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Synlett 2009(8): 1351-1352  
DOI: 10.1055/s-0029-1216645
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© Georg Thieme Verlag Stuttgart ˙ New York

Pyridinium Hydrobromide Perbromide: A Versatile Reagent in Organic Synthesis

Shu-Hong Yang
The College of Chemistry & Material Science, Hebei Normal University, 050016 Shijiazhuang, P. R. of China
e-Mail: yang_shuhong@126.com;
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Publikationsdatum:
07. Mai 2009 (online)

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Introduction

Pyridinium hydrobromide perbromide (PHPB) has been extensively used in organic synthesis as a selective brominating reagent for alkenes, [¹-5] alkanes, [6] arenes, [7] ketones, [7] [8] anilines, [9] aromatic ethers, [¹0] N-heterocycles, [¹¹] and oxidi­zing reagents. [¹²] [¹³] PHPB forms red prismatic crystals and its melting point is at 134 ˚C. Further, it is easy to handle, stable and environmentally safe. [¹4] PHPB has been used for regioselective heterocyclization of ortho-cyclohexenyl phenols [¹5] and ipsobromodeformylation in o-hydroxy and o-methoxy substituted aromatic aldehydes. [¹6] It was also found to be a useful catalyst for the chemoselective deprotection of primary TBS and TES ethers, [¹7] hydrolysis of thioacetals, [¹8] and hydroamination of activated styrenes. [¹9]

Pyridinium hydrobromide perbromide is commercially available, but it can be readily prepared by adding one mole of bromine to one mole of pyridine in 48% hydrobromic acid solution. [¹4]