A Theoretical Study On Rh(I) Catalyzed Enantioselective Conjugate Addition Reactions of Fluoroalkylated Olefins

Abstract

In this study, quantum mechanical calculations have been performed to elucidate the mechanism and enantioselectivity in rhodium-catalyzed 1,4-conjugate addition reaction of a series of aryl groups to electron-deficient 4,4,4-trifluoro-1-phenyl-2-buten-1-one in the presence of (S)-BINAP. Conjugate addition of unsubstituted, o-CH3, p- and o-Cl substituted phenyl groups were considered to explain steric and electronic effects on the reaction mechanism. The activation energy difference between benzene and o-toluene-substituted systems (8.1 kcal/mol for the R isomer) has shown the impact of steric effects of substituents at the ortho position. The electronic effect of a Cl substituent at the ortho position was demonstrated by an even higher energy barrier (11.9 kcal/mol of energy difference between benzene and o-Cl for R enantiomer). The experimental unreactivity of the o-Cl-substituted system was also confirmed with the calculated high activation energies for both R and S (29.9 and 31.7 kcal/mol for R and S, ...