A straightforward synthesis of methylenebisamides from amides and DMSO with a substoichiometric amount of (COCl)2

The preparation of methylenebisamides has been achieved by the reaction of amides with dimethyl sulfoxide (DMSO) in the presence of a substoichiometric amount of (COCl)2 in toluene at reflux. Various amides, including aliphatic and aryl amides, lactams, and carbamates, can be converted to the corresponding methylenebisamides in good to high yields. It is proposed that HCHO generated in situ from the decomposition of DMSO catalyzed by (COCl)2 reacts with amides to afford the bisamides, which is promoted by proton produced in the decomposition of DMSO without requiring any additional catalysts. The reactions with DMSO‑d6 also give the corresponding methylenebisamides-d2 in high yields.