Study On Synthesis Of1,2,3-Triazoles And1,3-Diynes Under"Green"Conditions

One of the challenges facing chemists this century is to develop new transformations that are not only efficient, selective, and high-yielding but that are also environmentally benign. During the last decade, the topic of "green" chemistry has received increasing attention."Green" chemistry aims at the total elimination (or at least the minimization) of waste, and the implementation of sustainable processes. The utilization of nontoxic chemicals, renewable materials, solvent-free conditions and multi-component cascade reactions are the key issues in a green synthetic strategy. The main focus of this thesis has been on reviewing synthesis of1,2,3-triazoles and1,3-diynes, and introducing our work on synthesis of1,2,3-triazoles and1,3-diynes under "green" conditions. The thesis can be classified into six sections.1. Reviewing the methods for synthesis of1,2,3-triazoles.1,2,3-Triazoles have tremendous applications in various research fields due to their excellent chemical properties. Synthesis of1,2,3-triazoles was a hot subject during the past few decades. Until now, various triazoles have been synthesized through thousands of methods, and the most efficient method is Huisgen cycloaddition between azide and alkyne, that can be classified into five kinds: Huisgen cycloaddition without catalyst, copper-catalyzed Huisgen cycloaddition, ruthenium-catalyzed Huisgen cycloaddition, hydroxides and alkoxides-catalyzed Huisgen cycloaddition and the other metals-catalyzed Huisgen cycloaddition.In addition, copper-catalyzed azide-alkyne Huisgen cycloaddition (CuAAC) is the best way to synthesis of1,2,3-triazoles.2. Our group developed two kinds of catalysts for CuAAC reactions, Cu(PPh3)2NO3and [Cu(phen)(PPh3)2]NO3show outstanding catalytic activies under solvent-free conditions. The conversion can be completed in the presence of low catalytic amount of [Cu(phen)(PPh3)2]NO3at room temperature in air. This system is broad in scope and highly efficient even at very low catalyst loadings (down to50ppm). The maximums of TON and TOF are16200and2910h-1, respectively. 3. Synthesis of4,5-disubstituted-1,2,3-(NH)-triazoles via four-component cascade reactions in one-pot. Multi-component cascade reactions take the advantages of atom-economy, minimization of time, labor, power resource and waste, so it is "green" strategy in the field of synthesis. Based on our previous work, we developed an one-pot method for the synthesis of4,5-disubstituted-1,2,3-(NH)-triazoles via carbonylative Sonogashira reaction/1,3-dipolar cycloaddition of terminal acetylenes, carbon monoxide, aryl iodides, and sodium azide was developed. A series of new4,5-disubstituted-1,2,3-(NH)-triazoles were prepared readily under mild conditions.4. Synthesis of1,4-disubstituted5-iodo-1,2,3-triazoles under solvent-free conditions, and an efficient approach of converting5-iodo-1,2,3-triazoles to5-H-1,2,3-triazoles.1,4-Disubstituted5-iodo-1,2,3-triazoles have potential applications, that this kind of compound dose not only contain a1,2,3-triazoles unit and two different substituted groups, but also include a potential high reactive group5-iodo, which shows the possibility of further functionalization. We found that [Cu(phen)(PPh3)2]NO3shows high catalytic activity in Huisgen cycloaddition between organic azides and iodoalkyne. Moreover, we firstly found the efficient method for the conversion of5-iodo-1,2,3-triazoles to1,2,3-triazoles.5. Synthesis of1,3-diynes under solvent-free conditions. We review the methods for synthesis of1,3-diynes. And we introduce an economic, eco-friendly, simple and efficient method of synthesis of1,3-diynes through homocoupling of terminal alkynes. The reaction conditions are3mol%CuCl2,3mol%Et3N,60℃and neat solvent. The system is also feasible for synthesis of unsymmetric1,3-diynes through cross-coupling of different terminal alkynes.6. We provide a summary and outlook on synthesis of1,2,3-triazoles and1,3-diynes under "green" conditions.