Structure and Additive-free Transamidation of Planar N-Cyano Amides

Abstract

Although transamidation of amides generally requires metals, additives, or harsh conditions, we present here a facile transamidation of Ncyano amides with various amines at ambient temperature without any additive. N-cyano amides preferred the trans conformation and have a reduced double bond character revealed by crystal analysis. The DFT study indicates that the transamidation reaction proceeds through the direct attack of amine on the amide carbonyl since the LUMO (or LUMO+1) is located at the carbonyl moiety.

Structures and Reactivities of N-Alkenyl-Substituted Anilides: The “Magic” Methyl Effect on Alkene

“…In the case of the secondary anilides, such as acetanilide ( 1 ), they generally favor the trans conformer, whereas N -methylated tertiary amides tend to adopt the cis conformer . This cis conformational preference of tertiary amides is mainly explained by the electronic repulsion between carbonyl and twisted phenyl group, caused by the “magic methyl” effect on amide nitrogen, in the trans conformer. , N -Ethynyl and cyano acetanilides ( 3a and 3b ) favor the trans conformer to avoid triple bond-carbonyl electrostatic repulsion, whereas their N -vinyl surrogates favor the cis conformation to avoid alkene-carbonyl repulsion through an s-trans N–C­(=C) rotamer . However, the effects of substitution on the alkene moiety remain to be explored in detail.…”