Enantioselective Synthesis of Secondary β-Trifluoromethyl Alcohols via Catalytic Asymmetric Reductive Trifluoroalkylation and Diastereoselective Reduction.

Abstract

Fluorinated motifs are frequently encountered in drugs and agrochemicals. Incorporating fluorine-containing motifs in drug candidates for lead optimization in pharmaceutical research and development has emerged as a powerful tool. The construction of molecules that feature a trifluoromethyl (CF3-) group on a stereogenic carbon has accumulated broad research efforts. Unlike its well-explored, biologically active methyl counterpart, asymmetric construction of β-trifluoromethylated alcohols bearing adjacent stereocenters still remains elusive. Through retrosynthetic analysis, we posited that followed by sequential reduction of carbonyl, the initial construction of chiral α-trifluoromethylated ketones could render the desired product in a facile, one-pot fashion. Herein, we developed the first example of nickel-catalyzed asymmtric reductive cross-coupling trifluoroalkylation of acyl chlorides for enantioselective synthesis of diverse α-trifluoromethylated ketones. The one-pot reduction of these α-trifluoromethylated ketones furnished corresponding alcohols bearing β-CF3-substituted stereogenic carbons with excellent diastereoselectivity and complete enantioselective retention. High yields/enantioselectivity, mild conditions, and good functional group compatibility are shown in the system. Utilities of the method are also illustrated by applying asymmetric, late-stage trifluoroalkylation of biologically active complex molecules, revealing tremendous potential for development of CF3-containing chiral drugs.