Enantioselective conjugate addition of diethylzinc using catalytic silver(I) diaminocarbenes and Cu(OTf) 2

Abstract

Chiral silver(I) diaminocarbenes act as efficient carbene transfer agents to copper salts. The catalytic species, active in the conjugate addition of diethylzinc to cyclohexenone, is prepared easily at room temperature in various solvents by simply mixing the silver carbene and Cu(OTf) 2. This method avoids the use of strong bases and polar solvents to generate the carbene. The chiral diaminocarbene–copper catalyst, formed in situ, shows a strong accelerating effect and gives enantiomeric excesses up to 23%.