Difluoromethylation of some C–H acids with chlorodifluoromethane under conditions of phase transfer catalysis (PTC)
摘要:
Selected C-H acids react with difluorocarbene generated from chlorodifluoromethane with concentrated aqueous solution of sodium hydroxide, and a catalyst, benzyltriethylammonium chloride (TEBAC) in benzene or THF affording C-difluoromethyl substituted derivatives. This process is restricted to C-H acids of pK(a) congruent to 16.3-19.1. The observed facts are rationalized. (C) 2009 Elsevier B.V. All rights reserved.
highly carbon‐selective difluoromethylation of soft carbon nucleophiles including β‐ketoesters, malonates, oxindoles, benzofuranones and ketenesilylacetals with a difluoromethylated sulfonium ylide under mild conditions was described. Mechanistic studies suggest that these difluoromethylating reactions proceed via a difluorocarbene pathway.
Utilization of fluoroform for difluoromethylation in continuous flow: a concise synthesis of α-difluoromethyl-amino acids
作者:Manuel Köckinger、Tanja Ciaglia、Michael Bersier、Paul Hanselmann、Bernhard Gutmann、C. Oliver Kappe
DOI:10.1039/c7gc02913f
日期:——
be considered as an ideal reagent for difluoromethylation reactions. However, due to the low reactivity of fluoroform, only very few applications have been reported so far. Herein we report a continuous flow difluoromethylation protocol on sp3 carbons employing fluoroform as a reagent. The protocol is applicable for the direct Cα-difluoromethylation of protected α-amino acids, and enables a highly atom
Double agent: The direct α‐difluoromethylation of lithiumenolates using an umpolung form of fluoroform as a difluoromethyl carbocation equivalent leads to an all‐carbon quaternary center. Late transition metals are not necessary and the reaction involves activation of inert CF bonds with subsequent CCbond formation.