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Enantioselective synthesis of chiral heterocycles containing both chroman and pyrazolone derivatives catalysed by a chiral squaramide†
Jun-Hua Li,Da-Ming Du
Organic & Biomolecular Chemistry Pub Date : 04/09/2015 00:00:00 , DOI:10.1039/C4OB02653E
Abstract

An efficient chiral squaramide-catalysed enantioselective Michael addition of pyrazolin-5-ones to 3-nitro-2H-chromenes for the synthesis of chiral heterocyclic systems containing both chroman and pyrazolone derivatives has been developed. This reaction afforded the desired products in high to excellent yields (up to 98%) with high enantioselectivities (up to 96%) and excellent diastereoselectivities (up to 99 : 1) under very low catalyst loading (0.2 mol%). This catalytic asymmetric reaction provides an efficient route toward the synthesis of chiral heterocyclic systems containing both chroman and pyrazolone derivatives, which possess potential pharmaceutical activities.

Graphical abstract: Enantioselective synthesis of chiral heterocycles containing both chroman and pyrazolone derivatives catalysed by a chiral squaramide
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