Synthesis and reactions of 2-dialkylaminofurans

Abstract

Treatment of tertiary amides of β-aroylpropionic acids with acetic anhydride and perchloric acid gave 2,3-dihydro-2-furylideneammonium salts (5); intermediate acetoxytetrahydrofurylideneammonium perchlorates (4) were isolated in some instances. In the cases of β-m-nitrobenzoylpropionomorpholide and 4-oxovaleromorpholide the reaction stopped at the acetoxytetrahydrofuran stage. The unsaturated iminium salts (5) were deprotonated to yield 2-aryl-5-dialkylaminofurans (6). 2-Morpholino-5-phenylfuran reacted with diazonium fluoroborates to give 3-arylazofurans (9) or their salts; the consitution of the latter is discussed. The hydroperchlorate of 2-morpholino-5-phenylfuran condensed with aromatic aldehydes to form arylidene derivatives (12), which were hydrolysed to the corresponding arylidenebutenolides (13); the condensation product (15) obtained from di-phenylcyclopropenone yielded (2-benzoylethyl)diphenylcyclopropenylium perchlorate. Cycloadditions of maleic anhydride and Nphenylmaleimide to 2-morpholino-5-phenylfuran resulted in rearranged dihydrohydroxy-phthalic acid derivatives. Attempts to prepare primary and secondary aminofurans by the action of acetic anhydride and perchloric acid on the amide and anilide of β-benzoylpropionic acid led, ultimately, to 2-phenyl-Δ¹-pyrrolin-5-one and 1,5-diphenyl-Δ³-pyrrolin-2-one, respectively.