A Highly Potential Analogue of Jacobsen Catalyst with In-built Phase Transfer Capability in Enantioselective Epoxidation of Nonfunctionalized Alkenes

Abstract

A new analogue of Jacobsen MnIII SALEN epoxidation catalysts having in-built phase transfer capability by means of introducing tertiary amino alkyl groups at the 5,5′-position of the Salen ligand were used as catalysts for the liquid-phase enantioselective epoxidation of 2,2-dimethyl-6-cyano chromene, indene, and styrene in the presence of O-coordinating axial bases with NaOCl as an oxidant under biphasic reaction conditions. Excellent conversions were obtained with catalyst loading in the range 0.4–2.0 mol% in all alkenes, but high chiral induction (EEs>99%) was obtained only in the case of 2,2-dimethyl-6-cyano chromene. The enhanced activity of these complexes is attributed to the presence of t-alkyl amines in the Salen ligand, imparting in-built phase transfer capability to the catalyst.