Copper-Catalyzed Olefination of 4-CF3-Substituted Cyclohexadienones Using Sulfonylmethyl Isocyanides: An Electrostatic Repulsion-Controlled Regioselectivity Switch Strategy

초록

A Cu(OTf)2-catalyzed olefination of cyclohexadienones was developed using sulfonylmethyl isocyanides. A CF3 moiety at the 4-position of cyclohexadienones was shown to exert a pronounced electrostatic repulsion effect to give the olefination products via a preferential [3+2] cycloaddition with the ketone moiety followed by a facile fragmentation of transient oxazoline intermediates. The current Cu(II)-catalyzed olefination of 4-CF3-substituted cyclohexadienones demonstrates the reaction dichotomy involving a CF3-controlled 1,2-addition over a Van Leusen 1,4-addition pathway through the electrostatic repulsion effect.

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