| In 2001,the concept of "click chemistry" was first proposed by Sharpless,who was a nobel prize-winning American chemist.The copper(I)catalyzed azide-alkyne cycloaddition reaction(CuAAC)was the most classic reaction in "click chemistry".And then,click chemistry has attracted much attention due to their application in medicine,pesticides,electrode surface modification,dyes,biochemical reagents,polymer and functional polymer materials and other fields.Due to the limitation and cost of terminal alkynes,it is necessary to explore another alternative method for the high-yielding and regioselective synthesis of 1,4-disubstituted 1,2,3-triazoles based upon enolate-mediated organocatalytic azide-aldehyde [3+2] cycloaddition reaction become a main issue after the Cu AAC reaction.The content of this paper were showed in the following:Firstly,the progress of synthesis of aryl azides,the progress of synthesis of 1,2,3-triazole by two components reaction,the progress of synthesis of 1,2,3-triazole using multicomponent reactions(MCRs)and the application progress on pharmaceutical,pesticide,industrial production and other fields were reviewed.Secondly,we have presented CuI/DBU(1,8-diazabicyclo[5.4.0]undec-7-ene)and Cu(OAc)2·H2O/DBU catalyst system,which were both highly efficient in the nucleophilic substitution of aryl iodides and sodium azide.By optimizing the reaction conditions,including the screening of catalyst,the screening of base,the choice of solvent,the amount proportional ratio control of catalytic system and the temperature,the obtained optimal reaction conditions was in hand: CuI(20 mol%),DBU(30 mol%),1.2 eq NaN3,DMSO,95℃;Cu(OAc)2·H2O(10 mol%),DBU(15 mol%),1.2 eq Na N3,DMSO,95℃.We developed a new method for the synthesis of aryl azides and a possible reaction mechanism,which has advantages in short reaction time,good universality and high yields.Thirdly,we have developed an efficient and simple two-step one-pot protocol for synthesis of 1,4-disubstituted 1,2,3-triazoles among aryl iodides,sodium azide and terminal alkynes.By optimizing the reaction conditions,we obtained the optimal reaction conditions in hand: step 1,aryl iodide(1.0 mmol),sodium azide(1.2 mmol),DMSO(3.0 mL),Cu(OAc)2·H2O(10 mol%)and DBU(20 mol%),95℃;step 2,room temperature,terminal alkyne(0.5 mmol).In this method,aryl azides produced in situ is introduced directly into the terminal alkynes without separation of the dangerous aryl azides.The method is easy to operate and has good universality.Finally,we have developed an efficient and simple two-step one-pot protocol for synthesis of 1,2,3-triazoles among aryl iodides,sodium azide and aldehydes.By optimizing the reaction conditions,we obtained the optimal reaction conditions in hand: step 1,aryl iodide(1.0 mmol),sodium azide(1.2 mmol),DMSO(3.0 mL),Cu(OAc)2·H2O(10 mol%)and DBU(20 mol%),95℃;step 2,room temperature,aldehyde(0.5 mmol).The following 1,4-disubstituted 1,2,3-triazoles could be efficiently synthesized by adding aldehydes without separating the formed aryl azides from the reaction mixture.The established protocol was suitable for a wide scope of substrates in good to excellent yields and easy to operate. |
