Reversal of stereoselectivity in [5+2] pyrone-alkene cycloadditions using a sulfoxide-to-sulfoximine switch. Enantiodivergent synthesis of 8-oxabicyclo[3.2.1]octane systems

[GRAPHICS] Switching from a sulfinyl to a sulfonimidoyl group allows the reversal of t he sense of asymmetric induction in thermal [5C + 2C] intramolecular pyrone -alkene cycloadditions. Removal of the sulfoximine unit from the resulting cycloadducts yields optically active oxabicyclic systems that are enantiome ric to those obtained using the sulfinyl chiral auxiliary.