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Diprotodecarboxylation reactions of 3,4-dialkoxythiophene-2,5-dicarboxylic acids mediated by AG<inf>2</inf>CO<inf>3</inf> and microwaves

Abstract:

An efficient and rapid method is reported to obtain 3,4-dialkoxythiophenes from 3,4-dialkoxythiophene-2,5-dicarboxylic acids through a diprotodecarboxylation reaction with Ag2CO3/AcOH as a catalytic system and microwave heating in dimethylsulfoxide (DMSO) as solvent. This methodology lets us obtain for the first time good performance with thiophenes bearing strong electron-donating groups such as alkoxides. This methodology eliminates the usage of harmful quinoline as solvent, as well as the long reaction times typically used (12-18 h) to obtain the 3,4-dialkoxythiophenes. The reaction of 7 diacids showed good yields (60-89%) following 20 min of microwave heating in a temperature range of 120-150 °C. [Supplementary materials are available for this article. Go to the publisher's online edition of Synthetic Communications® for the following free supplemental resource(s): Full experimental and spectral details.] © 2014 Copyright Taylor and Francis Group, LLC.