Reactivity of alkali and alkaline earth metal tetrafluorobromates towards aromatic compounds and pyridine Vasily I. Sobolev a, *, Victor D. Filimonov b , Roman V. Ostvald a , Vyacheslav B. Radchenko b , Ivan I. Zherin a a Department of Rare, Scattered and Radioactive Element Technology National Research Tomsk Polytechnic University, 634050 Tomsk, Russia b Department of Biotechnology and Organic Chemistry National Research Tomsk Polytechnic University, 634050 Tomsk, Russia A R T I C L E I N F O Article history: Received 11 October 2016 Received in revised form 17 October 2016 Accepted 18 October 2016 Available online 2 November 2016 Keywords: Bromine trifluoride Tetrafluorobromates Bromination Fluorine Arenes A B S T R A C T The bromination activity of tetrafluorobromates of alkali and alkali-earth metals increases in the order KBrF 4 , CsBrF 4 , RbBrF 4 and Ba(BrF 4 ) 2 . The most active tetrafluorobromate—Ba(BrF 4 ) 2 is able to selectively brominate the deactivated aromatic compounds nitrobenzene and 4-nitrotoluene, but not the activated compounds benzene and toluene. In all cases bromination of methyl groups of methylbenzenes does not occur. Ba(BrF 4 ) 2 forms the known complex C 6 H 5 NBrF 3 when reacted with pyridine. Due to dilution by inert BaF 2 , this pyridine-based complex is air stable and can be considered as safer and more convenient reagent in comparison with the original fluorobromates; it can selectively brominate benzene and toluene in contrast with tetrafluorobromates. ã 2016 Elsevier B.V. All rights reserved. 1. Introduction Bromine trifluoride and other bromine fluorides are com- pounds with high fluorinating or brominating ability [1,2]. Particularly Rozen and Lerman showed that BrF 3 can selectively brominate highly deactivated arenes in the presence of bromine; at the same time pure BrF 3 gives complex mixture of products in the cases of benzene and activated arenes [3]. Also BrF 3 is a highly toxic and dangerous compound, with extremely high reactivity [2], especially with organic compounds which lead to explosions. These properties have restrained widespread application of BrF 3 in synthetic chemistry and its usage requires special techniques. Tetrafluorobromates of alkali and alkali-earth metals (TFB), with the common formula M x (BrF 4 ) y , can be considered as BrF 3 - based complexes which are safer and more convenient for use than BrF 3 [4–9]. However, there is no systematic data about the reactivity of TFB towards organic compounds. Recently it was shown that the air-stable complex BrF 3 -KHF could be used in the desulfurizing fluorination of benzylic sulfides and dithioacetals at room temperature in CH 2 Cl 2 solution [6]. Nevertheless, the chemical properties of such compounds in organic reactions are not well-researched and the influence of the M n+ cation is not explored. Herein we describe chemical properties of known fluorobro- mates: KBrF 4 , CsBrF 4 , RbBrF 4 [7,8] and the recently described Ba (BrF 4 ) 2 [9] in reactions with aromatic compounds and pyridine. 2. Results and discussion 2.1. Reactions between KBrF 4 , CsBrF 4 , RbBrF 4 and Ba(BrF 4 ) 2 with nitrobenzene and 4-nitrotoluene Initially the examined TFBs caused strong explosions and decomposition of the initially pure and dry organic substrates to unidentifiable mixtures. However, mild and selective conditions were found in the cases of nitrobenzene 1 and 4-nitrotoluene 2 to give the corresponding m-bromonitroarenes 1a and 2a with good yields. Addition of TFBs to substrates 1, 2 in dry ClF 2 CCCl 2 F (Freon R113) was performed at 25  C with strong stirring before the cooling bath was removed. The reaction mass was stirred at 45  C for 5 h; the gradual gas evolution was observed. The absence of F 2 in the gaseous products was determined by a qualitative test with potassium iodide [10]. Analysis of the reaction mixture was performed using GC–MS and it was found that there were no fluorine-containing organic products. Preparative yields of 1a and 2a (Table 1) in cases of different fluorobromates showed the reactivity order KBrF 4 < RbBrF 4 < CsBrF 4 << Ba(BrF 4 ) 2 . It was also found that strongly deactivated 1,3-dinitrobenzene is inert to Ba(BrF 4 ) 2 . * Corresponding author. E-mail address: vsobolev1989@tpu.ru (V.I. Sobolev). http://dx.doi.org/10.1016/j.jfluchem.2016.10.022 0022-1139/ã 2016 Elsevier B.V. All rights reserved. Journal of Fluorine Chemistry 192 (2016) 120–123 Contents lists available at ScienceDirect Journal of Fluorine Chemistry journa l homepage: www.e lsevier.com/loca te/fluor