Halogenation of Stilbenes

Since elemental bromine (Br2) is volatile and highly corrosive, special systems, for example, pyridinium tribromide and related compound, are commonly used to generate Br2 in situ [2]. A method for stereoselective bromination of stilbene and chalcone in a water suspension medium using pyridinium tribromide has been reported [2]. Bromination reactions of ( )-stilbene and ( )-chalcone in a water suspension medium by salts 

For the generation of Br2, hydrobromic acid, which is oxidized by hydrogen 

In this reaction, both ( )-stilbene and (Z)-stilbene produce l,2-dibromo-l,2-diphenylethane. However, bromination of the (Z) isomer results in a racemic mixture of DL-stilbene dibromide, while the bromination of an ( ) isomer results in a majority of meso-stilbene dibromide along with small amount of DL-enantiomers. 

A number of methods of bromine production in situ have been reported. A regioselective and stereoselective methoxy-bromination of olefins has been accomplished using LiBr and (diacetoxyiodo)benzene as oxidants [3]. Zinc bromide 

Stilbenes. Applications in Chemistry, Life Sciences and Materials Science. Gertz Likhtenshtein Copyright 2010 WILEY-VCH Veriag GmbH Co. KGaA, Weinheim ISBN 978-3-527-3238S-3 

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