Electrochemical Investigations of the Fries Rearrangement in Ionic Liquids

Abstract

The Fries rearrangement of phenyl benzoate has been studied in the AlCl 3 : 1-butyl-1-methylpyrrolidinium chloride buffered neutral ionic liquid, giving results similar to those found in the analogous 1-ethyl-3-methylimidazolium chloride system. In the former system, it is possible to observe the reduction of sodium ion, allowing assessment of the buffer level in the system. Further work involves the Fries rearrangement of phenyl benzoate in 1-butyl-1-methylpyrrolidinium triflate ionic liquid. In contrast to the 1-ethyl-3-methylimidazolium tetrafluoroborate system, addition of Lewis acids such as aluminum chloride and boron trifluoride does not result in extensive complexation of the ester in 1-butyl-1-methylpyrrolidinium triflate. An enhancement of the ester reduction processs is, however, observed, indicating that the added acids can interact with the ester to produce an ECE process. These results suggest that the Lewis acids form adducts with the triflate anion, preventing the full activity toward the ester.

Electrochemical Studies of the Fries Rearrangement in Ionic Liquids

“…The observation of reduction processes for both protons and protonated phenyl benzoate is puzzling at this point; however, a rapid equilibrium between these two species may explain this result. Previous work (10) has shown that the addition of triflic acid to phenyl benzoate in the 1-butyl-1-methylpyrrolidinium triflate ( BMPY T f O ) ionic liquid does not result in a potential shift for the phenyl benzoate reduction process. This finding was interpreted as a consequence of the influence of the conjugate base of triflic acid ( triflate anion ) in the ionic liquid, effectively making the triflic acid less acidic in this medium than in EMI BF 4 .…”

“…Recent work in this and other laboratories has involved the study of the Fries rearrangement in ionic liquid systems (3)(4)(5). The reaction has been successfully carried out in the AlCl 3 : 1-ethyl-3-methylimidazolium chloride ( EMIC ) chloroaluminate system (4); however, use of ionic liquids such as EMI BF 4 and BMPY T f O, to which Lewis acids were added, has met with more limited success (5,10). The present work investigates the use of proton acids ( triflic acid, p-toluenesulfonic acid ) in the Fries rearrangement of phenyl benzoate in EMI BF 4 ionic liquid.…”

Electrochemical Investigations of Carbonyl Complexation by Lewis Acids

“…In an ongoing study of the Fries rearrangement, in which phenyl benzoate produces hydroxybenzophenone products, the electrochemical behavior of various Lewis acids ( BF 3 , AlCl 3 , Hf(TfO) 4 ) has been investigated in both ionic liquids (1,2) and acetonitrile (3). The present work begins an effort to understand the formation of Lewis acid complexes with carbonyl compounds in a broader sense, specifically involving aromatic ketones.…”

Electronic Absorption and Voltammetric Analysis of Ni(II) Coordination in the Room Temperature Ionic Liquid: 1-Ethyl-3-Methylimidizolium Chloride/Aluminum Chloride

“…Anhydrous nickel was dried in vacuo for 24 hours. 1-ethyl-3-methylimidizolium chloride (EMIC) was prepared by reaction of 1methylimidazole and 1-chloroethane as described previously (21), and aluminum chloride (Fluka) was purified by closed-tube distillation over aluminum wire (22). The preparation of the samples was done in a dry box under a N 2 atmosphere where the oxygen and water content were kept below 1 ppm.…”