Side-chain reactions in π-chromium tricarbonyl-complexed arenes IV. Solvent and deuterium isotope effects in E2 reactions of some 2-phenylethyl and 1-phenyl-2-propyl derivatives

Abstract

The rates and products of elimination with sodium ethoxide in ethanol, and potassium t-butoxide in t-butanol, of chromium tricarbonyl-complexed (2-phenylethyl bromides), (2-phenylethyl tosylates), (1-phenyl-2-propyl bromides), and (1-phenyl-2-propyl tosylates) were determined. Complexation increases the rate of elimination, the size of the effect depending on leaving group, solvent/base system and, to a minor extent structure. The Cr(CO) 3 group increases the olefin percentage when substitution competes with elimination, whereas the relative proportions of the olefin isomers obtained from secondary substrates are practically unchanged whether the ring is complexed or not. Deuterium isotope effects have been measured for the elimination from uncomplexed, complexed and 2-( p-nitrophenyl)ethyl compounds. The magnitude of the isotope effect does not vary appreciably with substituents.