Novel Method of Synthesis of Quaternary Ammonium Tribromides and Investigation of Catalytic Role of Benzyltrimethylammonium Tribromide in Oxidation of Alcohols to Carbonyl Compounds

Abstract

Stable crystalline organic quaternary ammonium tribromides (QATBs) have been easily synthesized by the oxidation of the corresponding organic ammonium bromides (QABs) with ammonium persulfate. The reactions have been performed under solvent-free conditions in the presence of sulfuric acid and silica as supporting agent. Two equivalents of potassium bromide have been used as the source of additional bromides for quantitative conversion of QABs to QATBs. Ammonium persulfate, a cheap and readily available oxidant, carries out the bromide oxidation to tribromide very effectively under solvent-free conditions. The synthesized QATBs have been shown to catalyze the oxidation of alcohols to carbonyl compounds with hydrogen peroxide as oxidant in good yields under mild reaction conditions.

GRAPHICAL ABSTRACT

Keywords:

• Ammonium persulfate
• green synthesis
• organic ammonium tribromides
• oxidation

ACKNOWLEDGMENT

S. S. Dhar acknowledges the Department of Science and Technology (DST), New Delhi, for funding the work through DST-SERC Fast Track Project No. SR/FTP/CS-100/2007.

Notes

^a Reaction conditions: Substrate (1 mmol), BTMATB (10 mol%), aqueous hydrogen peroxide (2 mmol, 30 wt%), acetonitrile (5 mL) at 60 °C.

^b Isolated yields.

^c Experiment carried out using (50 mol%) of BTMATB in the presence of hydrogen peroxide (2 mmol, 30 wt%) at 60 °C.