Copper-catalyzed enantioselective 1,4-conjugate addition of dialkylzinc reagents to alpha,beta- and alpha,beta,gamma,delta-unsaturated ketones

摘要

An enantioselective Cu(II)-catalyzed conjugate addition of dialkylzinc reagents to alpha,beta- or alpha,beta,gamma,delta-unsaturated ketones with chiral cyclohexane-based amidophosphine ligands was developed. With 2 mol% of Cu(OAc)(2)center dot H2O/L5, the conjugate addition of diethylzinc to alpha,beta-unsaturated ketones was achieved in good-to-excellent yields (up to 98%) and high enantioselectivities (up to 92% ee). This catalytic system was shown to be efficient for the 1,4-conjugate addition of Et2Zn to (2E,4E)-1,5-diphenylpenta-2,4-dien-1-one with 85% yield and 90% ee. Moreover, with 1 mol% of Cu(OTf)(2)/L11, the conjugate addition of alpha,beta,gamma,delta-unsaturated ketones was accomplished with 1,4-regioselectivity, good yields (79-86%) and excellent enantioselectivities (up to 97% ee). (C) 2019 Elsevier Ltd. All rights reserved.