Reactions of alanes and aluminates with tri-substituted epoxides. Development of a stereospecific alkynylation at the more hindered carbon

The addition of 4 equiv of phenyl ethynyl dimethyl alane (formed by treatment of phenyl acetylene with n-BuLi followed by Me2AlCl) to 2,3-epoxy geraniol results in the formation of the C-3 alkynyl addition product and the Yamamoto rearrangement/addition product, in 53 and 18% yield, respectively. Replacing the alane reagent with an aluminate (formed by treatment of phenyl acetylene with n-BuLi followed by Me3Al) and adding BF3·OEt2 result in formation of the C-3 addition product in 73% yield.