Study On The Synthesis Of 1,3-Azole-Substituted Pvrazincs And The Thermal Behavior

In this thesis,the synthesis of pyrazines derivatives via base catalyzed double C-H bond to promote directly oxidative cross-dehydrogenative coupling reactions was studied.The results obtained are as follows:1?A new synthesis method for the highly regioselective production of 1,3-azole-substituted pyrazines has been designed based on the advantages and practicality of C-H bond activation(Scheme 1).The method adopted a one-pot cooking operation,and the 1,3-azole-substituted pyrazine derivatives could be prepared in one step by direct coupling reaction in the air using an economically available pyrazine nitrogen oxide compounds and 1,3-azole compounds as the substrates and the alkaline as the catalyst.Among them,the optimal conditions for this coupling reaction: the molar ratio of pyrazine nitrogen substrate to azole is 1:2,2.5 equivalent of tBu OLi as the catalyst,1 equivalent of TBAB(Tetrabutylammonium bromide)as the additive,2 m L xylene as the solvent,160 °C,24 h,under air.Moreover,this reaction had a good substrate universality,and eleven 1,3-azole-substituted pyrazine derivatives were finally obtained in a yield as high as 67%.2?Compounds 3a and 3d were selected as representatives,and the thermal behavior study of the compounds(3a and 3d)were carried out initially using the TG-DTG combination technique.The results showed that when the temperature was raised to 237 °C,mass loss rate of 3a reached the maximum value,accompanied with mass loss rate of 94.9%;when the temperature was raised to 312 °C,mass loss rate of 3d reached the maximum value,accompanied with mass loss rate of 97.8%.Therefore,thermogravimetric analysis can show that compounds 3a and 3d have good thermal stability at room temperature,which provides an effective theoretical basis for their subsequent application.3?Based on the previous relevant references and analysis of the experimental results of this experiment,a possible experimental reaction mechanism was proposed.A plausible reaction mechanism was outlined in the following figure.