Ring opening of disubstituted epoxides linked to a secondary oxygen group with an organocopper reagent

Coupling reactions of epoxide linked to a secondary oxygen group with Gilman reagents were examined. The regiochemical direction depended on whether there is TMS or MOM as a protective group of the secondary alcohol. anti-Epoxy alcohol 6 tended to react with Me2CuLi at the C4 position to generate 1,2-diol 22 as a major component. Epoxide 7 linked to a trimethylsilyloxy group displayed selective formation of 1,3-diol 18. On the other hand, the reactions of syn-epoxy alcohol 12 and the corresponding TMS ether 13 resulted in the selective formation of 1,2-diol 25.