ORTHO-CHELATING ARENETHIOLATOCOPPER(I) COMPLEXES AS VERSATILE CATALYSTS IN THE REGIOSELECTIVE CROSS-COUPLING OF ALLYLIC DERIVATIVES WITH NBUMGI - AN EXAMPLE OF REVERSED REACTIVITY OF LEAVING GROUPS

The regioselectivity in the arenethiolatocopper(I)-catalyzed cross-coupling reaction of allylic substrates was studied. It was found that allylic acetates gave highly gamma-selective reactions in Et(2)O at 0 degrees C with slow addition of the Grignard reagent, whereas alpha-selective reactions were obtained in THF at -30 degrees C with East addition of the Grignard reagent. It is proposed that the formation of an intermediate in Et(2)O, in which the allylic acetate coordinates in a bidentate fashion to the arenethiolatocopper(I) catalyst, dramatically increases the reactivity of the leaving group and results in excellent gamma-selectivity. The remarkable observation that an allylic acetate can be made more reactive than an allylic chloride by using the arenethiolatocopper(I) catalyst 1a supports the theory of a bidentate coordination of the substrate to the catalyst through its double bond and acetate oxygen.