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Download fileNucleophilic Trifluoromethylation of Carbonyl Compounds and Disulfides with Trifluoromethane and Silicon-Containing Bases
journal contribution
posted on 2000-12-07, 00:00 authored by Sylvie Large, Nicolas Roques, Bernard R. LangloisProvided 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)2N- M+, generated in situ from N(TMS)3 and M+ F- or RO- Na+.
When F- is used in a catalytic amount, silylated α-(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.
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Keywords
TMSDMFtrifluoromethylating agentfluoroform trifluoromethylatesBuOKenolizable onesCarbonyl Compoundsaliphatic disulfidestrifluoromethylates disulfidesCF 3 SiMe 3enolizable carbonyl compoundsRONucleophilic TrifluoromethylationCF 3HCF4 NFcarbonyl compoundsaryl disulfidesnonenolizable carbonyl compoundsTBAT2 Nreaction medium