Wiley InterScience Backfile Collection 1832-2000
Chemistry and Pharmacology
The regioselectivity in the arenethiolatocopper(I)-catalyzed crosscoupling reaction of allylic substrates was studied. It was found that allylic acetates gave highly γ-selective reactions in Et2O at 0°C with slow addition of the Grignard reagent, whereas α-selective reactions were obtained in THF at -30°C with fast addition of the Grignard reagent. It is proposed that the formation of an intermediate in Et2O, in which the allylic acetate coordinates in a bidentate fashion the arenethiolatocopper(I) catalyst, dramatically increases the reactivity of the leaving group and results in excellent γ-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.
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