International Journal of ChemTech Research CODEN( USA): IJCRGG ISSN : 0974-4290 Vol.1, No.4, pp 1087-1089, Oct-Dec 2009 Microwave assisted oxidation of benzoin on alumina using chromium based oxidants Amit Sahu* 1 , Manish K. Rawal 1 ,Vinod Kumar Sharma 1 and Bharat Parashar 2 1 Microwave Chemistry Laboratory, Department of Chemistry, M. L. Sukhadia University, Udaipur-313001(Raj.) India 2 Geetanjali College of Pharmaceutical Sciences, Udaipur, (Rajasthan), India. *E-mail- amitsahu_1981@yahoo.com ABSTRACT: Chromium based oxidants like pyridinium chlorochromate, benzimidazolium fluorochromate, pyridinium fluorochromate, piperdinium chlorochromate and ammonium chlorochromate supported on alumina has been found to be an effective reagent for the oxidation of benzoin under microwave irradiation. Alumina acts as a catalyst as well as solid support in the reaction and increases the yield of product. The time of the reaction also get reduced considerably. The durability, easy work up and efficiency of chromium based oxidants are considerably increased by using alumina as a solid support. Key Words: Benzoin, Benzil, Chromium based oxidants, Alumina, Microwave. INTRODUCTION α- Diketones are versatile compounds in organic chemistry that can be utilized for the preparation of a variety of molecules. Many of these show a diversity of intresting biological activities (1). Oxidation of α-hydroxy ketone to α-diketone by a wide range of reagent has been reported. The oxidative transformation of benzoins to benzils have been accomplished by a variety of reagents namely nitric acid, Fehling’s solution(2), thallium(III) nitrate(TTN)(3-4), ytterbium(III) nitrate(5), clayfen(6). Chromium (VI) compounds have been reported as versatile oxidants for many type of substrates varying from metal ions to naturally occurring organic compounds. These oxidants have a wide range of applications spamming the synthesis of sulphur *Corres.author: Amit Sahu Research Scholar,Department of Chemistry College of Science M. L. Sukhadia University, Udaipur-313001(Raj.) India E-mail- amitsahu_1981@yahoo.com Mob. No. : (91)9252173650 nanoparticals(7), and the determination of biological oxygen demand in organic polluted water. Cr(VI) chromate or dichromate are highly soluble and are reported to be highly toxic also(8).There researchers are continue for the development of new chromium (VI) reagent for the effective and selective oxidation of organic substrates, under mild condition. Therefore, the search for newer oxidizing agents is of interest to synthetic organic chemist. Many such reagents have been developed recently with some success (9). Some of the important entries in the list of reagents are pyridinium fluorochromate(PFC)(10), Caffinilium chlorochromte (11), quinolinium fluorochromate(12), triphenylemethylphosphonium chlorochromate(13), pyridinium dichromate(14), quinolium chloromate(15), isoquinolinium chlorochromate(16), chromium trioxide 3- 5-Dimethylepyrozole complex CrO 3 3.5-DMP(17), tributyle .ammonium chlorochromate(18),prolinium chlorochromate(19), tripropylammonium fluorochromate(20), Use of supported reagents such as CrO 3 -supported on resin(21), graphite(22), silica gel(23), QFC on alumina(24) etc are also worth mentioning. Alumina is important reagent in industry and in the laboratory and numerous reactions has been carried out