Exploration Of New Photocatalytic System For Carbonylation Suzuki Reaction And Sonogashira Coupling Reaction

With the growing awareness of the concept of "green chemistry",using the chemical reaction principles to reduce energy consumption,eliminate environmental pollution and develope new reaction system have been attracted considerable attentions.Although cross-coupling reaction under homogeneous thermal catalytic conditions has been widely applied in organic synthesis,the requirement of elavated reaction temperature even noble metal catalyst has greatly limited its industrial application.Photocatalysis can change the absorbed solar light energy over irradiated photocatalysts into chemical energy,and has been raising widespread concern due to its mild,safety and no secondary pollution advantages.This green catalytic method has been successfully applied in conventional organic synthesis and will have a promising prospect in organic chemistry.The following two parts of research work were performed in this thesis:As is known,CO is the most common C' source in carbonylations,but the intrinsic difficulty in handling of the odorless,toxic and flammable CO gas makes its academic and industrial applicability being restricted.Therefore the exploration of various safety organic/inorganic CO surrogates to realize carbonylative reactions is appealing.In the first part,a light-induced carbonylative Suzuki reaction was achieved under mild conditions by the coupling of photo-decomposition of DMF to generate self-supplied CO with Pd-based catalysis.The effects of reaction solvent,base,palladium catalyst and reaction atmosphere has been studied,and possible catalytic reaction mechanism has been disclosed.Although precious Pd is one of the most efficient catalysts in thermally based cross-coupling reaction,it is difficult to separate from reaction substrate and recycle,making the exploration of cheap and efficient non-noble metal catalysts appealing.In the second part,CuO/TiO2 composite was synthesized by impregnation and calcinations,and the synthesized Cu-based photocatalyst was found effective in photocatalytic Sonogashira coupling reaction under visible light irradiations without the addition of non-noble metal co-catalyst and extra ligands.The effects of reaction solvent,base,Cu catalysts and reaction atmosphere has been studied,and possible catalytic reaction mechanism has been disclosed.The main conclusions obtained from our research are follows:(1)DMF can be decomposed over anatase TiO2 under UV irradiation to serve as a liquid CO surrogate,and it can be found that electron sacrificial reagent as well as photocatalytic reaction atmosphere can significantly affect the efficiency of DMF decomposition.(2)The photocatalytic DMF decomposition to CO can be successfully coupled with the carbonylative Suzuki reaction over Pd(phen)Cl2/TiO2 at room temperature under UV light irradiations without external added CO.(3)Introduction of CuO into TiO2 could not only help the full utilization of the solar light energy but also reder a built-in electric field at the interface within the composite,which can obviously improve the visible light photocatalytic performance.It was found that the synthesized CuO/TiO2 composite has a good performance in the photocatalytic Sonogashira coupling of iodobenzene even bromobenzene under visible light irradiations without the addition of non-noble metal palladium and organic ligands.In this thesis we found that(1)One novel self-supplied CO system was achieved over anatase TiO2 under UV light irradiations by the photo-decomposition of liquid DMF solvent to CO gas,which represents a new and promising strategy for realizations of carbonylative reactions.(2)The light-induced carbonylative Suzuki reaction can be achieved under mild condition via a successful coupling of TiO2-based photocatalytic decomposition of DMF to generate CO and the Pd-based catalysis.(3)The combination of p-type semiconductor CuO and n-type semiconductor TiO2 can improve the photocatalytic of TiO2.A mild photocatalytic Sonogashira coupling reaction can be realized with single Cu as heterogeneous catalyst over the synthesized CuO/TiO2 composites at room temperature.