Reaction of carboxylic acids with isocyanides: A mechanistic DFT study

We present a computational investigation of the reaction between isocyanides and carboxylic acids. Our results indicate that this reaction begins with a stereoselective concerted alpha-addition of the acid to the isocyanide, leading exclusively to a Z-acyl imidate. Isomerization to the E isomer and successive rate-limiting 1,3 O -> N acyl migration yields an N-formyl imide. The calculated barriers are in good agreement with the experimental reaction conditions. Our results might provide an explanation for the peculiar reactivity observed when this reaction is carried out in a self-assembled capsule. ((C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008).