Unstabilized Azomethine Ylides for the Stereoselective Synthesis of Substituted Piperidines, Tropanes, and Azabicyclo[3.1.0] Systems
作者:Michael A. Ischay、Michael K. Takase、Robert G. Bergman、Jonathan A. Ellman
DOI:10.1021/ja312311k
日期:2013.2.20
azomethine ylides that can (1) be protonated and reduced with high stereoselectivity to give piperidines, (2) participate in [3 + 2] dipolar cycloaddition to give tropanes, and (3) undergo a Nazarov-like 6-π electrocyclization that upon reduction give 2-azabicyclo[3.1.0] systems.
Regioselective synthesis of highly functionalized alkenylboronates by Cu-catalyzed borylation of propargylic silylalkynes
作者:Yeong Eun Kim、DingXi Li、Jaesook Yun
DOI:10.1039/c5dt00144g
日期:——
Highregioselectivity was achieved in the Cu(I)-catalyzed borylation of internal propargylic alkynes with a silyl substituent to afford multifunctionalized alkenylboron compounds. While both the silyl and propargylic substituents are known to act as directing groups, a N-heterocyclic carbene (NHC)–Cu complex furnished β-vinylboronate products (relative to Si) with high selectivity.
Carboxylate-Catalyzed C-Silylation of Terminal Alkynes
作者:Anton Bannykh、Petri M. Pihko
DOI:10.1021/acs.orglett.3c04213
日期:2024.3.15
carboxylate-catalyzed, metal-free C-silylation protocol for terminalalkynes is reported using a quaternary ammonium pivalate as the catalyst and commercially available N,O-bis(silyl)acetamides as silylating agents. The reaction proceeds under mild conditions, tolerates a range of functionalities, and enables concomitant O- or N-silylation of acidic OH or NH groups. A Hammett ρ value of +1.4 ± 0.1 obtained for
Syntheses of proline analogs as potential mechanism-based inhibitors of proline dehydrogenase: 4-methylene-L-, (E)- and (Z)-4-(fluoromethylene)-L-, cis- and trans-5-ethynyl-(.+-.)-, and cis- and trans-5-vinyl-L-proline
作者:Franco Manfre、Jean Marc Kern、Jean Francois Biellmann
DOI:10.1021/jo00033a029
日期:1992.3
Proline dehydrogenase is an enzyme involved in the energetic processes required for flight in certain insects including the tse-tse fly. Proline analogues were designed for the inhibition of this enzyme. For this purpose 4-methylene-L-proline and (E)- and (Z)-4-(fluoromethylene)-L-proline were prepared from trans-4-hydroxyl-L-proline through the following sequence: protection at the nitrogen with a tert-butoxycarbonyl and at the caboxylic acid as methyl ester, oxidation of the hydroxyl group to a ketone, Wittig reaction, and removal of the protecting groups. The cis- and trans-5-ethynyl-(+/-)-proline was prepared from N-(tert-butoxycarbonyl)-3-(trimethylsilyl)-2-propynylamine whose dianion reacted with 1,2-epoxy 4-bromobutane. Cyclization in the presence of trifluoroacetic acid, oxidation of the primary alcohol to acid, and removal of the protecting groups gave cis- and trans-5-ethynyl-(+/-)-proline. Stereoselectivity was observed in the reaction of the dianion of 3-(trimethylsilyl)-2-propynylamine with 1,2-epoxy-4-bromobutane. The cis- and trans-5-vinyl-L-prolines were prepared from N-(methoxycarbonyl)-5-methoxy-L-proline ester by reaction with bis(trimethylsilyl)acetylene in the presence of titanium tetrachloride followed by sequential removal of the protecting groups and by reduction. The cis and trans configuration of the 5-vinyl-L-proline obtained was established by comparison of the NMR spectrum of the trans-N-tosyl-5-vinyl-(+/-)-proline methyl ester with the published spectrum of the trans derivative.
Casara, Patrick; Danzin, Charles; Metcalf, Brian, Journal of the Chemical Society. Perkin transactions I, 1985, p. 2201 - 2208
作者:Casara, Patrick、Danzin, Charles、Metcalf, Brian、Jung, Michel