A Cobalt Mediated Nitrene Transfer aza-Wittig Cascade Reaction To Access 1,3,4-Oxadiazole Scaffolds

• DOI: 10.1021/acs.orglett.3c00959
• Publication Date: 2023-05-24T17:19:52Z
• Authors: Daniël S. Verdoorn; Prabhat Ranjan; Tim de Reuver; Elwin Janssen; Christophe M. L. ...; Jordy M. Saya; Bert U. W. Maes; Romano V. A. Orru
• Keywords: Chemistry; Molecular Structure; Carboxylic Acids; Cobalt; Imines

A cobalt(II) mediated three-component synthesis of 5-substituted-N-sulfonyl-1,3,4-oxadiazol-2(3H)-imines using sulfonyl azides, N-isocyaniminotriphenylphosphorane (NIITP), and carboxylic acids has been developed. This one-pot tandem reaction starts with a nitrene transfer to NIITP, followed by addition of the carboxylic acid to the in situ formed carbodiimide and subsequent intramolecular aza-Wittig reaction. Both the steric constraints of carboxylic acid and the stoichiometry of the employed cobalt salt determine the selectivity toward the two products, i.e. 5-substituted-N-sulfonyl-1,3,4-oxadiazol-2(3H)-imine versus 5-substituted-4-tosyl-2,4-dihydro-3H-1,2,4-triazol-3-one.