Steroidal sulphur compounds. Part I. Pyrolysis and absolute configuration of steroidal phenyl sulphoxides
作者:D. Neville Jones、M. J. Green
DOI:10.1039/j39670000532
日期:——
eight steroidal sulphoxides has been shown to influence the direction of pyrolytic elimination to give olefins. Consideration of the product ratios and relative stabilities of the transition states lead to the assignment of absoluteconfiguration to the sulphoxides, and provided evidence that the incipient double bonds are well developed in the transition states. Axial sulphoxides eliminate faster
Desulfurization with nickel and cobalt boride: scope, selectivity, stereochemistry, and deuterium-labeling studies
作者:Thomas G. Back、Denise L. Baron、Kexin Yang
DOI:10.1021/jo00061a011
日期:1993.4
A variety of organosulfur compounds containing alkylthio and arylthio groups underwent reductive desulfurization under notably mild conditions when treated with nickel boride, generated in situ from nickel chloride hexahydrate and sodium borohydride in methanol-THF(3:1). Phenyl,chloro, and ester groups are not reduced under these conditions, while iodo, bromo, nitrile, aldehyde, ketone, cyclopropane, and olefinic functions are reduced either completely or partially. Deuterium-labeling studies indicate that the hydrogen that is incorporated into the product originates from both the sodium borohydride and the protic solvent, suggesting the intermediacy of dihydrogen. The epimers 3alpha- and 3beta-(phenylthio)cholestane afforded 3alpha- and 3beta-deuteriocholestane, respectively, demonstrating that the reaction proceeds with retention of configuration. The method may thus be employed for the stereospecific preparation of deuterated products from organosulfur compounds. Arguments are presented in support of a tentative mechanism involving an oxidative addition-reductive elimination sequence via a nickel hydride intermediate.
Electroreductive cleavage of carbon-sulphur bonds in dithioacetals
作者:Nicola Schultz-von Itter、Eberhard Steckhan
DOI:10.1016/s0040-4020(01)81653-7
日期:——
Reaction mechanism studies. 4. The diaxial → diequatorial rearrangement of β-chlorothioethers
作者:J. F. King、K. Abikar、Donna M. Deaken、R. G. Pews
DOI:10.1139/v68-001
日期:1968.1.1
adds diaxially to 5α-cholest-2-ene (1) yielding 2β-chloro-3α-(phenylthio)-5α-cholestane (3). Assuming that the reaction proceeds via the episulfonium ion (2), this allows the inclusion of these species within the scope of the diaxial opening rule. On heating, 3 undergoes rearrangement to 3β-chloro-2α-(phenylthio)-5α-cholestane (4). This reaction is the first instance of a diaxial → diequatorial rearrangement