REGIOCONTROL IN COPPER-CATALYZED CROSS-COUPLING OF ALLYLIC CHLORIDES WITH ARYL GRIGNARD-REAGENTS

The regioselectivity of copper-catalyzed reactions of allylic chloride s with aryl Grignard reagents was studied by variation of addition tim e of Grignard reagent, temperature, and amount of catalyst. It was fou nd that slow addition of the Grignard reagent, increased temperature, and increased amount of catalyst favors formation of gamma-product. In vestigation of preformed organocopper species ''Ar2CuMgBr'' and ''ArCu (X)MgBr'' showed a striking difference in regioselectivity between the two reagents, the latter giving about 90% gamma-selectivity and the f ormer being nonregioselective. It was found that for ''ArCu(X)MgBr'' t he gamma-selectivity increased with the electronegativity of the halid e X(I < Br < Cl).