Hydrocyanation. Part X. Cleavage of epoxides with hydrogen cyanide and triethylaluminium and with diethylaluminium cyanide

Abstract

Steroidal epoxides are smoothly cleaved by hydrogen cyanide–triethylaluminium and by diethylaluminium cyanide under mild conditions to give the corresponding trans-diaxial β-cyanohydrins, except for the 5β, 10β-epoxide (XXVIb) which gives the cis-β-cyanohydrin (XXVIII) as well as the major, trans-diaxial product (XXVIIb). The compounds examined included the 5α,6α-, 5β,6β-, 9α,11α-, 9β,11β-, 16α,17α-, 2α,3α-, 3α,4α-, 11α,12α-, 5α,10α-, and 5β,10β-epoxides. The successful cleavage of the 9α,11α-epoxides (VIII) to give the 9α-hydroxy-11β-cyano-steroid (IX) is significant in view of the fact that 9α,11α-epoxides are known to resist cleavage by lithium aluminium hydride or hydrogen halides. β-Cyanohydrins are also obtained from the corresponding β-bromohydrins by treatment with hydrogen cyanide and triethylaluminium.