Bis-sulfonyl ethylene as masked acetylene equivalent in catalytic asymmetric [3+2] cycloaddition of azomethine ylides

Enantioenriched 3-pyrrolines have been synthesized by highly enantioselective Fesulphos-Cu-catalysed 1,3-dipolar cycloaddition of azomethine ylides with trans-1,2-bisphenylsulfonyl ethylene, followed by reductive sulfonyl elimination. High levels of reactivity, exoselectivity, and enantioselectivity have been accomplished for a variety of substituted axomethine ylides. This cycloaddition desulfonylation strategy has been applied as a key step in the enantioselective synthesis of a biologically active C-azanucleoside.