The generation and chemistry of dianions derived from furancarboxylic acids

Abstract

Methods for the generation of the dianionic species lithium 5-lithiofuran-2-carboxylate (5) and lithium 2-lithiofuran-3-carboxylate (21) from furan-2-and furan-3-carboxylic acids respectively are described. The reactions of (5) and (21) with a range of electrophiles have been examined; in general these are very efficient with aldehydes and ketones but not as satisfactory with alkyl halides and epoxides. The dianions do not couple with allylic or benzylic halides, nor with nitriles or orthoesters. The generation of lithium-5-lithio-3-methylfuran-2-carboxylate (15) from 3-methylfuran-2-carboxylic acid is also described; the chemistry of (15) is very similar to (5) derived from furan-2-carboxylic acid.