The Characteristics Of Aldol Condensation Between Cyclopentanone And Aldehydes

The characteristics of aldol condensation between cycloalkanones and n-heptanal, aromatic benzaldehydes over various acids and bases catalysts were studied. It was found that base catalysts promoted activity of a-hydrogen atom in the molecular structure of cyclopentanone towards a cross-condensation reaction. While Bronsted and Lewis acids made a protonated carbonyl group in the molecular structures of cyclopentanone and benzaldehydes to enhance the positive charge density of the carbonyl carbon towards a self-condensation reaction.The aldol condensations using inorganic base, sodium hydroxide, were effectively discussed towards a high selection.2-Hepteneyl cyclopentanone in63.4%of yield was obtained by using cyclopentanone/n-heptanal of1.3:1molar ratio under mild conditions in the promotion of phase transfer catalyst. While2-benzylidene cyclopentanone in66.8%of yield was achieved for cyclopentanone/benzaldehyde of1.8:1molar ratio.Utilization of dimethylamine in aldol condensation appear of efficacy. The yield of2-hepteneyl cyclopentanone reached65.5%by the use of cyclopentanone/n-heptanal of1.2:1molar ratio. Likewise, piperidine could catalyze aldol condensation between cyclopentanone and benzaldehyde. The yield of2-benzylidene cyclopentanone was73.1%by using cyclopentanone/benzaldehyde of2:1molar ratio. However a self-redox reaction for benzaldehyde could exist in strong alkaline conditions.Aluminium oxide supported sodium hydroxide was favored to the crossed aldol condensation in good selectivity.2-Hepteneyl cyclopentanone of67.2%was yielded for cyclopentanone/n-heptanal of3:1molar ratio, and80.1%2-benzylidene cyclopentanone was obtained for cyclopentanone/benzaldehyde of2:1molar ratio.Various aromatic aldehydes,3-chlorobenzaldehyde,3-nitrobenzaldehyde, and4-methylbenzaldehyde, were chosen to react with cyclopantanone. Some inorganic bases such as sodium hydroxide and aluminium oxide supported sodium hydroxide facilitated the aromatic aldehydes with electron-withdrawing groups. Moreover, organic piperidine base was more powerful for4-methylbenzaldehyde of electron-donating group. The synthesized compounds were characterized by1H NMR...