Studies On The Synthesis Of Heterocyclic Compounds Containing Nitrogen Atom Induced By Low-valent Titanium Reagent

Low-valent titanium reagent is an important reducing agent, as well as a good catalyst. It shows high reactivity and selectivity and many reactions it caused can be carride out under mild conditions. Our interest is to investigate the intramolecular and the intermolecular reductive reactions of the multi-functional compounds induced by Low-valent titanium reagent to synthesis of a number of heterocyclic compounds containing nitrogen atom.In the second chapter, a novel reductive cyclization of 2-nitrobenzamides with haloketones or keto acids mediated by low-valent titanium reagent has been described. A series of 2,3,3a,4-tetrahydropyrrolo[1,2-a]quinazolin-5(1H)-one and 2,3,3a,4-tetrahydro- pyrrolo[1,2-a]quinazoline-1,5-dione were synthesized in good yields. The structures of the products were determined by IR, 1H NMR, HRMS and X-ray analysis. A possible reaction mechanism was put forward.In the third chapter, a short and reductive coupling reaction of 2-(o-nitrophenyl) imidazole and isocycanates induced by low-valent titanium reagent (TiCl4/Zn) was investigated. A series of imidazo[1,2-c]quinazolin-5(6H)-ones were synthesized in good yields. The structures of the products were determined by IR, 1H NMR analysis. And a possible reaction mechanism was put forward.In the forth chapter, an efficient synthesis of 2-arylquinolin-4(1H)-one derivatives via the reductive cyclization of o-nitrochalcone reduced by low-valent titanium reagent is described. This method has the advantages of short reaction time, high yield and mild reaction conditions. The structures of products were identified by IR and 1HNMR and HRMS spectra. A possible reaction mechanism was put forward.In the fifth chapter, a mild, efficient and novel synthesis of indazoles via cyclization of N-(2-nitrobenzylidene)aniline promoted by low-valent titanium reagent has been described. A series of indazoles were synthesized in good yields. The structures of the products were determined by IR, 1H NMR, 13C NMR, HRMS, MS and X-ray analysis.The remarkable advantages of the above mentioned reactions are mild, neutral, simple operation, good stereoselectivity, good yields and atomic economy.