CHEMOSELECTIVE PROTECTION OF HETEROAROMATIC ALDEHYDES AS IMIDAZOLIDINE DERIVATIVES. PREPARATION OF 5-SUBSTITUTED FURAN- AND TIOPHENE-2-CARBOXALDEHYDES VIA METALLO-IMIDAZOLIDINE INTERMEDIATES

Article abstract of DOI:10.1016/S0040-4020(01)91401-2

Furan-, tiophene- and N-methylpyrrole-2-carboxaldehydes may be transformed into the corresponding N,N'-dimethylimidazolidines in a reaction not requiring acid catalysis.The resulting furan and tiophene (but not N-methylpyrrole) derivatives may be metallated in high yields and the carboxaldehyde functionality regenerated under very mild conditions.Treatment of the aldehydoketone 2-acetyl-5-formylthiophene with N,N'-dimethylethylenediamine gives only the product of reaction at the aldehyde function thus establishing this methodology as a potentially valuable method for the protection of an aldehyde in the presence of a ketone.