Catalytic enantioselective 1,3-dipolar cycloaddition of azomethine ylides with vinyl sulfones

A general protocol for the enantioselective catalytic 1,3-dipolar cycloaddition of azomethine ylides with aryl vinyl sultones is described. Nearly complete exo selectivity and enantioselectivities up to 85% ee are attained with Cu(CH3CN)(4)ClO4/Taniaphos as the catalyst system. The resulting enantioenriched 3-sulfonyl cycloadducts are versatile intermediates in the synthesis of 2,5-disubstituted pyrrolidines.