paves the way for mass synthesis of nucleic acid derivatives, which are promising as therapeutic drug for covid-19. Furthermore, K. Chiba achieved organic electrolytic reactions that mimic the electron transfer process in the living body. Inspired by the bio-mimic chemical reaction system, he proposed a chemical process based on biphasic solutions. The key technology is the introduction of a solution system that combines a highly polar electrolyte solution and a hydrophobic organic solvent. By controlling the temperature, phase-fusion and phase-separation can be repeated, so that the product, for example, can be taken out from the reaction system while reusing the electrolyte solution. By forming reverse micelles in a hydrophobic solvent, a continuous reaction system can be constructed, which has led to the proposal of an important method for industrial application of electrolytic reactions and of multi-step medium-size molecule syntheses reducing environmental load. Outlook for the future: We must achieve a more efficient cycle of material, food and energy to support the world's population of 9 billion in the near future. For that purpose, it is extremely important to pay attention to and apply the functions of electrons involved in the production and decomposition of all chemical substances, including the elucidation and utilization of biological functions. The key technology of controlling electron transfer is indispensable for achieving a smart green society boosting a better Anthropocene.

Isoflavones are naturally occurring compounds well-known for their beneficial role in several diseases, such as cancer and inflammation. Recently some isoflavones derivatives were reported as potent and competitive antagonists of formyl peptide receptors (FPRs) with an important role in regulating the inflammatory process. As a result of their biological activities, there is a huge interest in developing synthetic procedures to obtain isoflavones. Surprisingly, and as far as our knowledge goes, the synthetic work and full characterisation of the isoflavones described as FPR antagonists weren’t yet reported. The work herein described comprises the synthesis of two series of 2-trifluoromethyl isoflavones, including the ones described as FPR antagonists and their complete characterisation by 1D, 2D NMR techniques and high-resolution mass spectroscopy. IntroductionIsoflavones are naturally occurring compounds mainly found in soybeans, soy foods and vegetables. Chemically, they retain the typical C6C3C6 skeleton of flavonoids, consisting of two aromatic rings being linked through an oxygenated heterocycle nucleus, being isomers of flavones. They are characterised by the presence of a double bond between carbons C2 and C3 and an aromatic ring in the C3 position.1 Dietary isoflavones are well-known by their ability to act as phytoestrogens.1,2 Nevertheless, other health benefits have been attributed to this class of compounds namely, their beneficial role in cancer, such as hormone-dependent cancers, in osteoporosis, cardiovascular disease and inflammation, and several mechanisms have since been proposed to explain these activities.3 Interestingly,a series of synthetic isoflavones were recently reported as potent and competitive antagonists of formyl peptide receptors (FPRs) having an important role in the regulation of inflammatory reactions implicated in disease pathogenesis.4 Thus, the isoflavone backbone represents a promising scaffold for the development of novel FPR antagonists. As a result of their biological activity, there is a huge interest in the development of synthetic procedures to obtain isoflavones and their derivatives for structure-activity relationship studies. Surprisingly, and as far as our knowledge goes, the synthetic work and full characterisation of the synthetic isoflavones described as FPR antagonists(compounds A1, B2 and B3, figure 1), weren’t yet reported. Accordingly, the work herein described comprises the synthesis of two series of 2-trifluoromethyl isoflavones (figure 1), including the ones described as FPR antagonists and their complete characterisation by 1D and 2D NMR techniques and by high-resolution mass spectroscopy. ExperimentalMaterialsAll reagents were purchased from Sigma-Aldrich Química, S.L. and Alfa Aesar, Thermo Fisher Scientific. All solvents were pro analysis grade from Merck, Carlo Erba Reagents and Scharlab. Thin layer chromatography (TLC) was performed on pre-coated silica gel 60 F254 acquired from Merck with layer thickness of 0.2 mm. The spots were visualized under UV detection at 254 and 366 nm. Column chromatography was carried out with silica gel 60 0.040-0.063 mm acquired from Carlo-ErbaReactifs. Solvents were evaporated with a BuchiRotavapor. NMR spectroscopy 1H and 13C NMR data were acquired on a Bruker Avance III 400 NMR spectrometer operating at 400.15 MHz and 100.62 MHz, respectively. For the 1H NMR experiments, the relaxation delay was 90° pulse, spectral width of 8012 Hz and 65 K data points. In the case of the 13C NMR experiments, the corresponding parameters were 30º pulse, 24038 Hz and 65 K, respectively, and 2.0 s relaxation delay. For the Distortionless Enhancement by Polarization Transfer (DEPT) sequence, the width of the 90º pulse for 13C was 7.7 μs, and the 90º pulse for 1H was 9.8 μs; the delay 2JC, H was set to 2.0 ms. For correlation spectroscopy (COSY) and heteronuclear single quantum coherence (HSQC), the data points were set to 2 K × 256 (t2 × t1) with a relaxation delay D1 of 1.5 s. The Heteronuclear Multiple Bond Connectivity (HMBC) was acquired with data points set to 4 K × 256 (t2 × t1) and relaxation delay D1 of 1 s. Furthermore, the long-range coupling time for HMBC was set to 71 ms.The data were processed using quadratic sine-bell weighting functions in both dimensions. 1H and 13C spectra of the samples were recorded at room temperature in 5 mm outer-diameter tubes. Samples were prepared in deuterated chloroform (CDCl3). Tetramethylsilane (TMS) was used as internal reference; chemical shifts (δ) were expressed in parts per million (ppm), and coupling constants (J) were given in Hertz (Hz). The 1H and 13C chemical shifts of CDCl3 were 7.26 and 77.2 ppm, respectively. Mass spectroscopyMass spectra (MS) were carried out on a Bruker Microtof (ESI) apparatus; the data were reported as m/z (% of the relative intensity of the most important fragments). Synthesis of trifluoromethylisoflavones esters Compounds A1-A3 (Figure 1) were obtained by the cyclization of the 2-(2′-Chlorophenyl)-2′,4′-dihydroxyacetophenone, followed by its acylation with the corresponding acyl chloride, as depicted in scheme 1 (step b and c).5,6,7 Briefly, 2-(2′-Chlorophenyl)-2′,4′-dihydroxyacetophenone (1mmol) was cyclised, using trifluoroacetic anhydride (3mmol) and triethylamine (2mL). The reaction was refluxed for one hour, then poured into water, acidified (pH=3) and stirred at room temperature for another hour. The crude material was extracted with ethyl acetate (3x 10 mL). were dried over anhydrous sodium sulphate and the solvent evaporated. 7-hydroxy-3-(2-chlorophenyl)-2-(trifluoromethyl)-4H-chromen-4-one was recrystallised from ethyl acetate and obtained in a 65% yield. The acylation step was performed following the methodology described by Jayashree et al. 7: 7-hydroxy-3-(2-chlorophenyl)-2-(trifluoromethyl)-4H-chromen-4-one and (1mmol) and the corresponding acyl chloride (1.25 mmol), were dissolved in pyridine (7.5mL), and the solution refluxed for one hour (scheme 1, step c). The mixture was then cooled to room temperature and poured into water (30 mL), acidified to pH=5, and stirred at room temperature for two hours. Afterwards, the mixture was extracted with ethyl acetate (3x 10mL). The combined organic phases were dried over anhydrous sodium sulphate and the solvent evaporated under reduced pressure. The structure, chemical name, yield, and mass spectroscopy data of synthesised compounds are depicted in table I. Compounds B1-B3 (Figure 1) were obtained by the acylation of 7-hydroxy-3-(2-methoxyphenyl)-2-(trifluoromethyl)-4H-chromen-4-one with the corresponding acyl chloride, following the methodology described above and depicted in scheme 1 (step c). 7-hydroxy-3-(2-methoxyphenyl)-2-(trifluoromethyl)-4H-chromen-4-one was obtained following the procedure described in literature 8 (scheme 1, step a and b). Results and DiscussionThe complete structural characterisationof all synthesisedcompounds (A1- A3 and B1- B3) is depicted in tables II and III. The unambiguous assignment of all carbons and hydrogens was achieved by the combined expenditure of one- and two-dimensional nuclear resonance techniques. The unequivocal assignment of the NMR data for compound A1 was performed as followed: The hydrogens H-5 and H-8 of the benzopyran structure of compound A1 were readily assigned considering their splitting pattern and coupling constants (Table II). Thus, the peak at δ=8.31 ppm (d, J=8.8 Hz) was assigned to H-5 and the peak at δ=7.60 ppm (d, J=2.1 Hz) to H-8. The COSY experiment revealed an H-H interaction between these two peaks and the multiplet at δ=7.43-7.33 ppm (Figure 2), which integrated for three hydrogens. Furthermore, for this multiplet, an H-H interaction was observed with a peak at 7.52 ppm (ddd, J=0.4, 1.4, 7.9 Hz) (Figure 2). The construction of a splitting three diagram for the signal at δ=7.43-7.33 ppm enabled the identification of three hydrogens: one hydrogen at δ=7.41 ppm (H-4’, ddd, J=1.7, 7.5, 7.9 Hz), other at δ=7.39 ppm (H-6, dd, J=2.1, 8.8 Hz) and another at δ=7.35 ppm (H-5’, ddd, J=1.4, 7.4, 7.5 Hz). The COSY experiment also showed an H-H interaction between two double doublets (at δ=8.05 ppm and 7.75 ppm) with the multiplet at δ= 7.24-7.21 ppm (which integrates for two hydrogens) (Figure 2). The splitting pattern along with the coupling constants enabled the attribution of the peak at δ=8.05 ppm to H-6’’, and the peak at δ=7.75 ppm to H-4’’. Moreover, by assembling a tree diagram of the multiplet at δ= 7.24-7.21 ppm, H-5’’ and H6’ were assigned to δ=7.23 ppm. Both hydrogens showed a double doublet multiplicity. However, H6’’ showed characteristic coupling constants of a thiophene ring (J=3.8, 5.0 Hz) while H6’ presented the typical meta and orthoconstants of a phenyl ring (J=1.7, 7.4 Hz). The carbons of compound A1 were assigned using HSQC experiment and depicted in table II. The CF3 and the C-2 quaternary carbons were easily identified due to their typical coupling constants; the peak at δ= 118.9 ppm (d, J=277 Hz) was attributed to CF3, and the signal at δ= 149.4 ppm (d, J=37 Hz) was assigned as C-2. The other quaternary carbons were then assigned based on the HMBC experiment and chemical shifts with the long-range interactions summarized in Figure 3. The attribution of the quaternary carbons from the benzopyran nucleus (C-4, C-4a, C-8a, C-7) was as follows: a)The peak at δ= 175.1 ppm was assigned to C-4 due to their chemical shift and a long-range interaction with H-5; b) the long-range interaction detected between H-5 and H-8 with the peaks at δ=155.4 and 155.6 ppm allowed their attribution to C-7 and C-8a, respectively; c) a long-range interaction was detected between H-6 and the peak at δ=155.4 ppm, corroborating its assignment to C-7. Additionally, a long-range interaction of H-8 with the peak at δ=120.9 ppm was observed, which was identified as C-4a (Figure 4a). The quaternary carbons of the exocyclic phenyl ring were attributed based on the long-range correlation between the H-3’, H-4’ and H-6’ and the quaternary carbon at δ= 134.3 ppm, which was assigned to C-2’ (Figure 4b). Furthermore, the HMBC experiment showed an interaction between H-6’ and a peak at δ= 123.7 ppm, which was thus assigned as C1’. The signal at δ=159.4 ppm was assigned to carbon C-1’’ by its chemical shift and long-range interaction with H-4’’ and H-6’’. Moreover, H-4’’ and H-6’’ also showed a long-range interaction with the peak at δ=131.7 ppm, which was attributed to C-2’’ of the thiophene ring (Figure 4c). The structural assignment of compounds A2and A3 were based onthe attributions performed for compound A1.are depicted in table II. Using the same approach, the unequivocal assignment of hydrogens and carbons of the C2’-methoxyl counterparts (compounds B1-B3), was accomplished and described in table III. Nevertheless, the hydrogens of the methoxyl group were readily assigned from 1H NMR spectrum, by their chemical shift, integration and multiplicity at δ=3.77 ppm, δ=3.76 ppm and δ=3.75 ppm for compounds B1, B2 and B3, respectively. It is also important to stress that the chemical shift of exocyclic aromatic hydrogens and carbons was slightly affected by theaffected by the presence of methoxyl group at position C-2’ instead of chlorine. All the hydrogens and carbons of compounds B1- B3, with exception off C-2’, that appear with higher values of chemical shifts, suffered an upfield chemical shift, while C-2’ appears at relative to their C2’-Cl counterparts (compounds A1- A3). Table II: 1H and 13C NMR Data of Compounds A1-A3 Table I: 1H and 13C NMR Data of Compounds B1-B ConclusionsThis work describes for the first time an effective synthetic strategy to obtain trifluoromethylisoflavones derivatives, namely the ones that were described as FPR antagonists.4Theisoflavones(compounds A1-A3 and B1-B3) were synthesised in good yields and had been fully characterised by homo- and hetero-nuclear NMR and high-resolution mass spectrometry. The acquired data allowed the unambiguous identification of these compounds, providing a valuable database for the unequivocal identification of other analogue libraries. AcknowledgmentsThis work was funded by FEDER funds through the Operational Programme Competitiveness Factors-COMPETE and national funds by FCT – Foundation for Science and Technology under research grants (QUI/UI0081/2013, NORTE-01-0145-FEDER-000028 and PTDC/DTP-FTO/2433/2014). A. Gaspar (SFRH/BPD/93331/2013) grant is supported by FCT, POPH and QREN. References Szeja, W.; Grynkiewicz, G.; Rusin, A. “Isoflavones, their Glycosides and Glycoconjugates. Synthesis and Biological Activity”. Curr Org Chem. 2017, 21(3), 218-235. Vitale, DC.; Piazza, C.; Melilli, B.; Drago, F.; Salomone, S. “Isoflavones: Estrogenic activity, biological effect and bioavailability”. Eur J Drug Metab Pharmacokinet. 2013, 38, 15–25. Jie Yu, J.; Bi, XJ.; YU, B.; Chen, D. “Isoflavones: Anti-Inflammatory Benefit and Possible Caveats” 2016, 8(6), 361. Schepetkin, IA.; Kirpotina, LN.; Khlebnikov, AI.; Cheng, N.; Ye, RD. “Antagonism of human formyl peptide receptor 1 (FPR1) by chromones and related isoflavones”. 2014, 92, 627–641. Balasubramanian, S.; Nair, MG. “An Efficient “One Pot” Synthesis of Isoflavones”. Synth Commun. 2000, 30(3), 469-484. Eiffe, E.; Heaton, A.; Walker, C.; Husband, A. “2-Substituted isoflavonoidcompounds, medicaments and uses”. 2009, WO 2009003229 A1. Jayashree, BS.; Thejaswini, JC.; Nayak, Y.; Kumar, DV. “Synthesis of Novel Flavone Acyl Esters and Correlation of log P Value with Antioxidant and Antimicrobial Activity”. Chem Asian J. 2010, 22(2), 1055-1066. John NicolsonLow, J. N.; Ligia R. Gomes, L.R.; Alexandra Gaspar, A.; Borges. “Structure of 7-hydroxy-3-(2-methoxyphenyl)-2-trifluoromethyl-4H-chromen-4-one”. Acta Crystallogr E Crystallogr Commun. 2017, 73, 1130–1134.

AbstractDirecting group assisted C−H bond functionalization using transition‐metal‐catalysis has emerged as a reliable synthetic tool for the construction of regioselective carbon‐carbon/heteroatom bonds. Off late, “in/on water directed transition‐metal‐catalysis”, though still underdeveloped, has appeared as one of the prominent themes in sustainable organic chemistry. This article covers the advancements, mechanistic insights and application of the sustainable directed C−H bond functionalization of (hetero)arenes in/on water in the presence of transition‐metal‐catalysis.

Transition‐metal catalyzed difunctionalization of olefins has attracted considerable attention as a method to construct carbon‐carbon and carbon‐hetero bonds. Herein, the copper‐catalyzed three‐component radical cross‐coupling of oxime esters, styrenes, and AgSCF3 through a visible‐light‐promoted iminyl radical‐mediated carbon‐carbon bond cleavage strategy has been described. Utilizing low‐cost copper salt as both photosensitizers and cross‐couplers, this protocol delivers diverse target products, providing a supplementary approach for cyanoalkylation and trifluoromethylthiolation of drug molecules.

Controlling various reactions by multiple weak interactions or soft forces has become an widespread topic under supramolecular catalysis. This review has made a literature collection that explores cooperative weak or noncovalent interactions. These are charge transfer complexation, H-bonding, S-H…π, acid-base, cation- π, etc., towards C-hetero bond formation reactions. This review article will discuss the specific reactivity of chemical systems controlled by weak interactions.

AbstractThis Account summarizes the highly appealing dearomatization reactions of β-naphthols for the synthesis of highly functionalized, three-dimensional structures starting with simple planar aromatic compounds. The reactions are categorized mainly from the viewpoint of the construction of carbon–hydrogen, carbon–carbon, and carbon–hetero bonds (C–N/O, C–Cl, C–F) at the α-position of β-naphthols. The dearomatized products play an important role in organic synthesis and materials science.1 Introduction2 Construction of Carbon–Hydrogen Bonds at the α-Position of β-Naphthols3 Construction of Carbon–Carbon Bonds at the α-Position of β-Naphthols4 Construction of Carbon–Nitrogen/Oxygen Double Bond at the α-Position of β-Naphthols5 Construction of Carbon–Carbon and Carbon–Oxygen Bonds at the α-Position of β-Naphthols6 Construction of Carbon–Halogen Bonds at the α-Position of β-Naphthols7 Conclusion

A series of three ruthenabenzenes acting as hetero-arene ligands towards a second Ru centre was synthesized from a dimetallic precursor via double C–C bond coupling between allenyl, carbon monoxide and alkyne units.

Abstract: Among the several peroxides available, meta-chloroperbenzoic acid (mCPBA) plays an efficient role of oxidizing reagent and is used for many oxidative transformations, such as oxidation of various functional groups, carbon-carbon, carbon-hetero bond formation, heterocyclic ring formation, heteroarylation, oxidative cross-coupling, lactonization, oxidative dearomatization, α-oxytosylation or α-acetoxylation, oxidative C-C bond activation and in other miscellaneous reactions. The purpose of this review is to critically discuss the significant contributions of mCPBA along with hypervalent iodine/iodine reagents in organic synthesis from mid-2015 to date.

Abstract Antiviral medications are a branch of medicines notably used to treat that cause many significant diseases in humans and animals. This monograph mainly focuses on recent developments and synthesis of antiviral drugs using carbon-carbon and carbon–hetero bond cross-coupling chemistry. Viral infections exact several severe human diseases, accounting for remarkably high mortality rates. In this sense, academia and the pharmaceutical industry continuously search for novel compounds with better antiviral activity. The researchers face the challenge of developing greener and economical ways to synthesize these compounds and make significant progress.

Abstract Conserving the environment is one of the most imperative goals in recent days among the chemists throughout the world. Swiftly increasing the environmental awareness also increases the demand to build new approaches for synthesizing the same active molecules with zero-waste and pollution. In this background, visible-light-mediated synthesis and functionalization of diverse organic compounds has been established as a tremendously successful topic and has achieved a remarkable stage of superiority and efficiency in the last 20 years. Alternatively, organosilicon derivatives are gradually aspiring leaves among chemists because of their significant application on synthetic, medicinal, and material chemistry. In this scenario, the addition of Si–H group to carbon−carbon multiple bonds (alkenes, hetero-arenes, alkynes, allenes, carboxylic acids, enynes, and dienes) provides an extremely step- and atom-efficient method to obtain silicon-containing compounds. Several attempts for the development of mild, robust, and efficient green protocol were taken in the last two decades. In spite of substantial advancement/research on C–Si bond formation using transition metal catalysis, a green and metal-free approach is highly essential considering its application in the field of medicine and with respect to environmental aspects as well. In this article, we will summarize the reports considering suitable visible-light-mediated metal-free silylation of C–C multiple bonds that includes alkenes, hetero-arenes, alkynes, allenes, enynes, and dienes.

Cobalt-catalyzed hydroalkynylation of alkynes, alkenes, and imines affords internal alkynes with various functional groups adjacent to the carbon-carbon triple bond moiety in an atom-economical manner. In addition, cross-coupling of in situ-generated alkynylcobalt species from terminal alkynes, haloalkynes, and metal acetylides with (hetero)aromatic compounds and organic halides selectively provides various internal aryl- and alkylalkynes. 1 Introduction 2 Hydroalkynylation of Alkynes for 1,3-Enyne Synthesis 3 Hydroalkynylation of Polar and Non-polar Double Bonds 4 Dehydrogenative Cross-coupling Reaction Using Terminal Alkynes with Aromatic Compounds 5 Cross-coupling Reactions Using Haloalkynes as the Coupling Partners 6 Cross-coupling Reactions Using Metal Acetylides 7 Conclusion

Attempts to carry out intramolecular annulation of 9,10‐diarylbenzo[h]quinolines and 9,10‐di(hetero)arylphenanthrenes to aromatics with expanded p‐conjugated systems by using different methods are described. The starting compounds (9,10‐diarylbenzo[h]quinolines and 9,10‐di(hetero)arylphenanthrenes) were prepared by C‒C bond activation in 1‐azabiphenylene or biphenylene followed by insertion of internal alkynes. Interestingly, unlike in purely carbon‐based aromatics, the course of the annulation turned out to be highly dependent on the structure of maternal compounds. In a handful of cases were obtained the expected or desired products. In others, unexpected rearrangements of the basic molecular frameworks were observed.

Transition-metal catalysis has been consequential in enabling carbon-heteroatom bond-forming reactions. Recent breakthroughs in Ni-catalyzed cross-couplings have offered competitive, and in some cases superior, reactivity to Pd- or Cu-based processes. Amidst the ongoing renaissance in this field, the Ni-catalyzed C-O cross-coupling of alcohols and (hetero)aryl (pseudo)halides has surfaced as an effective strategy for the synthesis of (hetero)aryl ethers. Methodologies to achieve such transformations tend to rely on one of three catalytic approaches: (i) thermal conditions often accompanied by ancillary ligand design tailored for Ni catalysis; (ii) the synergistic combination of photoredox and Ni catalysis; or (iii) electrochemically driven Ni catalysis. In some instances, these protocols have provided access to expanded C-O cross-coupling substrate scope, including the use of inexpensive and abundant electrophile coupling partners (e.g., (hetero)aryl chlorides). This Review aims to summarize recent progress in the development of Ni-catalyzed O-arylations of primary, secondary, and tertiary aliphatic alcohols, as well as phenols, with (hetero)aryl electrophiles.

AbstractConstructing low-dimensional covalent assemblies with tailored size and connectivity is challenging yet often key for applications in molecular electronics where optical and electronic properties of the quantum materials are highly structure dependent. We present a versatile approach for building such structures block by block on bilayer sodium chloride (NaCl) films on Cu(111) with the tip of an atomic force microscope, while tracking the structural changes with single-bond resolution. Covalent homo-dimers in cis and trans configurations and homo-/hetero-trimers were selectively synthesized by a sequence of dehalogenation, translational manipulation and intermolecular coupling of halogenated precursors. Further demonstrations of structural build-up include complex bonding motifs, like carbon–iodine–carbon bonds and fused carbon pentagons. This work paves the way for synthesizing elusive covalent nanoarchitectures, studying structural modifications and revealing pathways of intermolecular reactions.

AbstractCopper-mediated carbon–heteroatom bond-forming reactions involving a wide range of substrates have been in the spotlight for many organic chemists. This review highlights developments between 2010 and 2019 in both stoichiometric and catalytic copper-mediated reactions, and also examples of nickel-mediated reactions, under modified Chan–Lam cross-coupling conditions using various nucleophiles; examples include chemo- and regioselective N-arylations or O-arylations. The utilization of various nucleophiles as coupling partners together with reaction optimization (including the choice of copper source, ligands, base, and other additives), limitations, scope, and mechanisms are examined; these have benefitted the development of efficient and milder methods. The synthesis of medicinally valuable or pharmaceutically important nitrogen heterocycles, including isotope-labeled compounds, is also included. Chan–Lam coupling reaction can now form twelve different C–element bonds, making it one of the most diverse and mild reactions known in organic chemistry.1 Introduction2 Construction of C–N and C–O Bonds2.1 C–N Bond Formation2.1.1 Original Discovery via Stoichiometric Copper-Mediated C–N Bond Formation2.1.2 Copper-Catalyzed C–N Bond Formation2.1.3 Coupling with Azides, Sulfoximines, and Sulfonediimines as Nitrogen­ Nucleophiles2.1.4 Coupling with N,N-Dialkylhydroxylamines2.1.5 Enolate Coupling with sp3-Carbon Nucleophiles2.1.6 Nickel-Catalyzed Chan–Lam Coupling2.1.7 Coupling with Amino Acids2.1.8 Coupling with Alkylboron Reagents2.1.9 Coupling with Electron-Deficient Heteroarylamines2.1.10 Selective C–N Bond Formation for the Synthesis of Heterocycle-Containing Compounds2.1.11 Using Sulfonato-imino Copper(II) Complexes2.2 C–O Bond Formation2.2.1 Coupling with (Hetero)arylboron Reagents2.2.2 Coupling with Alkyl- and Alkenylboron Reagents3 C–Element (Element = S, P, C, F, Cl, Br, I, Se, Te, At) Bond Forma tion under Modified Chan–Lam Conditions4 Conclusions

AbstractAromaticity generally describes a cyclic structure composed of sp2-hybridized carbon or hetero atoms with remarkable stability and unique reactivity. The doping of even one sp3-hybridized atom often damages the aromaticity due to the interrupted electron conjugation. Here we demonstrate the occurrence of an extended hyperconjugative aromaticity (EHA) in a metalated indole ring which contains two gem-diaurated tetrahedral carbon atoms. The EHA-involved penta-aurated indolium shows extended electron conjugation because of dual hyperconjugation. Furthermore, the EHA-induced low electron density on the indolyl nitrogen atom enables a facile protodeauration reaction for the labile Au-N bond. In contrast, the degraded tetra-aurated indolium with a single gem-dimetalated carbon atom exhibits poor bond averaging and inertness in the protodeauration reaction. The aromaticity difference in such two polyaurated indoliums is discussed in the geometrical and electronic perspectives. This work highlights the significant effect of metalation on the aromaticity of polymetalated species.

AbstractA regioselective carbosilylation of alkenes has emerged as a powerful strategy to access molecules with functionalized silylated alkanes, by incorporating silyl and carbon groups across an alkene double bond. However, to the best of our knowledge, organic fluorides have never been used in this protocol. Here we disclose the catalyst-free carbosilylation of alkenes using silyl boronates and organic fluorides mediated by tBuOK. The main feature of this transformation is the selective activation of the C-F bond of an organic fluoride by the silyl boronate without undergoing potential side-reactions involving C-O, C-Cl, heteroaryl-CH, and even CF3 groups. Various silylated alkanes with tertiary or quaternary carbon centers that have aromatic, hetero-aromatic, and/or aliphatic groups at the β-position are synthesized in a single step from substituted or non-substituted aryl alkenes. An intramolecular variant of this carbosilylation is also achieved via the reaction of a fluoroarene with a ω-alkenyl side chain and a silyl boronate.

Abstract:: The use of small organic molecules as organocatalysts in organic synthesis has intensely studied over the past decade. In this emerging field, considerable study has led to the introduction of various efficient organocatalyzed synthetic methods of carbon-carbon and carbon-hetero atom bond formations. The use of these organocatalysts also emerged environmentally benign reaction conditions compared to the metal catalyzed transformations. In this review, we make a special attention on the most recent organocatalytic protocols reported for the synthesis of heterocycles. The works have been outlined by depending on the organocatalysts used as (i) nitrogen based molecules as organocatalyst, (ii) NHCs as organocatalyst, and (iii) phosphorus based molecules as organocatalyst. The discussion intends to reveal the scope as well as vitality of organocatalysis in the area of heterocycle synthesis.

The C(sp3)‐H bond decyanative arylations of diverse symmetrical and unsymmetrical BIMs have been successfully accomplished. Aromatic nitriles were utilized as components in the presence of thiobenzoic acid (TBA) under visible‐light irradiation. These redox‐neutral protocols provide a highly efficient and practical strategy for the synthesis of a broad range of bis(indolyl)‐substituted and mono(indolyl)‐substituted hetero‐triarylmethanes. Moreover, this synthetic approach has been expanded to the construction of indole‐substituted triarylmethanes bearing all‐carbon quaternary stereocenters. It is noteworthy that the preparation of the natural product Arsindolin A was effectively achieved using this methodology.

Iron integrated graphitic carbon nitride (GCN) was synthesized by adopting co‐precipitation method. No appreciable change in XRD main peak of both GCN and Fe(III)‐GCN indicates the lattice structure remains the same and there is no bulk doping of Fe(III). More sharp IR bands of Fe(III)‐GCN between 1000 and 1750 cm−1 compared with GCN reflect ordered packing of tri‐s‐triazine units in the nanosheets. Scanning electron microscopy (SEM) analysis reveals less thin and large two dimensional sheets have formed from bulk GCN during catalyst preparation. The absence of bright spots in transmission electron microscopy (TEM) indicates that there is no crystalline metal oxide phase confirming that iron(III) is present as ions. Fe(III)‐GCN was then exploited as an efficient heterogeneous catalyst for the synthesis of bis (hetero/homoarylidene)cycloalkanones from heteroaromatic/homoaromatic carbaldehydes and cycloalkanone through carbon–carbon double bond construction. The reaction effected well in water, a green solvent as a reaction medium at ambient temperature. The catalytic competency exposed good performance towards reusability. Added advantages include easy preparation and inexpensiveness.

Type I aldolases catalyze carbon-carbon bond-forming reactions to form a diverse set of products in nature but often display high selectivity for their natural substrates. One such aldolase, NahE, is known to catalyze the condensation of pyruvate with a wide range of aldehydes to give trans-4-phenyl-2-oxo-3-butenoic acids under mild aqeuous conditions. These ,-unsaturated 2-oxo acids are versatile intermediates for synthetic transformations. NahE has also been used for the synthesis of α-fluoro-β-hydroxy esters, β-hydroxy esters, and quinaldic acids. However, a thorough study of the substrate scope on a practical scale has not been performed for the native NahE-catalyzed aldol condensation reaction. Here we report that NahE can accept >35 (hetero)aromatic and aliphatic aldehydes. Most condensation products derived from substituted benzaldehydes were isolated in >95% yield without need for further purification, while non-benzaldehyde substrates gave the corresponding products in isolated yields between 26 and 98%. Reactions could be performed on gram scale. These products could be converted to α,β-unsaturated carboxylic acids in up to 93% yield over two steps. This reaction sequence was also performed using whole cells in up to 79% yield. This work demonstrates that NahE is a robust, efficient, and versatile catalyst for organic synthesis.