Amidic resonance not a barrier for transamidation of N-pivaloyl activated amides: catalyst, base and additive free conditions

Abstract

Transamidation of twistless (twist angle (τ) = 4.54°) and resonance stabilized N-pivaloyl activated amides is demonstrated in the absence of a catalyst, base and additive. Furthermore, C–N (1.374 Å) and CO (1.222 Å) bond lengths indicate the existence of amidic resonance; yet, transamidation is achieved at room temperature with alkyl amines in a short reaction time (0.5–2 h) with 60–97% yield. Amines bearing protic hydroxy and carboxylic acid groups were tolerated under the reaction conditions. Thus, our findings imply that N-pivaloyl-activated planar and resonance-stabilized amides are sufficiently reactive for nucleophilic addition.