Design Synthesis And Fluorescence Properties Of Several Heterocyclic Aromatic Halides Based On Gattermann Reaction

The synthesis and application of heterocyclic compounds have always been one of the vital research topics in the field of organic chemistry.Among the five-membered heterocyclic compounds,1,3,4-thiadiazole,1,3,4-oxadiazole and 1,2,4-triazole,not only widely be used in the synthesis of pharmaceuticals and pesticides,but also played an important role in the study of organic light-emitting materials and fluorescent probes.Therefore,the design and synthesis of nitrogen-containing aromatic heterocyclic compounds is of great significance in practical applications.The main contents of this paper are as follows:(1)Based on Gattermann reaction,four kinds of aromatic halogenated compounds with different heterocycles were synthesized by one-pot reaction.Using P-methoxybenzoic acid and corresponding urea compounds as starting materials,via dehydration-condensation reaction,three different heterocyclic aromatic amines were obtained.Then,four kinds of compounds were synthesized based on Gattermann reaction in one-pot reaction,including 2-chloro-5-(3-chloro-4-methoxy-phenyl)-1,3,4-thiadiazole(L1),2-bromo-5-(3-bromo-4-methoxy-phenyl)-1,3,4-thiadiazole(L2),2-bromo-5-(3-bromo-4-meth oxy-phenyl)-1,3,4-oxadiazole(L3),3-bromo-5-(3-bromo-4-methoxy-phenyl)-1H-1,2,4-triazol e(L4),where L1 and L4 are new compounds.The structures of the four compounds were characterized by analysis methods of HRMS and NMR.According to the reaction process,the synthesis reaction mechanism was inferred.Fluorescence spectrum test shows that compound L1 as probe has the best fluorescent property in the four compounds.In V_DMSO:V_H2O=2:1 system,probe L1 has a good recognition of TNP,the detection limit of probe L1 is 0.78×10^-6mol·L^-1.According to the density functional theory,the fluorescence quenching mechanism of probe L1 to TNP may be the photoinduced electron transfer(PET)mechanism.The test of light stability and different water samples indicated that probe L1 has practical significance for the detection of TNP.(2)Designed and synthesized two kinds of N-bromine-[1,3,4]-thiadiazole-pyrazole-carbaldehydesBased on the above reactions,the intermediates N-(1-p-methoxyphenyl-ethylene)-N'-(5-p-bromophenyl-[1,3,4]thiadiazole-2-yl)-hydrazine(B1)and N-(1-phenyl-ethylene)-N'-(5-p-bromophenyl-[1,3,4]thiadiazole-2-yl)-hydrazine(B2)were synthesized.Then the target compounds 3-p-methoxyphenyl-1-(5-p-bromophenyl-[1,3,4]thiadiazole-2-yl)-1-H-pyrazole-4-carbaldehydes(A1)and 3-phenyl-1-(5-p-bromophenyl-[1,3,4]thiadiazole-2-yl)-1-H-pyrazole-4-carbaldehydes(A2)were obtained by the methods of Vilsmeier-Haack cyclization reaction.Above all,the intermediates synthesized and target compounds both are new compounds.Their structures were characterized by HRMS,NMR.Fluorescence quantum yield and fluorescence spectrum test show that probe A1 has better fluorescence properties.As above,in V_DMSO:V_H2O=2:1 system,probe A1 also has high selectivity and sensitivity to TNP,the detection limit of probe A1 is 5.2×10^-6mol·L^-1.On the same condition,through the test of different water samples and light stability,it was indicated that probe A1 has certain application value for detection of TNP in the water as well as probe L1.