Highly Efficient And Green Synthesis Of1,2,3-triazoles

Among the various five-membered heterocyclic compounds,1,2,3-triazolespossess a widely range of applications as a very important three-nitrogen aromaticheterocyclic rings. Up to now, it has been widely used in the field of biomedicine,pesticides, biological and materials science and acted as a pivotal role. Owing to itsapplications in many expanding areas, the increasing concern about the preparation of1,2,3-triazoles has attracted much attention again and has obtained a entertainingprogress in recent years. In this dissertation, firstly we uses inexpensive, readilyavailable support material, such as waste eggshells or agricultural rice husks todevelop two new environment friendly heterogeneous catalysts for the construction of1,2,3-triazoles under microwave-assisted with high reaction efficiency and highselectivity through the strategy of the one-pot three-component reaction without theisolation of the dangerous organic azides. And various methods have been used tocharacterize the catalysts. In addition, we described cyclodextrin loading coppercatalyst for the synthesis of a series of β-hydroxy1,2,3-triazoles via three-componentone-pot reaction under room temperature. The novel catalyst was characterized by1HNMR and13C NMR in detail. Two-dimensional ROESY NMR experiment wasconducted to examine the potential spatial proximities and further explore thecatalytic mechanism. Three parts of this dissertation are detailed in the following.1In the second chapter, we put the idea of turning waste into treasure into practicalaction, which based on taking advantage of waste egg shells as environmentallyfriendly support to develop a novel efficient heterogeneous catalyst ESPs-CuBr.Firstly, we designed and synthesized a series of novel terminal alkyne derivativesfor the construction of1,2,3-triazoles with high reaction efficiency and highselectivity via the strategy of three-component one-pot reaction with halides andsodium azide using the ESPs-CuBr without the isolation of the unstable andhazardous organic azides. And various methods such as fourier transform infra red(FT-IR), thermo gravimetry (TGA), X-ray diffraction (XRD), atomic absorptionspectroscopy (AAS), transmission electron microscopy (TEM), scanning electronmicroscopy (SEM), were used to fully characterize the catalyst. The TGA curve ofESPs-CuBr reveals that the egg shell powder more or less contain organiccompounds like proteins. Comparing with the calcium carbonate loading withCu(I), the ESPs-CuBr showed higher catalytic activity under the same conditionswhich shows the important role of the organic ingredient. The1,2,3-triazoles canbe readily obtained in80－96%with high region-selectivity and on multi-gramscale by the reaction of terminal alkynes, NaN3and aryl/alkyl halides in waterunder microwave irradiation condition. It also showed good reusability, could beeasily recovered through filtration and reused at least six times with no significantchange of catalytic performance. In a word, the practical application of thecatalyst has an important significance.2We reported another novel catalyst for the synthesis of1,2,3-triazoles by a one-pot three-component reaction of terminal alkynes, NaN3and aryl/alkyl halides in thepresence of RiHusk@CuBr based on waste agricultural rice hulls which isabundant in our country. The outstanding advantage of this method is that itavoids the design of the complicated structure of catalyst which istime-consuming and energy-consuming, even not environmentally friendly. Thestructural diversity of1,2,3-triazoles were easily obtained in good to excellentyields ranging from80to97%in water under microwave conditions. Large-scaleexperiments showed the feasibility of applying this method in a preparative scale.Moreover, it still maintained good catalytic activity after4consecutive reactionswhen10times substrates were taken. The novel method which inspires us how todesign new heterogeneous catalyst, does not only cater to the concept of greenchemistry, but also fully exploit the potential value of the waste. Specificcharacterizations of the catalyst were taken as shown in Chapter II.3In the last chapter of this dissertation, we firstly designed and synthesized a noveland efficient catalyst based on β-cyclodextrin-modified ligand chelating CuBr forthe synthesis of a series of β-hydroxy1,2,3-triazoles via the strategy of thethree-component one-pot reaction in water under room temperature conditions,the TON and TOF of this reaction system can reach up to3.0×104and6.9×104h-1,separately. The novel catalyst was detailedly characterized by1H NMRspectroscopy and13C NMR spectroscopy. Two-dimensional ROESY NMRexperiment was conducted to examine the potential spatial proximities among thedifferent protons of the catalyst. To further explore the catalytic mechanism, therole of the β-CD-fragment in the reaction was evaluated by ROESY NMR.