As a continuation of our work on the reductive cleavage of anisole (1) and of dimethoxy- and trimethoxybenzenes (2) under electron-transfer conditions, we have investigated the regioselectivity of cleavage of the carbon-oxygen bonds of phenyl substituted anisoles. The result of the reduction with K metal in THF showed a marked difference in reactivity between the three isomers. Ortho- and para-phenylanisole reacted readily and gave mainly biphenyl (demethoxylation), whereas meta-phenylanisole was less reactive and gave mainly 3-hydroxybiphenyl (demethylation). These findings are at variance with those obtained under the same conditions for the three isomeric dimethoxybenzenes, where demethoxylation was the main reaction of the ortho- and meta-isomers, whereas the para-isomer showed very low reactivity and gave only demethylation. In both systems the results parallel the behaviour of the corresponding radical anions, as evidenced by E.S.R. spectroscopy.
Behaviour of Radical Anions of Methoxy-Substituted Aromatics
Fenude E;
1992
Abstract
As a continuation of our work on the reductive cleavage of anisole (1) and of dimethoxy- and trimethoxybenzenes (2) under electron-transfer conditions, we have investigated the regioselectivity of cleavage of the carbon-oxygen bonds of phenyl substituted anisoles. The result of the reduction with K metal in THF showed a marked difference in reactivity between the three isomers. Ortho- and para-phenylanisole reacted readily and gave mainly biphenyl (demethoxylation), whereas meta-phenylanisole was less reactive and gave mainly 3-hydroxybiphenyl (demethylation). These findings are at variance with those obtained under the same conditions for the three isomeric dimethoxybenzenes, where demethoxylation was the main reaction of the ortho- and meta-isomers, whereas the para-isomer showed very low reactivity and gave only demethylation. In both systems the results parallel the behaviour of the corresponding radical anions, as evidenced by E.S.R. spectroscopy.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.