Cyclopropanation/Carboboration Reactions of Enynes with B(C6F5)3
摘要:
Stoichiometric reaction of B(C6F5)(3) with 1,6-enynes is shown to proceed via initial cyclopropanation and formal 1,1-carboboration. Depending on the substitution on the alkene moiety, subsequent ring-opening of the cyclopropane affords either cyclopentane or cydohexane derivatives in which the C6F5 and B(C6F5)(2) adopt a 1,4-positioning. Mechanistically, this transformation involves pi-activation of the alkyne moiety, which triggers cydopropanation, followed by carboboration. Both the cydopropanation and subsequent ring-opening are shown to be stereospecific. Both cyclopropanation and 1,4-carboborated products were employed as Lewis acid components in frustrated Lewis pair activation of H-2 and CO2.
Bismuth(III) Chloride Catalyzed Cycloisomerization of Enynes
作者:Zezhou Wang、Shiyue Fang
DOI:10.1002/ejoc.200900819
日期:2009.11
Several simple bismuth(III) salts were screened for the suitability to catalyze the cycloisomerization of enynes. Among them, BiCl3 gave the best results. Under the optimized reaction conditions, eight substrates were studied, and acceptable to excellent isolated yields were obtained. Consistent with data in the literature, electron-deficient alkynes were found to be better substrates for the reaction