An Efficient Protocol for the Amidation of Carboxylic Acids Promoted by Trimethyl Phosphite and Iodine

A practical, one-pot protocol is described for the conversion of carboxylic acids into amides through carboxyl activation by the reagent combination of trimethyl phosphite and iodine. This method integrates several advantages: (1) it allows amines to be chemoselectively acylated with excellent results in the presence of sulfur and oxygen nucleophiles; (2) the method shows wide generality in respect of solvent, base, and substrate; (3) the reagents used are widely available and much less expensive than common coupling reagents, and (4) the process is remarkably convenient, permitting extraction, recrystallization, and column chromatography as optional work-up procedures. The chemoselectivity and generality of the method, the low cost, and wide availability of reagents combined with the ease of use make it a very favorable process.