Electrophilic substitution in five-membered heterocyclic systems. Part VI. Kinetics of the bromination of the 2-methoxycarbonyl derivatives of furan, thiophen, and pyrrole in acetic acid solution

Abstract

The kinetics of bromination of the 2-methoxycarbonyl derivatives of thiophen, furan, and pyrrole in acetic acid in the presence of an excess of bromide ions exhibit the same characteristic features as those of the bromination of benzene derivatives. The relative rates for bromination at the α-position are : 2-methoxycarbonylthiophen 1, 2-methoxycarbonylfuran 1·2 × 10², and 2-methoxycarbonylpyrrole 5·9 × 10⁸.