Unprecedented 1,3-tert-butyl migration via the C-N single bond scission of isonitrile: an expedient metal-free route to N-sulfonyl amidines.

An unprecedented 1,3-migration of the tert-butyl group was observed while reacting tert-butyl isonitrile with N,N-dibromoaryl sulfonamides and nitrile. The reaction involves the simultaneous C–N single bond scission of isonitrile and the migration of the tert-alkyl group to the adjacent unsaturated nitrogen centre of the nitrile precursor, which eventually results in the formation of N-sulfonyl amidine. This method constitutes a new route for sulfonyl amidine, which does not rely on transition metals. The protocol exhibits a significant advantage in terms of substrate scope and additionally offers an easy synthesis route to guanidine molecules.