Stereochemistry and mechanism of vinyl-migrating [1,2]-Wittig rearrangement of α-lithioalkyl vinyl ethers

Enantiomerically defined alpha-stannylalkyl or alpha-methylbenzyl vinyl ethers, when treated with butyllithium, are shown to undergo the 1,2-vinyl migration to afford the allylic alcohols in almost racemic form in low or high yield, respectively, thereby proposing the radical cleavage-recombination pathway.