Transition Metal-catalyzed Synthesis Of Heterocyclic Compounds

Nitrogen and oxygen heterocyclic compounds are the most important heterocyclic molecules, besides most of them have biological activity and pharmacological activity. As the intermediates of medicine, pesticide, natural medicine, dye and other chemical products, nitrogen and oxygen heterocyclic compounds are playing an important role in our life. Therefore, it is necessory for us to synthesize them. So far, although there are so many methods synthesizing nitrogen and oxygen heterocyclic compounds, it is needed to find or develop new , effective, environment-friendly, mild reactional conditions and easy-operational methods. While, metal-catalyzed organic reaction is the effcientest methord to synthesize nitrogen and oxygen heterocyclic compounds. Iron and indium salts are usually used as the catalyst of the organic reactions, because they are cheap and low-toxic. The thesis which used cheap metal salts as the catalysts and explored the synthesis of the nitrogen and oxygen heterocyclic compounds ,are discussed as follows:(1) In this paper, An efficient synthetic strategy toward the cyclic addition of 2,2'-dihydroxybiphenyl to terminal alkynes has been developed using Lewis acid TiCl₄ as catalyst. The reactions generated dibenzo[d,f][1,3]dioxepines derivatives in good yields with excellent regio-selectivity in the presence of catalytic amount of TiCl₄ under mild reaction conditions.(2) In this paper, A simple, environmental-friendly, and practical method for synthesis of benzodiazepine derivatives through the reaction of substituted o-phenylenediamines with alkyl propiolates has been reported. The reaction generated the 1,5-benzodiazepines in presence of catalytic amount of In(OTf)₃ under solvent-free reaction conditions in good to excellent yields.(3) In this paper, A novel Fe(II)/diaryl prolinol catalyzed asymmetric 1,3-dipolar cycloaddition of azomethine ylides with alkenes has been developed. In the presence of FeCl₂ (10 mol%) andα,α-bis(3,5-bistrifluoromethylphenyl)prolinol (10 mol%), [3+2] cycloaddition of azomethine ylides with electronic-deficient olefins underwent smoothly in CH₃CN at room temperature to generate the desired endo-adducts in moderate to good yields and enantioselectivities. This is the first example of Fe(II)/N,O-ligand catalyzed 1,3-dipolar enantioselective cycloaddition reaction of azomethine ylides.