Phase transfer catalyzed conjugate addition-initiated ring-closure (CAIRC) reactions with 2-bromo-2-cyclopentenones

Abstract

When 2-bromo-2-cyclopentenone is treated with various carbon nucleophiles containing active methylenes, it undergoes a conjugate addition initiated-ring closure (CAIRC) reaction. This leads to the formation of carboand heterocyclic compounds in a regioselective fashion with good to high yield. Several bases and phase transfer catalysts were investigated. CsF-Si(OEt)4 as base together with benzyldimethyl (2-hydroxyethyl)- ammonium chloride, C6H5CH2N(Cl)(CH3)2CH2CH2OH, as phase transfer catalyst, were found to be mild and efficient reagents for carrying out the synthetic transformation.