Academic literature on the topic 'Alkenes – Synthesis; Metal catalysts; Complex compounds'

The complexes of iron are found to be too reactive and are too diverse in their reactivity, when compared to the other neighbouring metals in the group. Iron complexes are used in various catalytic reactions such as oxygenation of C–H bonds, the oxidation of alcohols to aldehydes, ketones (or) carboxylic acids, the epoxidation or dihydroxylation of alkenes and oxidative coupling reactions. Efforts are taken to avoid certain disadvantages taking place during enzymatic catalysis such as the temperature and solvent sensitivity, narrow substrate scope, restricted accessibility and so on observed while using other catalysts via iron enzymes. This helped in the various synthesis of complex molecules by increase in the number of iron catalyst systems for the oxidation reactions.

Among the variety of sulfonamides, triflamides (CF3SO2NHR, TfNHR) occupy a special position in organic chemistry. Triflamides are widely used as reagents, efficient catalysts or additives in numerous reactions. The reasons for the widespread use of these compounds are their high NH-acidity, lipophilicity, catalytic activity and specific chemical properties. Their strong electron-withdrawing properties and low nucleophilicity, combined with their high NH-acidity, makes it possible to use triflamides in a vast variety of organic reactions. This review is devoted to the synthesis and use of N-trifluoromethanesulfonyl derivatives in organic chemistry, medicine, biochemistry, catalysis and agriculture. Part of the work is a review of areas and examples of the use of bis(trifluoromethanesulfonyl)imide (triflimide, (CF3SO2)2NH, Tf2NH). Being one of the strongest NH-acids, triflimide, and especially its salts, are widely used as catalysts in cycloaddition reactions, Friedel–Crafts reactions, condensation reactions, heterocyclization and many others. Triflamides act as a source of nitrogen in C-amination (sulfonamidation) reactions, the products of which are useful building blocks in organic synthesis, catalysts and ligands in metal complex catalysis, and have found applications in medicine. The addition reactions of triflamide in the presence of oxidizing agents to alkenes and dienes are considered separately.

An efficient and straightforward protocol to complex indene-based polycyclic compounds via the cascade cyclization of propargylic alcohols and alkenes was developed. The catalyst FeCl₃, as an Earth-abundant and environment friendly transition metal salt, is attractive. This reaction proceeded through unusual C–C bond cleavage.

Based on an analysis of the literature published from the late 20th century to the beginning of the 21st century, methods for the synthesis of some complex tetraorganylphosphonium salts are systematized and described, along with the features of the chemical transformations of pentaphenylphosphorus, which was first obtained in 1953. The tetraorganylphosphonium salts were known much earlier, however, the features of the synthesis of transition metal complexes, which are usually obtained from tetraorganylphosphorus halides and metal halides, have not been sufficiently studied. The present review is devoted to the discussion of these topics, since the famous Wittig Reaction is associated with aryl phosphorus compounds, which allows synthesizing alkenes of a given structure, and derivatives of transition metals rightfully occupy a special place among catalysts of various chemical processes. The continuation of these classical studies in the field of chemistry of organoelemental compounds takes place at one of the leading universities in Russia - South Ural State University in the laboratory of chemistry of organoelemental compounds at the Faculty of Chemistry. This article aims at familiarizing the reader with the achievements of Professor V.V. Sharutin and his students in the field of organophosphorus compounds. The main attention is paid to the reactions of pentaphenylphosphorus and its derivatives, as well as methods for the synthesis of ionic complexes of silver, gold, copper, titanium, zirconium, hafnium, ruthenium, osmium, cobalt, rhodium, iridium, palladium and platinum with tetraorganylphosphonium cations. The structural features of the described compounds and the possibility of using transition metal complexes in some catalytic reactions are described.

In accordance with United Nations General Assembly resolution, the year 2019 was proclaimed the International Year of the Periodic Table of Chemical Elements. Rare-earth elements were discovered during the time of the Periodic System development. In the past few decades, their compounds have attracted great interest due to their unique reactivity. This review covers recent achievements in the field of intermolecular hydrophosphination of alkenes, dienes and alkynes, which is catalyzed by rare earth and alkaline-earth metal complexes. Catalytic hydrophosphination reaction is the addition of an P—H bond to С—С multiple bonds, and offers an efficient and elegant synthetic approach to production of the organophosphorus compounds widely used in industrial synthesis, pharmaceuticals, agrochemistry, and other areas. The high values of the ionic radii of rare earth and alkaline-earth metals in combination with the Lewis acidity provide their compounds with a pronounced tendency to complex formation and, accordingly, high coordination numbers. Due to high reactivity of M—E (E = C, H, N, P) bonds, ease of Ln—P ı-bond metathesis and multiple C—C bond insertions, these compounds offer new prospects for the catalysis of the alkenes and alkynes hydrophosphination. Therefore, complexes of non-toxic and relatively abundant in nature rare earth and alkaline earth metals can be a cheaper and more effective alternative to compounds of late transition metals in the catalysis of the C—P bond formation.

Oxygen atom incorporation into organic molecules is one of the most powerful strategies to increase their pharmacological activity and to obtain valuable intermediates in organic synthesis. Traditional oxidizing agents perform very well, but their environmental impact and their low selectivity constitute significant limitations. On the contrary, visible-light-promoted oxygenations represent a sustainable method for oxidizing organic compounds, since only molecular oxygen and a photocatalyst are required. Therefore, photocatalytic oxygenation reactions exhibit very high atom-economy and eco-compatibility. This mini-review collects and analyzes the most recent literature on organo-photocatalysis applications to promote the selective oxygenation of organic substrates. In particular, acridinium salts, Eosin Y, Rose Bengal, cyano-arenes, flavinium salts, and quinone-based dyes are widely used as photocatalysts in several organic transformations as the oxygenations of alkanes, alkenes, alkynes, aromatic compounds, amines, phosphines, silanes, and thioethers. In this context, organo-photocatalysts proved to be highly efficient in catalytic terms, showing similar or even superior performances with respect to their metal-based counterparts, while maintaining a low environmental impact. In addition, given the mild reaction conditions, visible-light-promoted photo-oxygenation processes often display remarkable selectivity, which is a striking feature for the late-stage functionalization of complex organic molecules.

1,2-Dihaloalkenes readily undergo simultaneous or sequential difunctionalization through transition-metal-catalyzed reactions, which makes them attractive building blocks for complex unsaturated motifs. This review summarizes recent applications of such transformations in C–C and C–heteroatom bond forming processes. The facile synthesis of stereodefined alkene derivatives, as well as aromatic and heteroatomic­ compounds, from 1,2-dihaloalkenes is thus outlined.1 Introduction2 Synthesis of 1,2-Dihaloalkenes3 C–C Bond Forming Reactions4 C–Heteroatom Bond Forming Reactions5 Conclusion

The study of the properties and use of natural metalloporphyrins in the development of new highly selective methods for the oxygenation of hydrocarbons at moderate temperatures is an urgent problem. The present work is devoted to the extraction of metalloporphyrins from oil residues and the creation on their basis of effective catalytic systems for the oxidation of alkenes. The separation of metalloporphyrins from oil residues was carried out using new bifunctional organic extractants having the nature of keto-alcohols and providing a greater degree of extraction of porphyrins in comparison with the known traditionally used extractants. The results of a study of a number of new bifunctional organic reagents as extractants for the selective extraction of oil porphyrins from asphaltenes are presented, their spectral characteristics are studied, the dependence of the degree of extraction on the mass ratio of the extractant and the crude oil is revealed. The best results were obtained with a mass ratio of 1:30. The isolated mixture of metalloporphyrins is first subjected to demetallization with hydrochloric acid (pH=1–2), turning into a mixture of porphyrins, then, to obtain individual metal porphyrin complexes, the required transition metal ions are introduced into the porphyrin ring by treating the mixture with these metal salts. It was shown that the yield of synthesized oil porphyrins is 42–85 %, depending on the nature of the metal. The composition and structure of the synthesized oil metalloporphyrins containing iron, cobalt, nickel, manganese are established by modern methods of physico-chemical analysis. The catalytic properties of synthesized metalloporphyrins in the epoxidation of unsaturated alkenes have been investigated. Their dioxide adducts were obtained, and a mechanism was proposed for the oxidation of alkenes with the formation of oxinoid structures as a result of the decomposition of the oxygen complexes of metal porphyrins

The enantioselective synthesis of a bicyclo[4.3.0]nonene derivative bearing a quaternary carbon stereocenter is achieved by employing a desymmetrization strategy involving an intramolecular addition. The intramolecular nucleophilic addition of a highly reactive carbanion generated from an alkenyl iodide in the presence of a chiral ligand occurs with discrimination of two keto carbonyl groups to give the corresponding bicyclic compound in 81% yield and 39% ee. Asymmetric synthesis via an intramolecular desymmetrization strategy using a chiral ligand–carbanion complex represents a complementary approach to using chiral organocatalysts or chiral ligand–transition-metal complexes.

The mechanism of gold(III)-catalyzed 1,3-dipolar [[Formula: see text]] cycloaddition reactions of 2-(1-alkynyl)-2-alken-1-ones with nitrones to afford highly-substituted furo [3,4-d] [1,2] oxazines, which are useful as structural skeletons in biologically active compounds and as synthetic building blocks in organic synthesis, have been studied computationally. The results show that the reaction proceeds via the formation of a [Formula: see text]-complex in which the gold moiety coordinates to the triple bond of the 2-(1-alkynyl)-2-alken-1-ones, resulting in an intramolecular cyclization of the gold intermediate to generate a carbocation intermediate which is trapped by the nucleophilic oxygen of the nitrone to form a furanyl–gold complex, which upon subsequent cyclization affords the furo [3,4-d] [1,2] oxazine as well as regenerates the gold catalyst. The highest activation barrier in the entire cycle is 19.5[Formula: see text]kcal/mol which accompanies the intramolecular cyclization step. The activation barriers for the reactions of 2-(1-alkynyl)2-alken-1-ones with electron-donating and cyclic substituents are generally lower compared to those of the parent 2-(1-alkynyl)2-alken-1-one while the reactions of 2-(1-alkynyl)2-alken-1-ones with electron-withdrawing substituents have higher activation barriers. Preliminary exploratory calculations on the possibility of replacing gold, an expensive and rare metal, with a copper-based catalyst for the reaction, show that for the key elementary steps, the Cu (III) catalyst is at least as active as the Au (III) complex, thus providing a cheaper route to furo [3,4-d] [1,2] oxazine.

The prevalence of fluorine in natural products is scarce. There are but a handful of compounds that have been discovered to date. This could be largely attributable to the occurrence of fluorine in nature as fluoride (F-). — One might recognize such nomenclature from the ingredients list on a toothpaste tube — In fact, naturally occurring fluoride is most commonly found as fluorite (CaF2) or cryolite (Na3AlF6). As such, the introduction of fluorine via biological pathways has been limited to use of aqueous F- (a very poor nucleophile). This fact — coupled with its naturally low concentration in water — has created the ripe conditions for this shortage. In a way this has proven fertile for synthetic chemists because nature has not yet evolved a method for the deconstruction of partially or fully fluorinated compounds. Considering the above, as synthetic methodologies for the construction of carbon-fluorine bonds became available, so too did the discovery of their valuable properties. So beneficial are these properties that C-F bond-containing compounds have become commonplace in many households throughout the world. For example, practically every home relies on these compounds for use in their refrigerators. Other examples of useful fluorinated materials include blowing agents, non-stick coatings, pharmaceuticals, agrochemicals, liquid crystals, and lubricants. With all these applications and seemingly easy availability of these compounds, it is interesting to learn that original synthetic methods are still being employed today. As such, the objective of this Thesis is to develop ‘greener’ routes for the synthesis of fluorocarbons. We hypothesized that by studying transition metal-fluoroalkyl complex-mediated reactions, a more efficient catalytic system could be developed. A foreseen complication arises from the thermodynamic stability of C-F, transition metal-F and transition metal-CRF bonds. Improvements to overcome these caveats include the use of first-row late transition metal complexes. Presented herein are additions to this body of knowledge by expanding on the reactivity of nickel, copper and silver fluoroalkyl complexes. The approach applied in this work, in line with ‘green’ chemistry principles, was to source readily available fluorinated reagents, i.e. fluoroalkenes and fluoroarenes, to reduce the number of steps for the synthesis of new fluorinated compounds. Chapter 2 builds on the well-established oxidative cyclization of C2 fluoroalkenes to nickel (0), which yields new C4 units. The use of a bulky N-heterocyclic carbene ligand was found to enhance reactivity by reducing the coordination number at nickel. Examples of room temperature Cα-F and Ni-CF bond activation and functionalization reactions are presented. Chapters 3, 4 and 5 re-examine the insertion of fluoroalkenes into silver and copper fluorides and hydrides. Building on precedent of addition reactions to hexafluoropropene, this fluoroalkene was examined first. In so doing, a versatile and inexpensive copper heptafluoroisopropyl reagent was developed (Cu-F addition to (CF3)CF=CF2. With easy access to new heptafluoroisopropyl complexes, they were systemically studied for their applications in catalysis. This revealed key features, particularly the lability of the M-hfip bond, which could be detrimental to catalytic reactions. As such, a nickel complex-mediated carbonylative heptafluoroisopropylation reaction and copper complex-mediated nucleophilic addition to electrophiles were developed. When a copper hydride was used instead, the in situ generated fluoroalkyl [Cu-H addition to (CF3)CF=CF2] was susceptible to β-fluoride elimination. Chapter 4 expands this methodology to achieve the catalytic consecutive hydrodefluorination of fluoroalkenes, demonstrating the scope and limitations of this system. Furthermore, the critical role of the phosphine ligand in accessing an L3Cu-H addition and unusual β-fluoride elimination mechanism is highlighted. However, tetrafluoroethylene proved resistant to this reaction because the fluoroalkyl resting state of this alkene, Cu-CF2CF2H, is unusually robust. Chapter 5 investigates the utility of this fragment and others in C(sp2)-RF cross-coupling and nucleophilic substitutions. With focus on new routes for late stage fluorination and examples of nickel (0) complex-catalyzed selective C-F bond functionalization reactions, Chapter 5, continues studies for low-temperature and DMAP-assisted conditions for aryl-F cross-coupling reactions with boronic acid esters. Lastly, Chapter 6 reviews the advances presented in this Thesis, provides a link to the expected lasting impacts and attempts to provide guidance to future research on transition-metal complexes in the synthesis of C-F or C-RF containing compounds. Moreover, with the introduction of a new hydrodefluorination technology, previously scarce fluoroalkenes (e.g. 1,2-difluoroethylene) can now be used more freely, potentially leading to the development of new refrigerants or materials applications.

The development of procedures for the synthesis of valuable organic molecules constitutes an important part of chemistry. The goal of improving the efficiency of existing methodologies can be fulfilled by use of metal catalysts. Recent developments in the field of homogeneous gold catalysis have contributed to these efforts and continued investigations assure future innovations. Chapter 1 summarises the properties of gold and ligand-supported gold(I) complexes and demonstrates how a detailed understanding of its reactivity and possible bonding interactions with various substrates facilitates the development of well-defined catalytic systems. Particular attention is given to N-heterocyclic carbenes, highly tunable ligands that stabilise a wide range of different transition metal complexes. Three chapters describe syntheses and studies of known and new complexes. Chapter 2 discusses expedient syntheses of key NHC-gold(I) complexes and catalysts. Chapter 3 constitutes studies to the behaviour of the commonly used tetrafluoroborate counterion in a particular IPrCl -gold(I) complex. Chapter 4 de- scribes the synthesis of a range of IPr-gold(I) carbanion complexes from the widely studied IPr-gold(I) hydroxide synthon, the study of their properties and exploration of their reactivity. Catalytic applications in transformations of alkynes and alcohols are described in the last three chapters. Chapter 5 details the development of efficient NHC-gold(I)-catalysed procedures for the synthesis of vinyl ethers through addition reactions of aliphatic and benzylic alcohols to alkynes. Benzylic alcohols were found to undergo gold-catalysed dehydration under specific conditions and Chapter 6 discloses the NHC-gold(I)-catalysed dehydrative formation of ethers from phenols and benzylic alcohols. Appendix A describes preliminary explorations to the complimentary use of Brønsted acidic compounds as catalysts for the formation of products with new C – C bonds from benzylic alcohols and phenols.

The work described herein focuses on the synthesis and characterisation of copper(I) complexes bearing N-heterocyclic carbene (NHC) ligands, their use in catalysis as well as organometallic synthesis and related reaction mechanisms. Two classes of complexes were considered: neutral NHC-Cu(I) species and their cationic analogues. Concerning the former, initial efforts were focused on the development of a general and straightforward synthetic methodology towards complexes of the type [Cu(X)(NHC)] (X = Cl, Br, I). More than 10 NHC-Cu(I) species were synthesised in high yields under mild conditions, in air and using technical grade solvents. These complexes exhibited interesting activity in the catalytic dehydrogenation of formic acid/amine adducts proving in three times more efficiency than the copper salts previously employed in such a reaction. Hydroxide- and tert-butoxide analogues showed to be efficient catalysts in the N-methylation of amines with CO₂ as carbon source, and in the dehydrogenative coupling of silanes and carboxylic acids. Experimental and computational work were carried out in order to elucidate the mechanism of these transformations. Regarding the use of these species in organometallic synthesis, homo- and heteroleptic bis-NHC-Cu(I) complexes were employed as carbene transfer reagents to other transition metals. Aside from well-known cationic gold(I) species, two novel palladium(II) analogues were isolated and fully characterised.

Includes a list of publications by the author arising from this thesis.
Bibliography: leaves 174-176.
178 leaves : ill. ; 30 cm.
Studies the reactivity of metal alkynyl fragments, in particular the formation of compounds containing two or more alkynes, resulting in the preparation of complexes with interesting properties and reactivities.
Thesis (Ph.D.) -- University of Adelaide, Dept. of Chemistry, 2001

Includes a list of publications by the author arising from this thesis.
Bibliography: leaves 174-176.
178 leaves : ill. ; 30 cm.
Title page, contents and abstract only. The complete thesis in print form is available from the University Library.
Studies the reactivity of metal alkynyl fragments, in particular the formation of compounds containing two or more alkynes, resulting in the preparation of complexes with interesting properties and reactivities.
Thesis (Ph.D.)--Adelaide University, Dept. of Chemistry, 2001

Ph.D.
Compounds, 2,6-bis(3,5-dimethylpyrazol-1-ylmethyl)pyridine (L1) and 2,6-bis(3,5-ditertbutylpyrazol-1-ylmethyl)pyridine (L2) were prepared by phase transfer alkylation of 2,6-bis(bromomethyl)pyridine with two mole equivalents of the appropriate pyrazole. Ligands L1 and L2 reacted with either [PdCl2(NCMe)2] or [PdClMe(COD)] to form mononuclear palladium complexes [(PdCl2(L1)] (1), [(PdClMe(L1)] (2), [(PdCl2(L2)] (3), [(PdClMe(L2)] (4). All new compounds prepared were characterised by a combination of 1H NMR, 13C NMR spectroscopy and microanalyses. The coordination of L2 in a bidentate fashion through the pyridine nitrogen atom and one pyrazolyl nitrogen atom has been confirmed by single crystal X-ray crystallography of complex 3. Reactions of 1, 2 and 3 with the halide abstractor NaBAr4 (Ar = 3,5-(CF3)2C6H3) led to the formation of the stable tridentate cationic species [(PdCl(L1)]BAr4 (5), [(PdMe(L1)]BAr4 (6) and [(PdCl(L2)]BAr4 (7) respectively. Tridentate coordination of L1 and L2 in the cationic complexes has also been confirmed by single X-ray crystallography of complexes 5 and 6. The analogous carbonyl linker cationic species, [Pd{(3,5-Me2pz-CO)2-py}Cl]+ (9) and [Pd{(3,5-tBu2pz-CO)2-py}Cl]+ (10), prepared by halide abstraction from [Pd{(3,5-Me2pz-CO)2-py}Cl2] and [Pd{(3,5-tBu2pz-CO)2-py}Cl2] with NaBAr4, were however less stable. While cationic complexes 5-7 showed indefinite stability in solution, 9 and 10 had t1/2 of 14 and 2 days respectively. Attempts to crystallise 1 and 3 from the mother liquor resulted in the isolation of the salts [PdCl(L1)]2[Pd2Cl6] (11) and [PdCl(L2)]2[Pd2Cl6] (12). Although when complexes 1-4 xviii were reacted with modified methylaluminoxane (MMAO) or NaBAr4, no active catalysts for ethylene oligomerisation or polymerisation were formed, activation with silver triflate (AgOTf) produced active catalysts that oligomerised and polymerised phenylacetylene to a mixture of cis-transoidal and trans-cisoidal polyphenylacetylene. Compounds 2-(3,5-dimethylpyrazol-1-ylmethyl)pyridine (L3) and 2-(3,5-di-tert-butylpyrazol-1-ylmethyl)pyridine (L4) were prepared by phase transfer alkylation of 2-picolylchloride hydrochloride with one mole equivalent of the appropriate pyrazole. Compounds 2-(3,5-bis-trifluoromethyl-pyrazol-1-ylmethyl)-6-(3,5-dimethyl-pyrazol-1-ylmethyl)-pyridine (L5) and 2-(3,5-dimethyl-pyrazol-1-ylmethyl)-6-phenoxymethyl-pyridine (L6) were isolated in good yields by reacting (2-chloromethyl-6-3,5-dimethylpyrazol-1-ylmethyl)pyridine with an equivalent amount of potassium salt of 3,5-bis(trifluoromethyl)pyrazolate and potassium phenolate respectively. L3-L6 react with either [Pd(NCMe)2Cl2] or [PdClMe(COD)] to give mononuclear palladium complexes 13-18 of the general formulae [PdCl2(L)] or [PdClMe(L)] where L = is the bidentate ligands L3, L4, L5 and L6 respectively. Single crystal X-ray crystallography of complexes 13, 15 and 16 has been used to confirm the solid state geometry of the complexes. In attempts to generate active olefin oligomerisation catalysts, the chloromethyl Pd(II) complexes 14 and 16 were reacted with the halide abstractor NaBAr4 in the presence of stabilising solvents (i.e Et2O or NCMe) but no catalytic activities were observed. Decomposition was evident as observed from the deposition of palladium black in experiments using Et2O. In experiments where NCMe was used as the stabilising solvent, the formation of cationic species stabilised by NCMe was evident from 1H NMR analyses. Reaction of complex 14 with NaBAr4 on a preparative scale in a mixture of CH2Cl2 and NCMe solvent gave the cationic complex [[PdMeNCMe(L3)]BAr4 (19) in good yields. Complex 17 reacted with NABAr4 to give tridentate cationic species [[PdMe(L5)]BAr4 (20) which is inactive towards ethylene oligomerisation or polymerisation reactions. The tridentate coordination of L5 in 20 has also been established by single crystal X-ray structure of 20. Catalysts generated from 18 and 19 catalysed ethylene polymerisation at high pressures to branched polyethylene; albeit with very low activity. The Choromethyl palladium complex 14 reacted with sulfur dioxide to form complex 21. The nature of the product has been established by 1H NMR, 13C NMR and mass spectrometry to be an insertion product of SO2 into the Pd-Me bond of 14. Compounds L1-L4 reacted with the nickel salts NiCl2 or NiBr2 in a 1:1 mole ratio to give the nickel complexes [NiCl2(L1)] (22), [NiBr2(L1)] (23), [NiCl2(L2)] (24), and [NiBr2(L2)] (25), [Ni2(μ2-Cl)2Cl2(L3)2] (26), [Ni2(μ2-Br)2Br2(L3)2] (27), [NiCl2(L4)] (29) and [NiBr2(L4)] (30) in good yields. Reaction of L3 with NiBr2 in a 2:1 mole gave the octahedral complex [NiBr2(L4)2] (28) in good yields. Complexes 22-30 were characterised by a combination micro-analyses, mass spectrometry and single crystal X-ray analyses for 27 and 30. No NMR data were acquired because of the paramagnetic nature of the complexes. When complexes 22-30 were activated with EtAlCl2, highly active olefin oligomerisation catalysts were formed. In the ethylene oligomeristion reactions, three oligomers: C11, C14 xx and C16 were identified as the major products. Selectivityof 40% towards α-olefins were generally obtained. In general catalysts that contain the bidentate ligands L3 and L4 were more active than those that contain the tridentate ligands L1 and L2. Dichloride complexes exhibited relatively higher catalytic activities than their dibromide analogues. Turn over numbers (TON) for oligomer formation showed high dependence on ethylene concentration. A Lineweaver-Burk analysis of reactions catalysed by 22 and 26 showed TON saturation of 28 393 kg oligomer/mol Ni.h and 19 000 kg oligomer/mol Ni.h respectively. Catalysts generated from complexes 22-30 also catalysed oligomerisation of the higher olefins, 1-pentene, 1-hexene and 1-heptene and displayed good catalytic activities. Only two products C12 and C15 were obtained in the 1-pentene oligomerisation reactions. The 1-hexene reactions also gave two products, C12 and C18, while 1-heptene oligomerisation reactions gave predominantly C14 oligomers. Five benzoazoles were used to prepare a series of palladium complexes that were invesitigated as Heck coupling catalysts. The compounds 2-pyridin-2-yl-1H-benzoimidazole (L7) and 2-pyridin-2-yl-benzothiazole (L8) were prepared following literature procedures. The new ligands 2-(4-tert-butylpyridin-2-yl)-benzooxazole (L9) and 2-(4-tert-butyl-pyridin-2-yl)-benzothiazole (L10) were prepared by ring closure of aminophenol and aminothiophenol with tert-butyl picolinic acid respectively. The ligand 6-tert-Butyl-2-(4-tert-butyl-pyridin-2-yl)-benzothiazole (L11) was prepared by intramolecular cyclisation under basic conditions is described. Reactions of L7-L11 with either [Pd(NCMe)2Cl2] or [Pd(COD)MeCl] afforded the corresponding mononuclear palladium complexes [PdClMe(L7)] (31), [PdClMe(L8)] (32), [PdCl2(L9)] (33), [PdMeCl(L9)] (34), [PdCl2(L10)] (5), [PdMeCl(L10)] (36) and [PdMeCl(L11)] (37) as xxi confirmed by mass spectrometry and micro-analyses. The palladium complexes 31-37 were efficient Heck coupling catalysts for the reaction of iodobenzene with butylacrylate under mild conditions and showed good stability.

Rubén Vicente and Luis A. López at the University of Oviedo in Spain reported (Angew. Chem. Int. Ed. 2012, 51, 8063) the synthesis of cyclopropyl furan 2 from alkylidene 1 and styrene by way of a zinc carbene intermediate. The same substrate 1 was also converted (Angew. Chem. Int. Ed. 2012, 51, 12128) to furan 3 via catalysis with tetrahydrothiophene in the presence of benzoic acid by J. Stephen Clark at the University of Glasgow. Xue-Long Hou at the Shanghai Institute of Organic Chemistry discovered (Org. Lett. 2012, 14, 5756) that palladacycle 6 catalyzes the conversion of bicyclic alkene 4 and alkynone 5 to furan 7. A silver-mediated C–H/C–H functionalization strategy for the synthesis of furan 9 from alkyne 8 and ethyl acetoacetate was developed (J. Am. Chem. Soc. 2012, 134, 5766) by Aiwen Lei at Wuhan University. Ning Jiao at Peking University and East China Normal University found (Org. Lett. 2012, 14, 4926) that azide 10 and aldehyde 11 could be converted to either pyrrole 12 or 13 with complete regiocontrol by judicious choice of a metal catalyst. Meanwhile, Michael A. Kerr at the University of Western Ontario developed (Angew. Chem. Int. Ed. 2012, 51, 11088) a multicomponent synthesis of pyrrole 16 involving the merger of nitrone 14 and the donor–acceptor cyclopropane 15. The pyrrole 16 was subsequently converted to an intermediate in the synthesis of the cholesterol-lowering drug compound Lipitor. A robust synthesis of the ynone trifluoroboronate 17 was developed (Org. Lett. 2012, 14, 5354) by James D. Kirkham and Joseph P.A. Harrity at the University of Sheffield, which thus allowed for the ready production of trifluoroboronate-substituted pyrazole 18. An alternative pyrazole synthesis via oxidative closure of unsaturated hydrazine 19 to produce 20 was reported (Org. Lett. 2012, 14, 5030) by Yu Rao at Tsinghua University. A unique fluoropyrazole construction was developed (Angew. Chem. Int. Ed. 2012, 51, 12059) by Junji Ichikawa at the University of Tsukuba that involved nucleophilic substitution of two of the fluorides in 21 to form pyrazole 22.

Alkene metathesis has been extended to increasingly complex starting materials and products. Nitriles are good donors to coordinatively-unsaturated transition metal centers, so tend to inhibit the reaction. Ren He of Dalian University of Technology has found (Tetrahedron Lett. 2007, 48, 4203) that inclusion of the loosely-coordinating 2-methyl pyridine in the reaction enables facile cross-coupling with acrylonitrile 2. Although crosscoupling with (Z, Z)-sorbate is not efficient, Dennis P. Curran of the University of Pittsburgh has shown (Organic Lett. 2007, 9, 5) that cross-coupling with (E, Z)-sorbate 5 works well. For large scale work, he has developed a Hoveyda-type catalyst with a perfluoro tail, that is recoverable in 70% recrystallized yield from the reaction mixture. Shigefumi Kuwahara of Tohoku University has reported (Tetrahedron Lett. 2007, 48, 3163) a practical alternative for direct metathesis to deliver (E, E)-dienyl esters. Continuing the investigation of tandem Ru-catalyzed reactions, Marc L. Snapper of Boston College effected (Organic Lett. 2007, 9, 1749) metathesis with methacrolein 8a, then added Ph3P and diazoacetate, to give the diene 11. A range of common Ru catalysts worked well for this transformation. In an alternative approach to trisubstituted alkene construction, Stellios Arseniyadis and Janine Cossy of ESPCI Paris have demonstrated (Organic Lett. 2007, 9, 1695) that inclusion of Cl-catecholborane 14 allows clean cross metathesis with the lactone 13. The construction of tetrasubstituted alkenes has been more challenging. Yann Schrodi of Materia, Inc. (Organic Lett. 2007, 9, 1589) has described a catalyst 17 that is particularly effective. Complex 17 was superior to a catalyst reported (Organic Lett. 2007, 9, 1339) shortly earlier by Robert H. Grubbs of Caltech. Debendra K. Mohapatra of the National Chemical Laboratory, Pune, and Professor Grubbs, in a new approach to macrocyclic stereocontrol, have made (Tetrahedron Lett. 2007, 48, 2621) the remarkable observation that the cyclization of the bis ether 19a gave 20 in a 9:1 E / Z ratio, while cyclization of the diol 9b gave only Z - 21. Oligomer formation can often compete in such medium ring-forming reactions. Deryn E. Fogg of the University of Ottawa has raised (J. Am. Chem. Soc. 2007, 129, 1024) the cautionary (but happy!) observation that while the cyclization, for instance, of 22 proceeded efficiently to give 23, at an intermediate point in the transformation the product was more than half oligomer.

The work is aimed at solving the problem of neutralization of persistent organic pollutants by catalytic methods. In order to identify the relationship between electronic and steric factors of carbenes with catalytic efficiency in the reaction of hydrodehalogenation of haloarenes, the parameters for estimating the ligand influences are proposed (electronic - Ie indices, Ph philicities, ED electron donicities, and EA electron acceptabilities, steric - dimerization energies) using theoretical methods (DFT, B3LYP5, RHF). Synthesis of new heteroaromatic carbenes of the series of sterically shielded 1,3-diarylphenanthro-[9,10-d]imidazol-2-ylidene, 1,3-diaryl-2-methy­lene­phenan­thro-[9,10-d]imidazoline, tetrahydropyrimidin-2-ylidene, 1,3-diaryl­imidazol-2-ylidene, 1,3,4-triaryl-1,2,4-triazol-5-ylidenes, their carbene complexes with palladium iodide, as well as the carbene complex of the superbasic anionic carbene 1,3-bis-(4-oxidophenyl)-imidazol-2-ylidene with nickel(II) ion. 1H and 13C NMR spectroscopy, mass spectrometry and X-ray diffraction study methods were used to establish the structures of the synthesized compounds. A high catalytic effect of a number of sterically shielded carbene complexes (2.4b, 3.5, 4.6a) in the reaction of hydrodehalogenation of p-dichlorobenzene haloarenes with sodium methoxide in isopropanol at 80 °С (TON 98000–110000) was revealed that can be applied to solve the problem of neutralization of persistent organic pollutants. The efficiency of catalysis by sterically open compounds 4.6b and 6.7 appeared to be low (TON 74, 128). The high catalytic effect of sterically shielded compounds is explained by the increased stability of the complexes under the conditions of an alkaline medium caused by metal alkoxides.