Amidophosphane-copper(I)-catalyzed asymmetric conjugate addition of dialkylzinc reagents to racemic 6-substituted cyclohexenones to form 2,5-di- and 2,2,5-trisubstituted cyclohexanones.
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.
Selim
Khalid
K
Graduate School of Pharmaceutical Sciences, Kyoto University, Yoshida, Sakyo-ku, Kyoto, 606-8501, Japan.
Soeta
Takahiro
T
Yamada
Ken-ichi
K
Tomioka
Kiyoshi
K
D000478:Alkylation; D000586:Amination; D002384:Catalysis; D003300:Copper / Q000737:chemistry*; D003512:Cyclohexanones / Q000737:chemistry*; D015394:Molecular Structure; D010720:Phosphines / Q000737:chemistry*; D013237:Stereoisomerism; D013816:Thermodynamics; D017967:Zinc Compounds / Q000737:chemistry*
D003512:Cyclohexanones; D010720:Phosphines; D017967:Zinc Compounds; C036468:cyclohexanone; D003300:Copper; C044646:phosphine