E 74% II 50% L6 inone) "(i) MeSSMe (5 equiv), CHzClz, 0 "C, 4 h; (ii) n-Bu3P, 10% aqueous CH,OH, 25 "C, 1 h; (iii) NaH, THF; (iv) MCPBA, CHzC12, 0 "C, 30 min. symmetrical disulfides 1 la/ 12a and 1 lb/ 12b which were separated for characterization purposes. Cleavage of 1 la and 1 lb with tri-n-butylphosphine in aqueous methanol provides o-bromo mercaptans 13a,b in 72% and 78% yield, respectively. Treatment of 13a with sodium hydride in THF at room ...
