K₂CO₃-accelerated amidation of carboxylic acids using -oxo ketene-N,S-acetals as amine surrogates

A novel and efficient K2CO3-accelerated amidation of carboxylic acids with alpha-oxo ketene-N,S-acetals as amine surrogates is developed. The amidation of carboxylic acids is achieved in the presence of 10 mol% of K2CO3 using readily available (E)-4-(alkylamino)-4-(ethylthio)but-3-en-2-ones as amine surrogates. The method represents the first example of the synthetic utility of C-N bond cleavage of alpha-oxo ketene-N,S-acetals. A plausible mechanism is proposed on the basis of the detailed studies, in which the base plays the key role during the transformation.