Studies On The Aromatization Of DHPMs And Synthesis Of Quinoline Compounds

This dissertation mainly consists of two parts. In the first part, we studied the application of visible light photocatalysis in aromatization of 3,4-dihydropyrimidin-2(1H)-ones. In the second part, a high efficient approach for synthesis of 2-substituted quinoline derivatives was achieved by employing Hantzsch ester 1,4-dihydropyridines as a biomimetic reducing agent. The details were obtained as following:1. The functionalized pyrimidin-2(1H)-one moiety occurs in many biologically active and medicinally significant structures. With visible-light irradiation (λ> 400 nm) of Re(1)(Phen)(CO)3Br, a high-yield photocatalytic conversion from 3,4-dihydropyrimidin-2(1H)-ones to pyrimidin-2(1H)-ones is achieved in an aqueous MeCN solution containing CCl4 and K2CO3. Control experiments demonstrated that light, catalyst and CCl4 are essential for formation of corresponding products. The present method provides a facile protocol for synthesis of functionalized pyrimidin-2(1H)-ones utilizing visible-light photocatalysis.2. The reductive cyclization of o-nitrocinnamoyl compounds is an important access to form 2-substituted quinolines. However, this procedure is somewhat difficult because of the lack of selectivity in the reduction of a nitro group in the presence of olefinic and carbonyl substituents. By employing Hantzsch ester 1,4-dihydropyridines as a biomimetic reducing agent in the presence of catalytic Pd/C, the transformation of o-nitrocinnamoyl compounds to substituted quinolines has been accomplished in high to excellent yields in refluxing acetic acid. The high selectivity of the reduction indicates that HEH is not only the reductant of the reaction but also the modifier for the Pd surface. The preferential absorption of HEH hinders absorption and the selective hydrogenation of the less-reactive moiety, thereby leading to the predominant hydrogenation of the nitro groups.