Promotional effect of ionic liquids in electrophilic fluorination of methylated uracils

Abstract

A novel efficient protocol has been developed for fluorination of methylated uracils involving a stoichiometric amount of ionic liquid (IL) in alcohols. The fluorination of 6-methyluracil and 1,3,6trimethyluracil has been carried out using the electrophilic fluorinating reagent Selectfluor™ (F-TEDA-BF 4 ) in MeOH and EtOH solvents with the formation of 5-fluoro-6-methyluracil, 5-fluoro-1,3,6trimethyluracil as well as a-fluoromethoxyand a-fluoroethoxy ethers of difluorodihydrouracils as the main products. The use of a stoichiometric amount of ionic liquid as an additive results in acceleration of the reaction. It has been found that the effect of the anion of the IL on the rate of the reaction is more pronounced compared to that of the cation, the effectiveness of the anions decreasing in the following order: [HSO 4 À ] > [OTf À ] $ [NTf 2 À ] > [BF 4 À ] > [PF 6 À ]. The influence of metal carbonates on the yields of fluorouracils has also been evaluated. a N.N. Vorozhtsov Novosibirsk Institute of Organic Chemistry, Siberian Branch of the Russian Academy of Sciences, Academician Lavrent'ev Ave., 9, Novosibirsk, 630090, Russian Federation.

Promotional effect of ionic liquids in electrophilic fluorination of phenols

“…A mixture of phenol (20 mg), F-TEDA-BF 4 (1.1 equivalents), IL (0-15 equivalents) and the organic solvent (5 mL) was stirred for 5 h at various temperatures under an argon atmosphere (Tables 1-5). The mixture was evaporated at a reduced pressure and analysed by 1 H, 19 F NMR as solution in CDCl 3 or CDCl 3 -DMSO-d 6 . Cl 2 CHCHCl 2 and PhCF 3 were used as internal standards for peak integration.…”

“…Recently, we have studied promotional effect of ionic liquids in electrophilic fluorination of methylated uracils with Selectfluor TM in alcohols. 19 The use of a stoichiometric amount of ionic liquid as an additive results in acceleration of the reaction. As a part of our program aimed at exploring the potential use of a stoichiometric amount of ionic liquid we have tried to use similar catalytic strategy for fluorination of phenol, 1-naphthol and resorcinol in various solvents.…”