Synthesis of 3-pyrrolin-2-ones by rhodium-catalyzed transannulation of 1-sulfonyl-1,2,3-triazole with ketene silyl acetal.

α-Imino rhodium carbenoids generated from 1-sulfonyl 1,2,3-triazole were applied to the 3 + 2 cycloaddition with ketene silyl acetal, offering a novel and straightforward synthesis of biologically interesting compound 3-pyrrolin-2-one with broad substrate scope.