FULL PAPER * E-mail: hmahdavi@khayam.ut.ac.ir; Tel./Fax: 0098-021-66495291 Received January 24, 2010; revised May 14, 2010; accepted June 3, 2010. Chin. J. Chem. 2010, 28, 2221—2225 © 2010 SIOC, CAS, Shanghai, & WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim 2221 Synthesis and Application of Poly(diallyldimethylammonium tribromide) as a Novel Polymeric Brominating Agent Hossein, Mahdavi* Zahra, Kachoei School of Chemistry, University College of Science, University of Tehran, Tehran, Iran In this study, the synthesis and applications of a new supported tribromide reagent based on poly(diallyldimethylammonium chloride) is reported. This supported tribromide is used in α-bromoacetalization of ketones, bromination of alkenes and regioselective bromination of activated aromatic compounds. This method is mild and no Br 2 and HBr were used. Other advantages of this reagent are stability, high efficiency, simple filtera- bility and reusability. Keywords poly(diallyldimethylammonium tribromide), brominating agent, α-bromoacetalization Introduction Since the first report on the solid-phase peptide syn- thesis by Merrifield, 1 the utilization of insoluble poly- mers as supports in the organic synthesis has received considerable attention. 2 The practical significance of poly(diallyldimethyl- ammonium chloride) has increased rapidly since thirty years ago. This development is caused by a great num- ber of its industrial applications such as processing aids, flocculants, dewatering agents and emulsifiers in pro- cesses of water purifications, paper making, mining and petrol industry, as well as the application as additives. 3 Recently, this polymer was introduced as a new and efficient phase transfer catalyst. 4,5 Generally, bromination is carried out by elemental bromine, but organic ammonium tribromides (OATB) are preferable owing to hazards associated with bromine. The other advantages of organic ammonium tribromides are involving their solid form, high stability, ease of storage, ease of transport, maintenance of desired stoichiometry and mild reaction condition. 6 Hitherto, in the literature several tribromides species have been re- ported i.e, tetramethylammonium tribromide (TMATB), 7 phenyltrimethylammonium tribromide (PTATB), 8 cetyltrimethylammonium tribromide (CetTMATB), 9 tetrabutylammonium tribromide (TBATB), 10 1,8-diazobicyclo[5,4,0]-tetrabutylammo- nium tribromide (DBUHBr 3 ) 11 and pyridinehydrobro- mide perbromide (PyHBr 3 ). 12 However, their prepara- tions involve elemental bromine and in some cases HBr as well. This again causes an environmental concern. In addition, the problems associated with these reagents are the use of expensive organic ammonium cations and in some cases a substantial amount of the organic am- monium tribromides get extracted along with the or- ganic products during work up. Recovery and recycling of expensive organic ammonium cations is also poor after the reaction. α-Bromoacetals are useful synthetic precursors in organic synthesis such as in preparation of α,β-unsaturated ketones, 13 and enol-ethers. 14 One of the effective methods for preparation of α-bromoacetals is one-pot α-bromoacetalization of carbonyl compound with tribromide reagents. 15 Here, to overcome the problems of high cost, recov- ery and recycling of the spent tribromide reagents, we wish to report the synthesis and application of the poly(diallyldimethylammonium tribromide) (PDAD- MATB), as a novel polymeric brominating agent. Experimental Materials and techniques All of the reagents and solvents were purchased from Fluka and Merck and used without further purifi- cations. TGA was recorded on a TA, TGA-Q50. UV-Vis analysis was recorded on Perkin Elmer Lambda 850, UV-Vis spectrometer. IR-spectra were run on a Bruker-Equiuox 55, FTIR Spectrophotometer. NMR spectra were recorded on a Bruker Avance DPX instru- ment (250 MHZ). All products were characterized by comparison of their IR and NMR spectra and physical data with those of the authentic samples. All yields refer to the isolated products. Preparation of poly(diallyldimethylammonium tri- bromide) An aqueous solution of diallyldimethylammonium chloride (2 g, 60 wt%) was purged with nitrogen for 1 h prior to polymerization. The mixture was placed in an