Asymmetric conjugate additions to chiral α,β-unsaturated oxazolines with sulfonyl carbanions

Addition of sulfonyl carbanions with or without an electrophilic tether has been shown, under certain conditions, to add to α,β-unsaturated oxazolines in good yields and high deʹs. When 4-bromobutylsulfonyl carbanions are added to unsaturated oxazolines, three contiguous stereocenters are formed and good yields of 1,2,3-substituted cyclohexanes are obtained as a 5:1 mixture of only two diastereomers. The sulfonyl substituent may be reductively cleaved to form selectively 1,2-disubstituted cyclohexanes.