Selective Hydrocarbon Activation Study Of 1,2,3-Triazole Derivatives

Comparing with the traditional method of constructing carbon-carbon and carbon-heteroatom bond,the transition metal catalyzed C-H activation has the following advantages:Readily available substrates,simple operation,less by-product and so on.It fits the requirements of atomic economy and it's one of the current research hotspots.An important strategy to realize the regioselectivity of the C-H activation is to use the auxiliary function of the directing group.In this thesis,we mainly researched the regioselective arylation,nitration and acylation of arenes by 1,2,3-triazole-directed C-H activation.The main contents of the thesis are as follows:In Chapter 1,we review surveys the recent progress in C-H activation,which mainly described functional-group-directed(pyridine,azo,thiazole and amide groups et al.)C-H bond functionalization under transition metal catalysis palladium(palladium,copper and ruthenium),including the formation of C-C,C-N and C-O bonds.In Chapter 2,the reaction of 1-benzyl-4-aryl-1H-1,2,3-triazole with iodoarenes was developed.We used the reaction of 1-benzyl-4-phenyl-1H-1,2,3-triazole with 1-iodo-4-methylbenzene as a model and obtained the optimal condition as 1-benzyl-4-phenyl-1H-1,2,3-triazole(0.3 mmol),1-iodo-4-methylbenzene(0.75mmol),Pd(OAc)2(10 mol%)and AgOAc(2 eq.)in TFA(2mL)at 110? for 18 hours.Under the optimal conditions,the N(3)-ortho C-H bond on C(4)aryl of 1,4-disubstituted 1,2,3-triazoles can be selectively arylated,exclusively affording the expected structures.The diarylated products could be selectively formed when the triazole derivative beared a para substituent on C(4)aryl of the heterocycle,while the monoarylated target molecules resulted from substrates with an ortho or meta substituent.Isotope competition experiment indicated that the C-H bond cleavage may not be the rate-limiting step.In Chapter 3,an efficient Pd-catalyzed regioselective nitration of C-H bond of aromatics has been described with good functional group compatibility.We used the nitration of 4-phenyl-1-(p-tolyl)-1H-1,2,3-triazole as a model and obtained the optimal condition,which was established as 4-phenyl-l-(p-tolyl)-1H-1,2,3-triazole(0.2 mmol),Pd(OAc)2(10%mol),NaNO2(1.5 equiv.),and K2S2O8(2 equiv.)in DMSO(1.5 mL)at 120? for 18 h.With the optimized reaction conditions in hand,regioselective nitration of ortho-C-H bond of C(4)aryl can smothlly,leading to the synthesis of 1,2,3-triazoles containing nitro.The method has the advantages of high yield and low cost.The mechanism study showed that the C-H bond activation process may be Pd(?)/Pd(?)catalytic cycle,involving to the free radical mechanism.In Chapter 4,a facile and efficient method for the regioselective acetoxylation of 1,4-disubstituted 1,2,3-triazoles via Pd-catalyzed C-H bond activation was developed.We used the nitration of 4-phenyl-l-(p-tolyl)-1H-1,2,3-triazole as a model and obtained the optimal condition,which was established as 4-phenyl-l-(p-tolyl)-1H-1,2,3-triazole(0.3 mmol),Pd(OAc)2(10%mol),K2S2O8(2 equiv.)in mixed solvent of DCE/AcOH(1:1,2 mL)at 100? for 18 h.Under the optimal conditions,regioselective acetoxylation of ortho-C-H bond of C(4)aryl can smothlly,affording mono acetylated products in high yields.A range of 1,2,3-triazoles bearing acetoxyl group can be synthesized with the reaction facilely.Isotope competition experiment indicated that the C-H bond cleavage may be the rate-limiting step.