Stereocontrol in the nucleophilic epoxidation of α-(1-hydroxyalkyl)-α,β-unsaturated sulfones

Article abstract of DOI:10.1016/S0040-4039(00)60042-4

Epoxidation of β-unsubstituted -α-(1-hydroxyalkyl)-α,β-unsaturated sulfones 3 with lithium t-butylperoxide proceeds with high diastereoselectivity to give the syn epoxy alcohols 6. Epoxidation of the triisopropylsilyl ethers 5, however, leads to the anti epoxy ethers 9 with moderate to good selectivity. In contrast to this, epoxidation of (E)-β-phenyl-α-(1-hydroxyalkyl)-α,β-unsaturated sulfones 4 proceeds with high diastereoselectivity to give the anti epoxy alcohols 13. Epoxidation of the corresponding triisopropylsilyl ethers leads to a reversal in diastereofacial selectivity, giving the syn epoxy ethers 14 with moderate selectivity. A rationalisation for these results, based on the principle of 1,3-allylic strain, is proposed.