Visible Light Catalytic Oxidation Amine Synthesis Imine By Cobalt Thioporphyrazine

Imine（C=N）compounds are important intermediates for the synthesis of fine chemicals.It is consistent with the concept of green sustainable development to produce imines by the photooxidation of amines with activated molecular oxygen.The sulfur-containing tetraaza metal porphyrins have strong absorption in the visible light region,and they can mimic cytochrome P-450 monooxygenase under mild conditions,and have attracted wide attention as a green and efficient bionic photocatalyst.In this dissertation,the photocatalytic oxidation of amine to imine was investigated using the porphyrins as visible light catalysts and molecular oxygen as oxidant under mild conditions.The main work is as follows:（1）In the homogeneous amines oxidation systems with tetrakismethyltetra（1,4-dithiazolyl）-tetraazazacozenoporphyrin（CoPz（hmdtn）₄）as visible light catalyst,the effects of solvent,light wavelength and intensity on photocatalytic activity were investigated systematically.The experimental results show that the conversion of benzylamine is 90%in the acetonitrile solution with CoPz（hmdtn）₄ as the photocatalyst and molecular oxygen as the oxidant under visible light（λ≥420nm）irradiation,and the selectivity of the product N-benzylzenzylieneamine is up to 99%.According to ESR technique and quenching experiment,the main reactive oxygen species in this photocatalytic process are singlet oxygen（¹O₂）and superoxide anion radical(O₂^·-)And POD-DPD detection and GC-MS analysis proved that the photocatalytic intermediates were H₂O₂ and NH-imine.The kinetic experiments of the photocatalytic oxidation show that the reaction is a first order reaction.（2）Using CoPz（hmdtn）₄ as a visible light catalyst,the photocatalytic oxidation of unsymmetrical secondary amines in homogeneous system was studied.The effect of additives on the selectivity of the oxidation product imine was investigated.The experimental results show that the auxiliary acid or base in the acetonitrile solution can significantly affect the conversion of secondary amine and the selectivity of the oxidation product imine.When the organic base DBU is used as an auxiliary,the asymmetric secondary amine can be oxidative dehydrogenated to an imine with high selectivity.The conversion of N-benzylmethylamine was 79.8%under light without DBU for 4h,and the selectivity of the oxidation products benzethylenemethylamine and N-benzylalkenylamine were 52.6%and 45.2%,respectively.The conversion of N-benzylmethylamine was 95.3%under light irradiation with DBU for 3 h,and the selectivity of the oxidation products of benzethylenemethylamine and N-benzylalkenylamine was 92.5%and 5.5%,respectively.The main reactive oxygen species in this photocatalytic process are singlet oxygen（¹O₂）and superoxide anion radical(O₂^·-),which were proved by quenching experiments.According to the POD-DPD technique detection,the photocatalytic intermediate was H₂O₂.（3）A supported catalyst（CoPz（hmdtn）₄/Fe₃C-NCNT）was obtained by loading CoPz（hmdtn）4 on a magnetic iron-based carbon-nitrogen material and characterized by Raman,XRD,TEM and XPS and other techniques.Then it was applied to photocatalytic oxidation of amines,and the influence of experimental conditions such as reaction solvent,catalyst loading and light intensity on photocatalytic activity was investigated.The experimental results show that when the loading of the catalyst is 5 wt.%,the conversion of benzylamine is 51.0%under visible light（λ≥420nm）in ethyl acetate solution,and the selectivityoftheproductN-benzylalbuteneaminewasover90.3%.CoPz（hmdtn）4/Fe3C-NCNT shows excellent photocatalytic activity,while Fe3C-NCNT has almost no photocatalytic activity.The main reactive oxygen species in this photocatalytic process are singlet oxygen（¹O₂）and superoxide anion radical(O₂^·-),which was proved by ESR technique and quenching experiments.According to the POD-DPD detection and GC-MS analysis,the photocatalytic intermediates were H₂O₂ and NH-imine.