Ammonium bromides/KF catalyzed trifluoromethylation of carbonyl compounds with (trifluoromethyl)trimethylsilane and its application in the enantioselective trifluoromethylation reaction
has been performed by treatment of Me3SiCF3 under initiation by TBAF, TBAT, TMAF as well as CsF. However, these commercially available fluorides are rather expensive and moisture sensitive. Potassiumfluoride (KF) is an inexpensive and commonly used fluoridesource and can be also used as an initiator for the trifluoromethylation, but the method suffers from the significant limitation that only DMF
Nucleophilic Trifluoromethylation of Carbonyl Compounds and Disulfides with Trifluoromethane and Silicon-Containing Bases
作者:Sylvie Large、Nicolas Roques、Bernard R. Langlois
DOI:10.1021/jo000150s
日期:2000.12.1
Provided that DMF (or another N,N-dialkylformamide) is present in the reaction medium, at least in a catalytic amount, fluoroform trifluoromethylates efficiently carbonyl compounds, even enolizable ones, when opposed to (TMS)(2)N- M+, generated in situ from N(TMS)(3) and M+ F- or RO- Na+ When F- is used ina catalytic amount, silylated alpha-(trifluoromethyl)carbinols are-obtained: in this case, the four-component system HCF3/N(TMS)(3)/catalytic F-/catalytic DMF behaves like the Ruppert's reagent, especially as far as nonenolizable carbonyl compounds are concerned (CF3SiMe3 remains more efficient for enolizable carbonyl compounds). This process involves an adduct between DMF and -CF3 which is the true trifluoromethylating agent. In the same way, fluoroform efficiently trifluoromethylates disulfides and diselenides when deprotonated with a strong base selected from t-BuOK or N(SiMe3)(3)/Me4NF (or TBAT). t-BuOK is more adapted to the trifluoromethylation of aryl disulfides whereas N(SiMe3)(3)/F- is well suited to that of aliphatic disulfides.
Organocatalyzed Trifluoromethylation of Ketones and Sulfonyl Fluorides by Fluoroform under a Superbase System
trifluoromethylation is quite problematic owing to its low acidity and the lability of the naked trifluoromethyl carbanion generated from HCF3. Herein we report the organic‐superbase‐catalyzed trifluoromethylation of ketones and arylsulfonyl fluorides by HCF3. The reactions were carried out by using a newly developed “superbase organocatalyst system” consisting of catalytic amounts of P4‐tBu and N(SiMe3)3
New Stable Reagents for the Nucleophilic Trifluoromethylation. 1. Trifluoromethylation of Carbonyl Compounds with <i>N</i>-Formylmorpholine Derivatives
作者:T. Billard、S. Bruns、B. R. Langlois
DOI:10.1021/ol005987o
日期:2000.7.1
A new stable equivalent of the trifluoromethyl anion has been synthesized from fluoroform. It reacts with nonenolizable carbonyl compounds such as the Ruppert's reagent.