Improved Synthesis Of Dibenzalacetone Derivatives Under Ultrasound Irradiation

During the last decades, ultrasound has been increasingly used in organic synthesis.Compared with traditional methods, ultrasound irradiation can give higher yield, shorterreaction time and mild condition. Some recently applications of ultrasound in the organicreactions such as oxidation reactions, reduction reactions, condensation reactions, additionreactions and substitution reaction, are summarized.Synthesis of1,5-diaryl-1,4-pentadien-3-one via the condensation of aromatic aldehydesand acetone (or benzalacetone) was carried out in53%~96%yields catalyzed by KOHaqueous solution in ethanol at r.t. for standing20~50min. This method provides severaladvantages such as short reaction times, high yields, simple operation and mild conditions.Synthesis of1,5-diaryl-1,4-pentadien-3-one amidinohydrazone hydrochloride via thecondensation of1,5-diaryl-1,4-pentadien-3-one and aminoguanidine hydrochloride catalyzedby hydrochloric acid under ultrasound irradiation. While catalyzed byp-dodecylbenzenesulfonic acid (DBSA),1,5-diaryl-1,4-pentadien-3-one amidinohydrazonehydrochloride was carried out in84-94%yield at25-27oC within2-3h under ultrasoundirradiation in water.Synthesis of2-cinnamoyl-1-styryl-3,4-diarylcyclopentanol via cyclodimerization of1,5-diaryl-1,4-pentadien-3-one mediated by zinc was carried out in good yields at roomtemperature in NH4Cl (aq.)/THF under ultrasound irradiation. In comparison withconventional methods, the main advantages of these present procedures are shorter reactiontimes and higher yields.