Phenyltrimethylammonium tribromide: A versatile reagent in organic synthesis

Abstract

(A) Oxidation of Secondary Alcohols to the Corresponding Carbonyl Compounds: Sayama et al. showed that PTAB is an available and chemoselective reagent for the oxidation of secondary alcohols and substituted 1,2-diols to the corresponding ketones, 1,2-diketones and α-ketols in the presence of catalytic amounts of SbBr3 or CuBr2 at room temperature.19 The oxidative cleavage of the glycol C-C bond for 1,2-diols was not found. Furthermore, aliphatic primary alcohols were not affected under the same oxidative conditions. (Chemical Equation Presented) (B) Selective Oxidation of Sulfides to Sulfoxides: An efficient procedure for the selective oxidation of various sulfides to the corresponding sulfoxides in aqueous pyridine solution was achieved using PTAB as oxidant.20 This method allowed 18O-labelled sulfoxides to be prepared without loss of isotope enrichment of the used 18O-water. (Chemical Equation Presented) (C) Oxidative Conversion of 3-Alkoxyfurans to 2-Hydroxy-3(2H)- furanones and 2-Hydroxy-2-butene-1,4-diones: PATB can be applied for the oxidative ring opening of 3-alkyoxy-2,5-diphenylfurans to 2-hydroxy-2-butene-1, 4-dions in t-BuOH at room temperature. The transformation of 3-alkyoxy-2,4,5-triphenylfurans to 2-hydroxy-2,4,5-triphenyl-3-(2H)-furanone was also accomplished with PTAB in t-BuOH under the same reaction conditions. 21 (Chemical Equation Presented) (D) One-Pot α- Bromoacetalization of Carbonyl Compounds: A convenient and practical method for the one-pot α-bromoacetalization of carbonyl compound has been developed.22 The reaction was performed in tetrahydrofuran-ethylene glycol (1:1) with 1-2 equivalents of PTAB at room temperature to afford the corresponding α-bromoacetals in good to excellent yields. (Chemical Equation Presented) (E) Aziridination of Alkenes: Dauban and co-workers showed that PATB can catalyze the intramolecular aziridination of N-chloramine salts of ω-unsaturated sulfonamides.23 The aziridination of the alkene can also be carried out employing an understoichiometric amount of chloramines-T trihydrate in the presence of 5 mol% PTAB.24 (Chemical Equation Presented) (F) Coupling Reaction of Carbon Dioxide and Epoxides: A combination of SalenRu(PPh3)225 or metal porphyrin 26 with PTAB has been used as novel and high efficient catalysts for the coupling reaction of carbon dioxide and epoxides to yield the corresponding cyclic carbonates. (Chemical Equation Presented). © Georg Thieme Verlag Stuttgart.