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Amidation of Carboxylic Acid with Amines by K60 Silica
J. W. Comerford, J. H. Clark*, D. J. Macquarrie, S. W. Breeden
University of York, UK
22 June 2009 (online)
The amidation of carboxylic acids with amines catalyzed by a thermally activated silica gel was described. The reaction of 4-phenylbutyric acid with aniline was performed with a variety of catalysts in refluxing toluene for 24 hours (eq. 1 and Table). The highest catalytic activity was seen with a thermally activated Kieselgel 60 (K60; activation temp. 700 ˚C; average pore size 6 nm) that gave 4,N-diphenylbutyramide in 55% conversion. K60 (20-50 wt%) was applied to the amidation of various combinations of carboxylic acids 1 with amines 2 under similar conditions to afford the corresponding amides 3 in 38-98% conversion (eq. 2; 12 examples).