Esters of furan-, thiophen-, and N-methylpyrrole-2-carboxylic acids. Bromination of methyl furan-2-carboxylate, furan-2-carbaldehyde, and thiophen-2-carbaldehyde in the presence of aluminium chloride
- 1 January 1973
- journal article
- research article
- Published by Royal Society of Chemistry (RSC) in Journal of the Chemical Society, Perkin Transactions 1
- p. 1766-1773
- https://doi.org/10.1039/p19730001766
Abstract
Convenient routes from readily available starting materials to furan- and thiophen-2-carboxylic acids with substituents (mainly halogen atoms) at various positions are described. A series of esters (methyl, ethyl, t-butyl, and 17-oxo-5α-androstan-3β-yl) have been prepared from these acids and from the unsubstituted heterocyclic 2-carb-oxylic acids. Methyl furan-2-carboxylate reacts with bromine in the presence of aluminium chloride to give the 4,5-dibromo-ester. The presence of 1,2-dichloroethane changes the course of the reaction, the product then being the 4-bromo-5-chloro-ester. Furan-2-carbaldehyde shows the opposite behaviour, giving as the main products the 4-bromo-5-chloro-aldehyde in the absence of a solvent and the 4,5-dibromoaldehyde when 1,2-dichloroethane is present. Careful control of conditions is necessary in the preparation of 4-bromothiophen-2-carbaldehyde from thiophen-2-carbaldehyde, bromine, and aluminium chloride.Keywords
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