Synthesis Of Bis-(1,4-Dihydropyridine) And Theoretical Studies Of Photocycloadditional Reaction

The 1,4-dihydropyridine is a kind of heterocyclohexadiene derivative with parallel double bonds, which widely spread in natural products and act as backbone unit of many bioactive drugs. To date, lots of studies have been reported in terms of 1,4-dihydropyridines synthesis and their pharmacological activity, but few theoretical studies about their photophysical and photochemical properties have been published. Thus, theoretical studies about bis-1,4-dihydropyridines properties are essential to making their application further in pharmacological area. With these in mind, theoretical studies about bis-1,4-hydropyridine synthesis and their photocycloadditional reaction mechanism were carried out for the purpose of providing theoretical guidance to photochemical reactions of other heterocyclohexadiene derivatives.Synthesis studies of bis-1,4-dihydropyridines. Based on the review of 1,4-dihydropyridine synthesis methods, scheme of preparing bis-1,4-hydropyridines was determined. The synthesis route as following: using amine, aldehyde and 3,3-ethoxypropionate as raw materials and the tetra-butyl ammonium bromide as catalyst, by adopting microwave-assisted synthesis approach in aqueous phase on the foundation of method reported by Sueki to synthesis the titled compounds. The optimized synthesis condition was obtained by investigating the effects of factors, such as reaction temperature, reaction time and microwave power, on yield. Under the condition, 11 bis-1,4-dihydropyridines were prepared and 8 have not been reported amongst them. All structures of these compounds were confirmed by 1H NMR, 13 C NMR, HRMS and IR spectrum.Theoretical studies about photocycloadditional reaction of bis-1,4-dihydropyridines. Structures of bis-1,4-dihydropyridines and the reference 1,4-dihydropyridine within the ground state were optimized under the DFT/B3LYP/6-31G(d,p) calculated level. Subsquently based on the optimized structure, natural bond orbitals, molecular frontier orbitals and corresponding level energy were calculated and analysed; the same calculation about those compounds within the excited state was also carried out under the TDDFT/B3LYP/6-31G(d) calculated level. Feasibility about photocycloaddition reaction of the calculated compounds was discussed. The results showed that symmetry and energy gap of carbon-carbon double bonds orbital in 1,4-dihydropyridine before and after excitating played a determined role in their photocycloaddition reaction. The reaction may proceed when the orbitals were symmetrical and the energy gap less than 0.22049 a.u., otherwise, it can not.