Reduction of monothioacetals with SmI2: application to [2,3]-Wittig rearrangement

Simple reduction of O,S-acetals with SmI2 yielding ethers with selective liberation of the sulfenyl group can be accomplished using benzene–HMPA with t-BuOH. When O,S-acetals possess an O-allyl group, the [2,3]-Wittig rearrangement yielding homoallyl alcohols follows the elimination of a sulfenyl group. For chemoselective elimination of an alkoxy group to give sulfides, MeOTf serves as a moderately effective additive.