Bisoxazoline-Catalyzed Asymmetric Nucleophilic Addition of Diethyl Zinc to Fluorinated Alkyl Ketones: Enantiofacial Control by Changing the Bisoxazoline Substituent

Abstract

Bisoxazoline (BOX)-catalyzed asymmetric nucleophilic addition of diethyl zinc to fluorinated alkyl ketones successfully afforded enantioenriched fluorinated alkyl tertiary alcohols. The effect of the size of the substituent on the oxazoline ring on the stereoselectivity of the reaction was investigated. Furthermore, the enantioselectivity could be reversed by altering the BOX bridge structure while retaining the C-4 substituent on the oxazoline ring.

A Copper(I)‐Catalyzed Enantioselective γ‐Boryl Substitution of Trifluoromethyl‐Substituted Alkenes: Synthesis of Enantioenriched γ,γ‐gem‐Difluoroallylboronates

“…[7] Jacobsen has recently reported au nique catalytic method for the asymmetric difluorination of alkenes to generate difluoromethylated stereocenters. [8] Asymmetric copper-catalyzed borylations represent ap owerful tool for the synthesis of optically active organoboron compounds. [9] We and other groups have reported the asymmetric synthesis of allylboron compounds via the asymmetric boryl substitution of allylic compounds (Scheme 1a).…”

Regioselectivity Issues in the Addition of Grignard Reagents to Trifluoromethylated α‐Bromoenones

“…New compounds 3 and 4 were obtained by this procedure. Reduction products 5 and the acetylenic tertiary alcohol 6ac were previously described , …”

“…1‐Phenyl‐3‐(trifluoromethyl)pent‐1‐yn‐3‐ol 6ac : Light yellow oil, 14 mg (12 %). 1 H NMR (CDCl 3 ): 1.19 (t, J = 7.4 Hz, 3H, C 5 H 3 ), 1.93 (q, J = 7.4 Hz, 2H, C 4 H 2 ), 2.62 (s, 1H, OH), 7.28–7.38 (m, 3H, Ph), 7.42–7.50 (m, 2H, Ph).…”

Catalytic Asymmetric Synthesis of α‐Trifluoromethylated Carbinols: A Case Study of Tertiary Propargylic Alcohols

“…For example, Sasaki et al described the use of bis(oxazoline) 32 for the enantioselective addition of Et 2 Zn to trifluoromethyl ketones.A lthough compound 33 was obtained with good selectivity,t he selectivity significantly decreased for the alkynyl substrate (Scheme 21). [41] Recently,t he Hoveyda group introducedaseries of aminophenol catalysts for the catalytic stereoselectivea ddition of organoboron reagents. [42] The features of the catalysis included high catalytic activity (turnover number/frequency) and broad substrate scope.…”