Synthesis Of Dihydropyrimidinones And Photochemical Studies Of 5-Methylbicyclo(1.1.1)Pentane Derivatives

In 1893, Biginelli had reported the synthesis of dihydropyrimidinones (DHPMs) by one-pot condensation of benzaldehyde, urea and ethyl acetoacetate under strongly acidic conditions for the first time. Due to the wide therapeutical and pharmacological properties of DHPMs, the symthesis of DHPMs had attracted considerable attentions.In the first place, Lewis acid surfactant-combined catalysts (LASCs) had successfully applied to the Biginelli reaction for the first time. We found that 10% Ce(C12H25SO3)3 can efficiently catalyze the Biginelli reaction of benzaldehyde, ethyl acetoacetate and urea in ethanol with 93% yield. Additionally, we could also synthesize many dihydropyrimidinones derivatives by varying substrates. Partillarly, the tolerance to EDG, EWG, sterically hindered substituents, and simple recyclability without losing catalytic activity making the catalyst practical for futher application.In the second place, the p-orbital overlap controlled enantioselectivity of solid-state Norrish typeⅡphotoreaction was also investigated. Irradiation of 5-methyl bicyclo[1.1.1]- pentanyl ketone by UV in solid state or in acetonitrile solution afforded the Norrish/Yang photocyclized compound as the sole product. These results were supported by X-ray single crystal structure. Further more, by means of ionic interaction, the reactant with a carboxylic acid substituent could react with an optically pure ammonium ion (the ionic chiral auxiliary). Solid-state asymmetric photochemical studies, using ionic chiral auxiliary technique, give us 60% enantioselectivity.