Synthesis of Furan and Benzene Derivatives Containing Unsaturated Substituents with Electron-Withdrawing Groups, and Analysis of Their Antimicrobial Activity

Furan-2-yl substituted ethenes and conjugated butadienes containing two geminal electron-withdrawing groups, as well as phenylbutadienes with two electron acceptors, were synthesized from the corresponding aldehydes and various β-dicarbonyl compounds via aldol condensation. Reactions of these ethenylfurans and methyl 3-(benzofuran-2-yl)propenoate with arenes in triflic acid (TfOH) yield arylated 2,3-dihydrofurans and 2,3-dihydrobenzofurans, representing a novel synthetic approach to these dihydro derivatives. In contrast, analogous reactions of furanyl- and phenylbutadienes result in carbon–carbon bond cleavage through retro-aldol and related acid-promoted processes. We propose plausible multistep mechanisms and cationic intermediates for these transformations. The synthesized furans and related compounds, at a concentration of 64 μg/mL, exhibit moderate antimicrobial activity against the yeast-like fungus Candida albicans.