Convenient procedures for the α-metallation of vinylic ethers and thioethers

Abstract

Ethyl vinyl ether H2C=CHOC2H5 and the analogous cyclic vinylic ethers dehydrofuran and 2,3-dihydropyran can be potassiated at −20°C in the α-position with a 1/1/1 molar mixture of BuLi, t-BuOK and TMEDA in hexane. Methyl vinyl sulfide is potassiated very smoothly by a 1/1 molar mixture of BuLi and t-BuOK in THF and hexane at −80°C. Subsequent functionalization (some after exchange of potassium for lithium) provided excellent yields.