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

Chiral silver(I) diaminocarbenes act as efficient carbene transfer agents t o copper salts. The catalytic species, active in the conjugate addition of diethylzinc to cyclohexenone, is prepared easily at room temperature in var ious solvents by simply mixing the silver carbene and Cu(OTf)(2). This meth od avoids the use of strong bases and polar solvents to generate the carben e. The chiral diaminocarbene-copper catalyst, formed in situ, shows a stron g accelerating effect and gives enantiomeric excesses up to 23%. (C) 2001 E lsevier Science Ltd. All rights reserved.