One-pot Synthesis of N-Acyl-N,O-hemiacetals to Develop Novel Difunctionalized N-Acylimines

Abstract

A mild metal-free synthesis of polyfunctionalized N-acyl-N,O-hemiacetals was developed via the nucleophilic addition of unactivated amides to vicinal tricarbonyl compounds. The protocol demonstrated a wide substrate scope, with good isolated yields. The obtained N-acyl-N,O-hemiacetals could be converted into difunctionalized N-acylimines under mild reaction conditions by acetylation of the hydroxy group. In addition, a one-pot synthesis of O-acetyl-N-acyl-N,O-acetals was also achieved. O-Acetylated compounds showed quite good stability and storability even under air. These features represent that O-acetylated acetals serve as excellent precursors for functionalized N-acylimines. The synthetic utility of the generated difunctionalized N-acylimine was successfully demonstrated by examples of the addition reactions using various nucleophiles.