Rh(II)-Catalyzed Transannulation of 1,2,4-Oxadiazole Derivatives with 1‑Sulfonyl-1,2,3-triazoles: Regioselective Synthesis of 5‑Sulfonamidoimidazoles

An
effective method for the synthesis of fully substituted 5-sulfonamidoimidazoles
by Rh­(II)-catalyzed transannulation of 1,2,4-oxadiazole derivatives
with N-sulfonyl-1,2,3-triazoles is reported. The
reaction works well with both aromatic 1,2,4-oxadiazoles and 1,2,4-oxadiazol-5-ones
providing a flexible approach to N-(alkoxy/amino)­carbonyl-
and N-alkyl-substituted imidazoles. Both the disclosed
reactions are completely regioselective and provide the first examples
of a carbenoid-mediated transformation of N,N,O-heterocycles.