New entry for synthesis of N-acylhydrazones, pyridazinones, and 1,3,4-oxadiazin-6-ones from α-amino acid esters

Abstract

Versatile electrophiles N-acylhydrazones are synthesized via diazotization, reduction, and acylation of α-amino acid esters. Reduction of diazo esters with L-selectride® or tributylphosphine affords the corresponding hydrazones in good yields. Both reducing agents give anti-hydrazones as the major product although the reactivity of each reductant is slightly different. The resulting hydrazones are acylated to give N-acylhydrazones, which are subjected to further reactions to give 1,3,4-oxadiazin-6-ones that serve as useful synthetic intermediates for the Diels-Alder reaction. © 2007 Pharmaceutical Society of Japan.