Study On Asymmetric Binary-Acid Catalyzed Nazarov Cyclization/Michael Addition Reaction

Cyclopentenone units are important skeletons for many natural products.As one of the most elegant methods for synthesizing cyclopentenone,the substrate type of the Nazarov reaction is limited to the cis-rotating cyclization ofπelectrons between double bonds.Currently,the synthesis of cyclopentenone containing oxygen atoms through the Nazarov reaction is extremely challenging.We hypothesized that the electrons of the carbonyl group and the double bond can undergo a cis rotational ring closure,thereby designing a conjugated 1,2-diketone substrate,and implemented a series oxa-Nazarov cyclization/Michael addition reaction of conjugated 1,2-diketone compounds through an asymmetric diacid catalytic strategy.The main contents include:（1）The oxa-Nazarov cyclization/Michael addition reaction of conjugated 1,2-diketones was catalyzed by CuBr₂ Lewis acid.The synthesis of oxocyclopentanone compounds with medium to high yield and high enantioselectivity（up to 84%yield,95:5 dr）was carried out in this reaction.（2）The asymmetric binary-acid catalytic strategy of chiral phosphoric acid and FeBr₃ lewis acid was used to achieve the bistereoscopic and enantioselective oxa-Nazarov cyclization/Michael addition reaction of conjugated 1,2-diketones.This reaction efficiently synthesized optically active oxycyclopentenone compounds with good yield and high stereoselectivity（up to 99%yield,95:5 dr,96%ee）.