The reaction of trimethylsilyl ethylene oxide with α-sulfonyl anions and α,α-sulfonyl dianions. A method for stereocontrolled synthesis of (E)- and (Z)-allylic alcohols

Article abstract of DOI:10.1016/0022-328X(91)83086-J

Trimethylsilyl ethylene oxide has been shown to react with α-sulfonyl carbanions generated from representative primary alkyl phenyl sulfones to give the corresponding O-trimethylsilyl allylic alcohols, with higher selectivity for (Z)-isomers.The reaction proceeds by attachment of the nucleophile to the α-position of the α,β-epoxyalkylsilane followed by a carbon-to-oxygen shift of the trimethylsilyl group and expulsion of the benzenosulfonyl anion.The reaction of trimethylsilyl ethylene oxide with α,α-sulfonyl dianions followed by partial protonation of the immediate adducts affords O-trimethylsilyl allylic alcohols, mainly (E)-isomers.The reaction of trimethylsilyl ethylene oxide with α-sulfonyl carbanions generated from secondary alkyl phenyl sulfones affords α-trimethylsilyl carbinols as the only or predominant product.In this case the attachment of the nucleophile takes place at the β-position of the α,β-epoxyalkylsilane.The origin of the regio- and stereo-selectivity in reactions of sulfonyl carbanions with α,β-epoxyalkylsilanes is discussed.