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

A cobalt(II) mediated three-component synthesis of 5-substituted--sulfonyl-1,3,4-oxadiazol-2(3)-imines using sulfonyl azides, -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 formed carbodiimide and subsequent intramolecular -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.