Abstract
The asymmetric conjugate addition of dialkylzinc reagents to racemic 6-substituted cyclohexenones under the catalysis of chiral amidophosphane-copper(I) complexes gave a mixture of nearly equal amounts of the corresponding trans- and cis-disubstituted cyclohexanones with extremely high catalyst-controlled enantioselectivity. Epimerization with 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) led to the conversion of these mixtures into the thermodynamically more stable trans-2,5-disubstituted cyclohexanone as the major product with up to 96% ee in up to 96% yield. The regio- and stereoselective alkylation of the disubstituted cyclohexanone products via the thermodynamically favored enolate gave 2,2,5-trisubstituted cyclohexanones with a quaternary asymmetric carbon atom in good yield.
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