Phase-Transfer Catalyzed Michael Addition Reaction Using a New C2-Symmetric Quaternary Ammonium Salt Derived From l-Proline

Abstract

A new C 2 -symmetric quaternary ammonium salt easily prepared from L-proline, was developed and used as an efficient phase-transfer catalyst (PTC) in Michael addition reaction of various active methylene compounds to aromatic enones. Malonate esters and acetylacetone were reacted smoothly with various a, b-unsaturated ketones in good to excellent yields, the reaction conditions were optimized and the substrate scope was also investigated. Thereby, a practical Michael addition methodology was established under phase-transfer catalytic conditions with many advantages, including easy availability of catalyst, mild reaction conditions, short reaction times, simple workup procedures.