Novel Metal- and Mineral-Acid–Free Synthesis of Organic Ammonium Tribromides and Application of Ethylenephenanthrolium Bistribromide for Bromination of Active Methylene Group of 1,3-Diketones and β-Ketoesters

Abstract

A novel procedure for the preparation of organic ammonium tribromides (OATBs) is described from their corresponding bromides. Quaternary ammonium bromides (QABs) and a N,N′-heterocyclic dibromide are efficiently oxidized to their corresponding monotribromides and bistribromide by m-chloroperbenzoic acid (MCPBA) in the presence of 2 and 4 equiv of KBr, respectively. The reactions are carried out in an aqueous medium without the use of any mineral acid or metal catalyst/promoters. A variety of tribromides are synthesized in very good yields including a hitherto unknown reagent, 1,10-(ethane-1, 2-diyl)phenanthrolinediium bistribromide (EPDBT). EPDBT is investigated as brominating agent and found to be highly effective for selective bromination of active methylene groups of a variety of 1,3-diketones and β-ketoesters.

GRAPHICAL ABSTRACT

Keywords:

• Bistribromide
• bromination
• 1,3-diketones
• β-ketoesters
• MCPBA
• metal-free

ACKNOWLEDGMENTS

The authors are thankful to the Sophisticated Analytical Instrument Facility, IIT Madras and IIT Bombay, for providing the spectral analyses of the compounds.

SUPPORTING INFORMATION

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