CsF-Catalyzed Nucleophilic Trifluoromethylation of <i>trans</i>-Enones with Trimethyl(trifluoromethyl)silane: A Facile Synthesis of <i>trans</i>-α-Trifluoromethyl Allylic Alcohols

Abstract

Reactions of trans-enones, R−CC−COR' (R = Ph, Me, R' = Ph, Me, Et, CF3) (1a−e), with TMS-CF3 in the presence of catalytic amounts of cesium fluoride (CsF) in ethylene glycol dimethyl ether led to the formation of the corresponding trans-α-trifluoromethyl silyl ethers, R−CC−C(OSiMe3)(CF3)R' (R = Ph, Me, R' = Ph, Me, Et, CF3) (2a−e), in essentially quantitative yield. On hydrolysis with aqueous HCl, the corresponding trans-α-trifluoromethyl allylic alcohols, R−CC−C(OH)(CF3)R' (R = Ph, Me, CF3) (3a−e), were formed in >90% isolated yield. Under similar reaction conditions, 2-cyclohexen-1-one (1f) also gave trifluoromethyl allylic alcohols (3f) in 92% yield. The intermediates (2a−f) and products (3a−f) are liquids and were characterized by IR, 1H, 19F and 13C NMR, MS, and high-resolution mass spectroscopy (HRMS).