Oxidative Dehydrogenation Coupling Reaction Catalyzed By Ethoxycarbonyl Copper Porphyrin

Allylic esters are versatile key motifs with extensive applications in synthesis and importantly ubiquitous cores in many natural products,pharmaceutical molecules and fine chemicals.Therefore,continuous interests have been sparked in the access of efficient,convenient,straightforward and highly atom-economic methods for allylic esters via C-X?C,O,N,etc.?bonds construction in recent years.Direct oxidative cross dehydrogenative coupling?CDC?strategy for the synthesis of allylic esters using allylic C–H substrates and acids as the starting materials is more atom-economic than tandem C–H oxidative esterification between acid precursors?aldehydes,arylmethanes,alkenes or alkynes?and alkenes.In recent years,we have successfully applied CuTECP?5,10,15,20-tetra?ethoxycarbonyl?porphyrinato?copper?II?and FeTECPCl[Chloro?5,10,15,20-tetra?ethoxycarbonyl?porphyrinato?iron?III?]to esterification of 1,4-dioxane C?sp3?-H with carboxylic acid.In order to further expand the scope of application of the catalysts,the CDC esterification reaction between allyl C?sp³?-H and benzoic acid derivatives catalyzed by metalloporphyrins was discussed in this paper.The main research contents are as follows:1.Tetraphenylporphyrin,tetrapentafluorophenyl porphyrin,tetrakis-ethoxycarbonyl porphyrin and their corresponding complexes CuTPP,CuF₂₀TPP,MnTECPCl,FeTECPCl,CoTECP,NiTECP,CuTECP,AgTECP,PdTECP,CuTPP,CuF₂₀TPP,and?FeTECP?₂O were synthesized characterized by UV,NMR and HRMS.2.In this paper,porphyrin complexes have been applied to catalyze Kharasch-Sosnovsky reaction for the first time.By screening a large number of porphyrin metal complexes CuTPP,CuF₂₀TPP,MnTECPCl,FeTECPCl,CoTECP,NiTECP,CuTECP,AgTECP,PdTECP,CuTPP,CuF₂₀TPP,and?FeTECP?₂O,and comparing with traditional inorganic catalysts copper acetate and copper chloride,we found that only copper and iron catalysts have catalytic activity.5,10,15,20-tetrakis?ethoxycarbonyl?porphyrin has the best catalytic activity among all the catalysts.Secondly,we optimized the catalyst equivalent,oxidant type,solvent type,reaction temperature,and reactant concentration.The optimum reaction condition was benzoic acid?0.5mmol?,cyclohexene?5 mmol?,catalyst CuTECP?0.1 mol%?and benzene?1 mL?at 100?for24 h.Based on the above optimum conditions,we extended the bimolecular oxidative cross-coupling reaction and found that the coupling reactions of electron-deficient benzoic acid,electron-rich benzoic acid,cyclic olefin,and chain olefin have good adaptability in more than40 expanded substrates.3.At the same time,when we reduced the equivalent of CuTECP catalyst to one in ten thousand,the yield of the reaction could still reach 81%,which was the highest turnover number reported by Kharasch-Sosnovsky reaction thus far.In addition,we carried out free radical trapping experiments and ion reaction process verification experiments.It was proved that the allyl esterification catalyzed by CuTECP was a single electron transfer reaction of free radicals.