Cu(ii)-catalyzed asymmetric Mukaiyama–Michael reaction: concise synthesis of cyclohexadiene analogues

Abstract

Herein, an asymmetric Mukaiyama–Michael reaction catalyzed by chiral copper complexes was reported. Using 0.5 mol% of Cu(OTf)₂–imidazolidine–pyrroloimidazolone pyridine as a catalyst, a Mukaiyama–Michael reaction between silyl enol ethers and β,γ-unsaturated α-keto esters was achieved, affording chiral 1,5-dicarbonyl compounds in good yields (up to 94% yield) and high enantioselectivities (96–99% ee). β,γ-Unsaturated α-ketoamides and isatins were also compatible with this catalytic system. Using but-2-ene-1,4-dicarbonate as an allyl substrate, an efficient Pd-catalyzed allylic reaction of 1,5-dicarbonyl compounds was reported for the preparation of chiral cyclohexadiene products in excellent stereoselectivities.