Michael Addition of Various Nitrogen and Oxygen Nucleophiles to 1,1-Diethoxybut-3-yn-2-one

Abstract

1,1-Diethoxybut-3-yn-2-one, a conjugated terminal acetylenic ketone, reacts with nitrogen and oxygen nucleophiles and gives Michael adducts, in most cases in good to excellent yield. In almost every case the predominant reaction is monoaddition, which leads to formation of the corresponding β-substituted α,β-unsaturated ketones in a stereospecific fashion. The stereochemistry depends on the nature of the nucleophile, the general pattern being that ammonia and primary amines give Z-alkenones, whereas secondary amines and alcohols afford E-alkenones. Triethylamine does not furnish a Michael addition product, but catalyzes a trimerization that leads to formation of a 6H-1,3-dioxine derivative. When bis-nucleophiles, for instance hydrazine and hydroxylamine, are used, the Michael-addition products are unstable and undergo secondary reactions to form heterocyclic compounds, which are isolated in excellent yields.