The regioselectivity of copper-catalyzed reactions of allylic chlorides with aryl Grignard reagents was studied by variation of addition time of Grignard reagent, temperature, and amount of catalyst.It was found that slow addition of the Grignard reagent, increased temperature, and increased amount of catalyst favors formation of y-product. Investigation of preformed organocopper species "ArzCuMgBr" and "ArCu(X)MgBr" showed a striking difference in regioselectivity between the two reagents, the latter giving about 90% y-selectivity and the former being nonregioselective. It was found that for "ArCu(X)MgBr" the y-selectivity increased with the electronegativity of the halide X (I Br < Cl).Copper-catalyzed cross-coupling reactions constitute an important class of reactions for the creation of new carbon-carbon b0nds.l Apart from aryl-aryl, vinylvinyl, and aryl-vinyl couplings, copper-catalyzed couplings between an allylic halide or allylic alcohol derivative and an organometallic compound have attracted a lot of attention recently. The principle for these coupling reactions is shown in eq 1 and involves formation of an a X = CI, Br, OCR, S02Ph, OR, OP(O)(OR)a R =alkyl, aryl. vinyl, allyl M = -MgX, -Ti(OR)s, ZnX etc. organocopper intermediate from a transmetalation reaction.2 The most common type of these reactions in organic synthetic applications is the copper-catalyzed Grignard reaction with allylic but recently a number of copper-catalyzed reactions with other organometallics have been rep~rted.',~ An important issue in these reactions is the control of regiochemistry, i.e., whether the leaving group X is displaced a or y by the organometallic reagent. We recently reported a method @ Commercon, A.; Bourgain, M.; Delaumeny, M.; Normant, J. F.; Villieras, J. Tetrahedron Lett. 1975, 3837. (c) Barsantai, P.; Calo, V.; Lopez, L.; Marchese, G.; Naso, F.; Peace, G.
