2.5- Dimethylpyrrole-2-carboxylate esters

Dimethylpyrrole-2-carboxylate esters having 4-substituents are brominated in excellent yield at the 5-methyl group (Scheme 104) <80JOC1786). Mechanistic studies indicate that this reaction... 

The most convenient laboratory method for the preparation of 2,4-dimethyl-5-carbethoxypyrrole is that given above. A cheaper method of obtaining large quantities consists in the partial hydrolysis of 2,4-dimethyl-3,5-dicarbethoxypyrrole with sulfuric acid, followed by decarboxylation. The ester has been obtained also by the alcoholysis of 5-trichloroaceto-2,4-dimethyl-pyrrole in the presence of sodium ethylate. The free acid has been obtained fronii-[2,4-dimethylpyrrole-5]-2,4-dimethylpyrrole-5-carboxylic acid and from 2,4-dimethylpyrrole-5-aldehyde. ... 

By means of oxidation of the initially formed 3,4-disubstituted 5-bromo-2-bromomethylpyrrole, bromine converted 3,4-disubstituted-2-methylpyr-roles and their 5-carboxylic acids into 5-bromo-5 -bromomethyl-2,2 -dipyrrolylmethanes. Similar reaction with sulfuryl chloride led to the analogous chloro species (77MI2). Whereas treatment of 2-aroyl-l,3-dimethylpyrrole-5-acetic esters with NBS brominated the vacant ring carbon, the related oxalate ester gave the 3-bromomethyl derivative (80JMC98). 

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