Design And Synthesis Of Solid Organic Bases And Their Supported Palladium Catalysts For Carbon-Carbon Bond Formation

Carbon-carbon bond construction is the basis of organic chemistry,there are many C-C building methods have been reported.Almost all C-C bond formation reactions require the participation of the catalyst,and the homogeneous organic catalyst or metal catalyst residue has been difficult to solve.Design and synthesize a highly efficient,easily separable,recyclable C-C bond-forming heterogeneous catalyst has been the goal pursued by catalytic workers.Organic bases can catalyze some simple C-C bond formation reactions due to basicity and their electron-rich sites,such as Aldol,Henry and Knoevenagel reaction.Besides,most organic bases contain rich electron sites that can also be used as ligands to bind the precious metals.In this paper,a series of solid organic bases and their immobilized noble metal catalysts were designed and synthesized from the two-dimensional material graphene oxide(GO)and the porous organic polymers(POPs).The catalysts were characterized by the elemental analysis,FTIR,XRD,XPS,SEM,TEM and ICP.They are applied to the appropriate C-C bond formation reaction and show high efficiency,high selectivity,easy separation and excellent reusability.(1)Super organic base 1,1,3,3-tetramethylguanidine(TMG)was immobilized on graphene oxide by hydrogen bonding to obtain a solid organic base catalyst TMG / GO and applied to Aldol reaction.The catalyst has a comparable catalytic activity to that of homogeneous catalyst and can be reused without any activity decreased.Moreover,TMG/GO also shows a high selectivity of the Aldol product and can keep the selectivity during the reaction.The possible mechanism of TMG / GO catalyzed Aldol reaction was proposed according to the experimental results.(2)Tuning the acidic groups on the surface of graphene oxide by the esterification reaction to obtain modified GOs and the modified GOs supported 3-aminopropyltriethoxysilane catalysts are carried out in the Aldol reaction.The results show the more basic groups on the catalyst,the higher the catalytic activity;the weak acidic phenolic hydroxyl group helps to keep the Aldol product from dehydration to produce the enone product.(3)The nitrogen sites of the organic solid base TMG/GO can chelate the noble metal ions(Pd2+),and the Pd2+ can easily be reduced to Pd nanoparticles under strong basic conditions.Based on this idea,the Pd@TMG/GO catalyst was synthesized by mixed Pd(OAc)2 and TMG/GO and performed in the Heck coupling reaction.The catalyst shows excellent catalytic performance and could be applied to a scope of substrates,and can be reused several times without any activity decreased.(4)Homogeneous 1,10-phenanthroline catalysts have been reported for use in the coupling reaction of benzene with halogenated aromatic hydrocarbons.However,the catalyst isn't easily separated from the reaction system.We polymerized 1,10-phenanthroline by Friedel-Crafts reaction to get a basic porous organic polymer catalyst.This catalyst shows excellent catalytic performance in the coupling reaction of iodobenene with benzene.It also can be applied to aromatic iodide and bromide with benzene(not suitable for aromatic chloride),and can be easily separated from the catalytic system and reused several times.(5)3,5-carbazolopyridine porous organic polymer(CNP-2)and 2,6-carbazolopyridine porous organic polymer(CNP-1)was prepared via a novel spatial-modulation approach.Pd(OAc)2 are easily access to the pyridine sites of CNP-2 than that of CNP-1 to form a complex catalyst(Pd@CNP-2).Pd@CNP-2 shows efficient and additive-free cyanation of aryl halides.The resultant catalyst exhibits high-performance activities towards the synthesis of benzonitriles,including high yield of the products,excellent cycling ability and stability,and wide variety of functional group tolerance.