Study On The Facile And Efficient One-pot Synthesis Of 2,4-diaryl-1,2,3-triazoles And 2,4,5-triaryl-1,2,3-triazoles

1,2,3-triazoles are very important compounds due to their versatile biological activities. Up to now, Members of this family have been widely used as antimicrobial agent, antihypertensive agent, anti-AUDS agent, and potassium channel activator, ect. A number of synthetic strategies have been developed for the synthesis of 1H-1,2,3-triazoles through decades and the most classical one is 1,3-dipolar cycloaddition of a wide variety of azides with acetylenic compound. However, few methods are available for the preparation of 2,4-diaryl- 1,2,3-triazoles and 2.4,5-triaryl-1,2,3-triazoles, as a result, study on the new synthetic methodologies for the title compounds are of great importance.As a part of continuing effort towards the further development of new synthetic methods for the title compounds, our work relied on the previous ones. Finally, α-hydroxyacetophenones were found to undergo cupric chloride catalyzed cycloaddition with phenylhydrazines in refluxing glacial acetic acid afforded corresponding 2,4-diaryl-1,2,3-triazoles and 2,4,5-triaryl- 1,2,3-triazoles in moderate to good yields. Furthermore, we hypothesized the plausible mechanism as follow taking the reaction of α-hydroxyacetophenone and phenylhydrazine as an example: α-hydroxyacetophenone with phenylhydrazine underwent similar reaction as the formation of sugar osazone to give phenylglyoxal bisphenylhydrazone, and then bisphenylhydrazone lost a proton under the oxidation of cupric chloride to form the intermediate which was transformed to bisphenylazoethylene, finally its mesoionic form lost a phenylnitrene to obtain 2,4-diphenyl-1,2,3-triazole under thermal condition.In addition, the optimization of the reaction condition involved with investigation of the reaction solvents, catalysts, reaction temperature, ect. According to this optimized reaction condition, we set out to determine the scope and variablility of the procedure and finally twenty title compounds were obtained. In summary, we have demonstrated a simple and efficient general procedure for the preparation offunctionalized 2,4-diaryl-l,2,3-triazoles or 2,4,5-triaryl-l,2,3-triazoles via a one-pot reaction of easily available materials. The essential characteristic of this method include mild reaction condition, straightforward work up procedure and comparatively higher yields.