THE EFFECT OF POLYMER-SUPPORTED REAGENT STRUCTURE ON BROMINATION OF ORGANIC-MOLECULES

Crosslinked poly(styrene-co-4-vinylpyridine) reacted with hydrogen bromide or various alkyl bromides to pyridinium salts, which were further converted with chlorine to polymer supported reagents (1) containing up to 34% of chlorine, while substantial loss of bromide was observed during chlorination, debromination being diminished with increase in the length of the alkyl chain in the pyridinium salt. Polymeric reagents (1) converted 1,1-diphenylethene to 2-bromo-1-chloro-1,1- -diphenytelhane and 2-bromo-1,1-diphenylethene, the structure of 1 influencing both the reactivity and the ratio of the addition to elimination process. The brominating capacity of reagents 1 was determined with an excess of 1,1-diphenylethene and varied, according to the structure of 1, in the range of 0.4 - 1.4 mmol per gram of polymeric reagent.Bromochlorination of various cis and trans-phenylakenes with polymeric reagent 1d proceeded anti stereospecifically and followed the Markovnikov type of regioselectivity, the only exception being (Z)-1-phenylpropene, where 9% of regioisomer was formed, while vicinal bromide chlorides were accompanied with up to 7% of vicinal dibromides. The rate of bromination in isopropylbenzene depended on the structure of the reagent 1, as well as the para/ortho regiospecifity, being in the range of 3.6 - 4.0. © 1990.