Synthesis of N-acylamidines via rhodium-catalyzed reaction of nitrosobenzene derivatives with N-sulfonyl-1,2,3-triazoles.

α-Imino rhodium carbene, readily generated from N-sulfonyl-1,2,3-triazole, underwent cycloaddition and subsequent rearrangement with a nitrosobenzene derivative to afford N-acylamidine. The unprecedented C-C bond cleavage of α-imino carbene was facilitated by the weakness of the N-O bond.