Auswahl der wissenschaftlichen Literatur zum Thema „Ring-strained alkenes“
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Zeitschriftenartikel zum Thema "Ring-strained alkenes"
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Jeganmohan, Masilamani, und Pinki Sihag. „Recent Advances in Transition-Metal-Catalyzed C–H Functionalization Reactions Involving Aza/Oxabicyclic Alkenes“. Synthesis 53, Nr. 18 (14.06.2021): 3249–62. http://dx.doi.org/10.1055/a-1528-1711.
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AbstractBicyclic alkenes, including oxa- and azabicyclic alkenes, readily undergo activation with facial selectivity in the presence of transition-metal complexes. This is due to the intrinsic angle strain on the carbon–carbon double bonds in such unsymmetrical bicyclic systems. During the past decades considerable progress has been made in the area of ring opening of bicyclic strained rings by employing the concept of C–H activation. This short review comprehensively compiles the various C–H bond activation assisted reactions of oxa- and azabicyclic alkenes, viz., ring-opening reactions, hydroarylation, and annulation reactions.1 Introduction2 Reactions of Heterobicyclic Ring Systems2.1 Ring-Opening Reactions of Oxa- and Azabenzonorbornadienes2.1.1 Reactions Using 7-Oxabenzonorbornadienes2.1.2 Reactions Using 7-Azabenzonorbornadienes2.2 Hydroarylation Reactions2.3 Annulation Reactions2.4 Other Reactions3 Conclusion
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Nishimura, T., T. Hayashi, E. Tsurumaki, T. Kawamoto und X. X. Guo. „Enantioselective Desymmetrization via Ring Opening of Strained Alkenes“. Synfacts 2008, Nr. 11 (23.10.2008): 1191. http://dx.doi.org/10.1055/s-0028-1083422.
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Sanzone, Jillian R., und K. A. Woerpel. „High Reactivity of Strained Seven-Membered-Ring trans -Alkenes“. Angewandte Chemie International Edition 55, Nr. 2 (27.11.2015): 790–93. http://dx.doi.org/10.1002/anie.201510056.
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Sanzone, Jillian R., und K. A. Woerpel. „High Reactivity of Strained Seven-Membered-Ring trans -Alkenes“. Angewandte Chemie 128, Nr. 2 (27.11.2015): 800–803. http://dx.doi.org/10.1002/ange.201510056.
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Feng, Qiang, Qian Wang und Jieping Zhu. „Oxidative rearrangement of 1,1-disubstituted alkenes to ketones“. Science 379, Nr. 6639 (31.03.2023): 1363–68. http://dx.doi.org/10.1126/science.adg3182.
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The Wacker process, which is widely used to convert monosubstituted alkenes into the corresponding methyl ketones, is thought to proceed through a Pd II /Pd 0 catalytic cycle involving a β-hydride elimination step. This mechanistic scenario is inapplicable to the synthesis of ketones from the 1,1-disubstituted alkenes. Current approaches based on semi -pinacol rearrangement of Pd II intermediates are limited to the ring expansion of highly strained methylene cyclobutane derivatives. Herein, we report a solution to this synthetic challenge by designing a Pd II /Pd IV catalytic cycle incorporating a 1,2-alkyl/Pd IV dyotropic rearrangement as a key step. This reaction, compatible with a broad range of functional groups, is applicable to both linear olefins and methylene cycloalkanes, including macrocycles. Regioselectivity favors the migration of the more substituted carbon, and a strong directing effect of the β-carboxyl group was also observed.
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Shahid, Shereena, Muhammad Faisal, Aamer Saeed, Sarfaraz Ali Ghumro, Hesham R. El-Seedi, Samina Rasheed, Nadir Abbas et al. „A Review on the Scope of TFDO-Mediated Oxidation in Organic Synthesis-- Reactivity and Selectivity“. Current Organic Synthesis 15, Nr. 8 (17.12.2018): 1091–108. http://dx.doi.org/10.2174/1570179415666180831104324.
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Dioxiranes are three-membered strained ring peroxides that are typical archetype examples of electrophilic entities. A dioxirane-based oxidant named 3-methyl(trifluoromethyl)dioxirane (TFDO) is a fluorinated analogue of the extremely valuable oxidant dimethyldioxirane (DMDO). Owing to the strained threemembered ring and presence of electron-withdrawing trifluoromethyl group, TFDO is several times more reactive than DMDO and acts as a significant chemical reagent. Moreover, TFDO exhibits high regio-, chemo- and stereo-selectivity even under unusual reaction conditions, i.e. at pH values close to neutrality and at subambient temperatures. The TFDO transfers an oxygen atom to “unactivated” carbon-hydrogen bonds of alkanes as well as to the double bonds of alkenes and also helps in oxidation of compounds containing heteroatoms having a lone pair of electrons, such as sulfides and amines. TFDO-mediated oxidation is considered to be one of the main procedures in the 21st century for the synthesis of oxygen-containing organic molecules. This review throws light on the applications of TFDO in organic syntheses to provide an insight into the future research and gives a comprehensive summary of the selective functionalization of activated and non-activated organic compounds.
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Ma, Jiajia, Shuming Chen, Peter Bellotti, Tobias Wagener, Constantin Daniliuc, Kendall N. Houk und Frank Glorius. „Facile access to fused 2D/3D rings via intermolecular cascade dearomative [2 + 2] cycloaddition/rearrangement reactions of quinolines with alkenes“. Nature Catalysis 5, Nr. 5 (Mai 2022): 405–13. http://dx.doi.org/10.1038/s41929-022-00784-5.
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AbstractHybrid fused two-dimensional/three-dimensional (2D/3D) rings are important pharmacophores in drugs owing to their unique structural and physicochemical properties. Preparation of these strained ring systems often requires elaborate synthetic effort and exhibits low efficiency, thus representing a limiting factor in drug discovery. Here, we report two types of energy-transfer-mediated cascade dearomative [2 + 2] cycloaddition/rearrangement reactions of quinoline derivatives with alkenes, which provide a straightforward avenue to 2D/3D pyridine-fused 6−5−4−3- and 6−4−6-membered ring systems. Notably, this energy-transfer-mediated strategy features excellent diastereoselectivity that bypasses the general reactivity and selectivity issues of photochemical [2 + 2] cycloaddition of various other aromatics. Tuning the aza-arene substitutions enabled selective diversion of the iridium photocatalysed energy transfer manifold towards either cyclopropanation or cyclobutane-rearrangement products. Density functional theory calculations revealed a cascade energy transfer scenario to be operative.
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Sorensen, T. S., und F. Sun. „cis-2,3-Di-tert-butylcyclopropanones“. Canadian Journal of Chemistry 75, Nr. 7 (01.07.1997): 1030–40. http://dx.doi.org/10.1139/v97-123.
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The preparation of the strained cis-2,3-di-tert-butylcyclopropanone 2 from the acyclic compound, α,α′-dibromodineopentyl ketone 1, using a previously reported methodology, is dramatic evidence of both the existence of oxyallyl intermediates in the mechanism of this reaction, and of the integrity with which oxyallyls ring-close to cyclopropanones by a disrotatory route. Because of the bulky cis substituents, cyclopropanone 2 exhibits a number of unusual spectroscopic features (as compared to the trans isomer 5). With the aid of ab initio calculations on 2 and 5, it can be shown that the C2—C3 bond in 2 interacts with the carbonyl π-orbitals, thus causing the carbonyl oxygen to bend 12° out of the plane; this interaction is absent in 5 and the latter has a planar carbonyl group. As with other cyclopropanones, 2 can be photochemically decarbonylated. This process itself appears to be stereospecific even though highly strained alkenes are produced. Cyclopropanone 2 is thermally rearranged to the trans isomer 5 and the kinetics for this are reported; our favoured mechanism involves oxyallyl intermediates. Other reactions of 2 also appear to proceed through these oxyallyl species; for example, alcohols initially add to 2 to give α-alkoxy ends, solutions of 2 enter into very facile diene cycloadditions, and the dimerization of neat 2 also appears to involve these oxyallyl species. Keywords: cyclopropanones, oxyallyl, stereomutation, stereospecific decarbonylation, nonplanar carbonyl.
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Boutin, Rebecca, Samuel Koh und William Tam. „Recent Advances in Transition Metal-Catalyzed Reactions of Oxabenzonorbornadiene“. Current Organic Synthesis 16, Nr. 4 (04.07.2019): 460–84. http://dx.doi.org/10.2174/1570179416666181122094643.
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Background: Oxabenzonorbornadiene (OBD) is a useful synthetic intermediate capable of undergoing multiple types of transformations due to three key structural features: a free alkene, a bridged oxygen atom, and a highly strained ring system. Most notably, ring-opening reactions of OBD using transition metal catalysts and nucleophiles produce multiple stereocenters in a single step. The resulting dihydronaphthalene framework is found in many natural products, which have been shown to be biologically active. Objective: This review will provide an overview of transition metal-catalyzed reactions from the past couple of years including cobalt, copper, iridium, nickel, palladium and rhodium- catalyzed reactions. In addition, the recent derivatization of OBD to cyclopropanated oxabenzonorbornadiene and its reactivity will be discussed. Conclusion: It can be seen from the review, that the work done on this topic has employed the use of many different transition metal catalysts, with many different nucleophiles, to perform various transformations on the OBD molecule. Additionally, depending on the catalyst and ligand used, the stereo and regioselectivity of the product can be controlled, with proposed mechanisms to support the understanding of such reactions. The use of palladium has also generated a cyclopropanated OBD, with reactivity similar to that of OBD. An additional reactive site exists at the distal cyclopropane carbon, giving rise to three types of ring-opened products.
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Wanapun, D., K. A. Van Gorp, N. J. Mosey, M. A. Kerr und T. K. Woo. „The mechanism of 1,3-dipolar cycloaddition reactions of cyclopropanes and nitrones A theoretical study“. Canadian Journal of Chemistry 83, Nr. 10 (01.10.2005): 1752–67. http://dx.doi.org/10.1139/v05-182.
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The 1,3-dipolar cycloaddition reaction of cyclopropanes and nitrones to give tetrahydro-1,2-oxazine has been studied with density functional theory calculations at the B3LYP/6-31+G(d,p) level of theory. Realistic substituents were modelled including those at the 2-, 3-, 4-, and 6-positions of the final oxazine ring product. The strained σ bond of the cyclopropane was found to play the role of an alkene in a conventional [3+2] dipolar cycloaddition. Two distinct, but similar, reaction mechanisms were found an asymmetric concerted pathway and a stepwise zwitterionic pathway. The reaction barriers of the two pathways were nearly identical, differing by less than ~1 kcal/mol, no matter what the substituents were. The effect of a Lewis acid catalyst was examined and found to have a very large effect on the calculated barriers through coordination to the carbonyl oxygen atoms of the diester substituents on the cyclopropane. The reaction barrier was found to decrease by as much as ~19 kcal/mol when using a BF3 molecule as a model for the Lewis acid catalyst. Solvent effects and the nature of the regiospecificity of the reaction were also examined. Trends in the calculated barriers for the reaction were in good agreement with available trends in the reaction rates measured experimentally. Key words: 1,3-dipolar cycloaddition, cyclopropane, nitrone, tetrahydro-1,2-oxazines, ab initio quantum chemistry, mechanism.
Buchteile zum Thema "Ring-strained alkenes"
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Taber, Douglass. „Alkene Metathesis: Synthesis of Panaxytriol (Lee), Isofagomine (Imahori and Takahata), Elatol (Stoltz), 5-F2t -Isoprostane (Snapper), and Ottelione B (Clive)“. In Organic Synthesis. Oxford University Press, 2011. http://dx.doi.org/10.1093/oso/9780199764549.003.0030.
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Alkene metathesis has been used to prepare more and more challenging natural products. The first and second generation Grubbs catalysts 1 and 2 and the Hoveyda catalyst 3 are the most widely used. Daesung Lee of the University of Illinois at Chicago designed (Organic Lett. 2008, 10, 257) a clever chain-walking cross metathesis, combining 4 and 5 to make 6. The diyne 3 was carried on (3R, 9R, 10R )-Panaxytriol 7. Tatsushi Imahori and Hiroki Takahata of Tohoku Pharmaceutical University found (Tetrahedron Lett. 2008, 49, 265) that of the several derivatives investigated, the unprotected alcohol 8 cyclized most efficiently. Selective cleavage of the monosubstituted alkene followed by hydroboration delivered the alkaloid Isofagomine 10. Brian M. Stoltz of Caltech established (J. Am. Chem. Soc. 2008 , 130 , 810) the absolute configuration of the halogenated chamigrene Elatol 14 using the enantioselective enolate allylation that he had previously devised. A key feature of this synthesis was the stereocontrolled preparation of the cis bromohydrin. Marc L. Snapper of Boston College opened (J. Org. Chem. 2008, 73, 3754) the strained cyclobutene 15 with ethylene to give the diene 16. Remarkably, cross metathesis with 17 delivered 18 with high regioselectivity, setting the stage for the preparation of the 5-F2t - Isoprostane 19. Derrick L. J. Clive of the University of Alberta assembled (J. Org. Chem. 2008, 73, 3078) Ottelione B 26 from the enantiomerically-pure aldehyde 20. Conjugate addition of the Grignard reagent 21 derived from chloroprene gave the kinetic product 22, that was equilibrated to the more stable 23. Addition of vinyl Grignard followed by selective ring-closing metathesis then led to 26.
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Taber, Douglass. „The Hoveyda Synthesis of (-)-Clavirolide C“. In Organic Synthesis. Oxford University Press, 2011. http://dx.doi.org/10.1093/oso/9780199764549.003.0098.
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Conjugate addition-enolate trapping, a strategy originally developed by Gilbert Stork, has become a powerful method for stereocontrolled ring construction. A key step in the synthesis of (-)-Clavirolide C 3 reported (J. Am. Chem. Soc. 2008, 130, 12904) by Amir H. Hoveyda of Boston College occurred early on, with the enantioselective conjugate addition of Me3 Al to 1 to give the silyl enol ether 2. Enantioselective conjugate addition to establish a quaternary center β on a cyclohexanone had been established (OHL August 18, 2008), but not yet on cyclopentanones. Professor Hoveyda found that a modified form of the Ag catalyst that they had published earlie, in combination with the Lewis acidic AlMe3, effected conjugate addition to 1 in 84 % ee. Quenching of the reaction mixture led to the enol silyl ether 2. The assembly of the 11-membered ring of 3 also began with an enantioselective conjugate methylation, of the lactone 4 with Me2Zn, again using a catalyst developed by Professor Hoveyda. Opening of the lactone 5 followed by Swern oxidation gave the Weinreb amide 6, that was homologated and reduced to give 7. Addition of n-BuLi to 2 regenerated the enolate. There were two issues in the addition of that enolate to the aldehyde 7: syn vs. anti stereocontrol, and control of the configuration of the newly formed ternary center on the ring relative to the already-established quaternary center. Inclusion of Et3B in the reaction mixture assured anti aldol formation, but there was only a modest preference for the desired bond formation trans to the slightly more bulky butenyl group, to give 8. Medium rings are more strained than are larger rings. The diene 8 was reluctant to close with the second generation Grubbs catalyst, but the catalyst developed by Professor Hoveyda worked well. The δ-lactone of 3 was then constructed by acylation of 9 with 10 followed by reductive cyclization with SmI2. Conjugate addition to the derived enone 12 on the outside face of the medium ring alkene gave the desired 13 (9:1 dr). This reaction may be proceeding via the s-cis conformer, as the more stable s-trans conformer would have been expected to give the other diastereomer. Dehydration of 13 then delivered (-)-Clavirolide C 3.
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Taber, Douglass F. „The Williams Synthesis of (-)-4-Hydroxydictyolactone“. In Organic Synthesis. Oxford University Press, 2013. http://dx.doi.org/10.1093/oso/9780199965724.003.0083.
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(-)-4-Hydroxydictyolactone 3, representative of the cyclononene xenicanes isolated from the Dictyotacae algae, readily isomerizes thermally to the more stable ( Z )- 6,7-isomer. Attempts to directly form this strained ring system appeared to be fraught with difficulty. David R. Williams of Indiana University envisoned (J. Am. Chem. Soc. 2009, 131, 9038) that use of Suzuki coupling might ameliorate some of the strain, since at the point of commitment to bond formation, the Pd center would be included in the forming ring. This analysis led specifically to the trans ether 1, as cyclization of the trans ether appeared likely to be more facile than would cyclization of the alternative cis diastereomer. The first challenge was the assembly of the array the four contiguous alkylated stereogenic centers of 1. To this end, the Z secondary ester 7 was prepared from the acetonide 4 , available from mannitol, and ( R )-(+)-citronellic acid, prepared by oxidation of the commercial aldehyde. Addition of 7 to LDA led to decomposition, but inverse addition of LDA to a mixture of the ester, TMSCl, and Et3 N smoothly delivered the ketene silyl acetal. On warming, Ireland-Claisen rearrangement of the ketene silyl acetal led to the acid 8 with remarkable diastereocontrol. The last alkylated stereogenic center of 1 was installed by reductive cyclization of the formate ester 9. Again, the cyclization proceeded with remarkable diastererocontrol. Although the intramolecular reaction of in situ prepared allyl metals is well precedented, the addition to a formate ester had not previously been reported. Although 11 appears to be ready for the long-awaited Suzuki coupling, in fact the TIPS protecting group substantially slowed hydroboration. The free alcohol/methyl acetal was the best substrate for hydroboration, but the free alcohol entered into other side reactions. After extensive experimentation, a happy medium was found with the methyl acetal/TBS ether 1. Selenylation of the lactone 12 followed by oxidative elimination of the selenide delivered the expected Z alkene. Removal of the silyl protecting group had to precede introduction of the second alkene, as the product 3 deteriorated rapidly on exposure to the alkaline conditions of TBAF cleavage.
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Taber, Douglass. „The Paquette Synthesis of Fomannosin“. In Organic Synthesis. Oxford University Press, 2011. http://dx.doi.org/10.1093/oso/9780199764549.003.0096.
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The compact sesquiterpene ( + )-fomannosin 3, isolated from the pathogenic fungus Fomes annonsus, presents an interesting set of challenges for the organic synthesis chemist, ranging from the strained cyclobutene to the easily epimerized cyclopentanone. In the synthesis of 3 developed (J. Org. Chem . 2008, 73, 4548) by Leo A. Paquette of Ohio State University, the cyclopentane was constructed by ring-closing metathesis of 1. The real challenge of the synthesis was the enantiospecific preparation of 1 from D-glucose. The starting point for the preparation of 1 was the glucose derivative 4. Selective acetonide hydrolysis followed by oxidative cleavage gave the ester 5, which on base treatment followed by hydrogenation delivered the endo ester 6. Condensation of the enolate of 6 with formaldehyde proceeded with high diastereoselectivity, to give, after protection, the ester 7. Conversion of the ester to the vinyl group, exposure to methanolic acid and ether formation completed the preparation of 9. The construction of the cyclobutane of 1 was effected by an interesting application of the Negishi reagent (Cp2ZrCl2/2 x BuLi). Complexation of Cp2Zr with the alkene followed by elimination generated an allylic organometallic 11, which added to the released aldehyde to give the cyclobutanes 12 and 13 in a 2.4:1 diastereomeric ratio. Homologation of the aldehyde 13 and subsequent oxidation were straightforward, but subsequent methylenation of the hindered carbonyl was not. At last, it was found that Peterson olefination worked well. Metathesis then delivered the cyclopentene 2. The last carbons of the skeleton were added by intramolecular aldol cyclization of the thioester 16. The seemingly simple task of converting the alkene of 17 into a ketone proved challenging. Eventually, dihydroxylation followed by oxidation, and then SmI2 reduction, completed the transformation. This still left the challenge of controlling the cyclopentane stereogenic center. Remarkably, dehydration and epimerization led to (+)-Fomannosin 3 as a single dominant diastereomer.
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Taber, Douglass F. „Functional Group Protection: The Pohl Synthesis of β-1,4-Mannuronate Oligomers“. In Organic Synthesis. Oxford University Press, 2017. http://dx.doi.org/10.1093/oso/9780190646165.003.0015.
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D. Srinivasa Reddy of the National Chemical Laboratory converted (Org. Lett. 2015, 17, 2090) the selenide 1 to the alkene 2 under ozonolysis conditions. Takamitsu Hosoya of the Tokyo Medical and Dental University found (Chem. Commun. 2015, 51, 8745) that even highly strained alkynes such as 4 can be generated from a sulfinyl vinyl triflate 3. An alkyne can be protected as the dicobalt hexacarbonyl complex. Joe B. Gilroy and Mark S. Workentin of the University of Western Ontario found (Chem. Commun. 2015, 51, 6647) that following click chemistry on a non-protected distal alkyne, deprotection of 5 to 6 could be effected by exposure to TMNO. Stefan Bräse of the Karlsruhe Institute of Technology and Irina A. Balova of Saint Petersburg State University showed (J. Org. Chem. 2015, 80, 5546) that the bend of the Co complex of 7 enabled ring-closing metathesis, leading after deprotection to 8. Morten Meldal of the University of Copenhagen devised (Eur. J. Org. Chem. 2015, 1433) 9, the base-labile protected form of the aldehyde 10. Nicholas Gathergood of Dublin City University and Stephen J. Connon of the University of Dublin developed (Eur. J. Org. Chem. 2015, 188) an imidazolium catalyst for the exchange deprotection of 11 to 13, with the inexpensive aldehyde 12 as the acceptor. Peter J. Lindsay-Scott of Eli Lilly demonstrated (Org. Lett. 2015, 17, 476) that on exposure to KF, the isoxazole 14 unraveled to the nitrile 15. Masato Kitamura of Nagoya University observed (Tetrahedron 2015, 71, 6559) that the allyl ester of 16 could be removed to give 17, with the other alkene not affected. Benzyl ethers are among the most common of alcohol protecting groups. Yongxiang Liu and Maosheng Cheng of Shenyang Pharmaceutical University showed (Adv. Synth. Catal. 2015, 357, 1029) that 18 could be converted to 19 simply by exposure to benzyl alcohol in the presence of a gold catalyst. Reko Leino of Åbo Akademi University developed (Synthesis 2015, 47, 1749) an iron catalyst for the reductive benzylation of 20 to 21. Related results (not illustrated) were reported (Org. Lett. 2015, 17, 1778) by Chae S. Yi of Marquette University.
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Taber, Douglass F. „The Nicolaou Synthesis of (+)-Hirsutellone B“. In Organic Synthesis. Oxford University Press, 2013. http://dx.doi.org/10.1093/oso/9780199965724.003.0089.
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(+)-Hirsutellone B 3, isolated from the insect pathogenic fungus Hirsutella nivea BCC 2594, shows good activity (MIC = 0.78 μg/mL) against Mycobacterium tuberculosis. Approaching the synthesis of 3, K. C. Nicolaou of Scripps/La Jolla envisioned and reduced to practice (Angew. Chem. Int. Ed. 2009, 49, 6870) a spectacular tandem intramolecular epoxide opening: internal Diels-Alder cyclization (1 2) that established all three of the carbocyclic rings of 3 with the proper relative and absolute configuration. The construction of 1 began with commercial ( R) -(+)-citronellal 4. Wittig homologation established the ( Z )-iodide 5. Selective ozonolysis followed by condensation with the phosphorane 7 set the stage for Jørgensen-Córdova (Tetrahedron Lett. 2006, 47, 99) epoxidation with H2O2 and a catalytic amount of the Hayashi catalyst 9. Condensation of 10 with the phosphorane 11 followed by Cu-catalyzed coupling of 12 with the organostannane 13 completed the assembly of 1. This approach underscores the strategic advantages of the Jørgensen-Córdova epoxidation over the Sharpless protocol. It is not necessary to reduce the aldehyde to the allyic alcohol, then reoxidize. Furthermore, the Jørgensen-Córdova epoxidation, using catalytic 9, is operationally easier than the Sharpless procedure, which often uses stoichiometric amounts of tartrate ester. The cyclization of 1 proceeded by way of 13, with the newly formed stereogenic center having the diene equatorial on the cyclohexane. Endo cycloaddition catalyzed by the Lewis acid in the solution then gave 2. The facility with which the cyclization of 13 set both the substituents and the stereogenic centers of 2 raises the possibility that the biosynthesis might also follow such an internal [4 + 2] cycloaddition. To complete the synthesis of 3, it was necessary to construct the strained paracyclophane. The authors took advantage of the facile cyclization of the thiolate liberated from 18, then installed the ring-contracted alkene with a Ramburg-Bäcklund rearrangement of 19. They completed the synthesis of (+)-hirsutellone B 3 by exposing the ketone 21 to NH3 in CH3OH/H2O.