Alcohol oxidation reaction with trifluoroethanol

The present procedure is based on the use of fluoroalkyl alcohols as solvents in oxidation reactions. The method is efficient and versatile, and produces disulfides and sulfoxides under mild conditions. These reactions have also been developed using hexafluoroisopropyl alcohol (HFIP) as solvent with a large variety of substrates (alkyl sulfides, alkyl thiols, vinyl sulfides, fiuorinated vinyl sulfides, thioglucosides) by Begue et al."> Replacement of HFIP with trifluoroethanol, a more common and less expensive solvent, also allows the use of mild conditions and affords high yields of disulfides and sulfoxides without contamination. 30% Aqueous hydrogen peroxide is inexpensive and, since water is the sole byproduct, this method is environmentally friendly. 

Until very recently, it was very difficult to prepare carbonyl compounds from alcohols with strong electron-withdrawing groups adjacent to the RCHOH moiety. For instance, 2,2,2-trifluoroethanol is often used as a solvent in oxidation reactions since it has been considered inert to the oxidation. However, the aerobic oxidation of inert perfluoro-substituted alcohols to their corresponding carbonyl derivatives has been recently achieved using Pt(II) complexes with dipyrido[3,2-a 20,30-c]-phenazine ligands (Scheme 10). ° Thus, in the presence of H2SO4 and O2 oxidant, trifluoroethanol was successfully oxidized to trifluoroethyl trifluoracetate with >98% selectivity. 

State. The pre-steady-state changes are consistent with the rapid oxidation of bound alcohol, the concomitant formation of bound NADH, and the perturbation of LMCT bands from the Co(II) center. In the 450 to 700 nm region (Fig. 8A), the time-resolved spectra show that a transient species with a Xmax of 570 nm is formed very rapidly and decays with a rate that is similar to the rate of appearance of enzyme-bound NADH (compare the insets to Figs. 7Aa and 8Aa). It is notable that the d d transitions of the species formed in the very fast initial phase of the benzyl alcohol reaction are highly similar both to those of the stable CoIIHEINAD", trifluoroethanol) complex (Fig. 9) and to the transient species seen in the reduction of benzaldehyde. Below pH 7.5, the amount of intermediate that accumulates decreases. Traces of the intermediate are detectable in the spectra collected at pH 5.6 (Fig. 8C). At pH 4.8, this species could not be detected (Fig. 8B,D). At that pH, the spectral changes indicate... 

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