Conjugate Additions of Organocuprates to Cycloalkenone Complexes of the Chiral Rhenium Lewis Acid [(.eta.5-C5H5)Re(NO)(PPh3)]+. Enantioselective Syntheses of 3-Substituted Cycloalkanones Academic Article uri icon

abstract

  • Reactions of organocuprates R2CuLi and cycloalkenone complexes (+)-(R)-[(η5-C5H5)Re(NO)(PPh3) (η1-0=CCH=CHCH2(CH)n)]+ BF4- (n = 2, 1) are conducted in THF or CH2C12 between -15 °C and -116 °C. Workups with aqueous HI give the corresponding 3-substituted cycloalkanones and iodide complex (η5-C5H5)Re(NO)(PPh3) (I). Under optimized conditions, 3-substituted cyclohexanones are obtained in 39—83% yields and 64—85% ee (R = Me, R; n-Bu, R; t-Bu, S; Ph, S or R), and 3-substituted cyclopentanones are obtained in 50-73% yields and 79-93% ee (R = Me, R; Ph, S). Evidence for intermediate enolate complexes is presented, protocols for recycling the chiral rhenium auxiliary are described, and possible mechanisms of 1,4-asymmetric induction are discussed. © 1995, American Chemical Society. All rights reserved.

author list (cited authors)

  • Wang, Y., & Gladysz, J. A.

citation count

  • 20

publication date

  • February 1995