Boron Trifluoride-Mediated Alkylation of Diphenylphosphine with <i>tert</i>-Alkyl Fluoride
作者:Koji Hirano、Hideki Yorimitsu、Koichiro Oshima
DOI:10.1021/ol048069p
日期:2004.12.1
stoichiometric amount of boron trifluoride etherate yields the corresponding tert-alkyldiphenylphosphine despite the coexistence of the strong Lewis acid and the highly coordinating phosphine. Use of diphenyl(trimethylsilyl)phosphine as a nucleophile makes the reaction catalytic in boron trifluoride.
Alkylation of silyl enolates with tert-alkyl or allylic fluorides proceeds smoothly in the presence of a catalytic amount of borontrifluoride to afford the corresponding carbonyl compounds. Allylation and reduction of alkylfluorides with allylsilane and hydrosilane, respectively, occur under BF3 catalysis.
Generation of allylic and benzylic organolithium compounds by fluorine–lithium exchange: reaction with electrophiles
作者:David Guijarro、Miguel Yus
DOI:10.1016/s0022-328x(00)00770-1
日期:2001.4
lithiation methodology to allylic and benzylic fluorides 1 led to the corresponding allylic and benzylic organolithium reagents, which, in the presence of different electrophiles (Barbier-type reaction conditions), afforded the expected products 2 in moderate yields. The procedure was useful for the transformation of primary, secondary and tertiary benzylic fluorides into the corresponding lithium
A new, mild method to prepare alpha-trifluoromethylated amides bearing an additional trans-configured double bond in gamma-position is described. Treatment at room temperature of fluorinated and non-fluorinated allylic alcohols 1 and 2 with the 1,1,3,3,3-pentafluoropropene-diethylamine adduct (PFPDEA) in the presence of triethylamine as base gave the products of [3,3]-sigmatropic Eschenmoser-Claisen-type rearrangements with good yields and excellent diastereoselectivity due to chair-like conformations of transition states. Starting with enantiomerically enriched allylic alcohols chirality transfer from carbon 3 of the allylic system to carbon 2 of the final alpha-trifluoromethyl carboxamides was observed. This methodology was applied to both simple and more complex, including terpenic, allylic alcohols and might be developed to an alternative strategy to the well-known electrophilic alpha-trifluoromethylation of carbonyl compounds. (C) 2012 Elsevier B.V. All rights reserved.