Asymmetric Synthesis of β‐Hydroxy‐β‐trifluoromethylated Ketones via in situ Generation of Trifluoroacetaldehyde and Its Asymmetric Carbon—Carbon Bond Formation Reaction with Chiral Imines in Aqueous Media.

Abstract

Ketones Q 0350Asymmetric Synthesis of β-Hydroxy-β-trifluoromethylated Ketones via in situ Generation of Trifluoroacetaldehyde and Its Asymmetric Carbon-Carbon Bond Formation Reaction with Chiral Imines in Aqueous Media. -Chiral imines (II) and (IV) react with hemiacetal (I) via in situ generation of trifluoroacetaldehyde and simultaneous carbon-carbon bond formation providing a novel asymmetric route to β-hydroxy-β-trifluoromethylated ketones (III) and (V). Although the reaction of (I) with (II) in aqueous media proceeds more slowly than in organic solvents, the enantioselectivities of (III) in aqueous media are slightly better than those in Me-CN and CH2Cl2. The sluggish reaction of (I) with (IV) affords the aldol adduct (V) in low yield, due to the low solubility of the solid chiral imine (IV). Compared to (II), the bulkier naphthyl group in (IV) causes a higher enantioselectivity. -(FUNABIKI*, K.; HASEGAWA, K.; MURASE, Y.; NAGAYA, H.; MATSUI, M.; J. Fluorine Chem. 127 (2006) 4-5, 545-547; Dep. Mater. Sci. Technol., Fac. Eng., Gifu Univ., Yanagido, Gifu 501-11, Japan; Eng.) -H. Hoennerscheid 38-084