Cocatalysis in phase-transfer catalyzed base induced β-elimination. Part 2: Model studies of dehydrobromination of trans-β-bromostyrene

Abstract

Phase-transfer catalyzed β-elimination of HBr from trans-β-bromostyrene proceeds as a cocatalytic process when cocatalysts of low acidity such as n-butanol and highly concentrated aqueous NaOH at elevated temperatures are used. Without added cocatalyst the reaction is autocatalyzed because the produced phenylacetylene forms lipophilic acetylenide anion acting as a base in the organic phase. Competition between the β-elimination of HBr from trans-β-bromostyrene and the Hofmann degradation of tetrabutylammonium cation as a function of base was studied.