首页 | 本学科首页   官方微博 | 高级检索  
     检索      


A Supported Copper Hydroxide on Titanium Oxide as an Efficient Reusable Heterogeneous Catalyst for 1,3‐Dipolar Cycloaddition of Organic Azides to Terminal Alkynes
Authors:Kazuya Yamaguchi Dr  Takamichi Oishi  Tatsuyori Katayama  Noritaka Mizuno Prof Dr
Institution:1. Department of Applied Chemistry, School of Engineering, The University of Tokyo, 7‐3‐1 Hongo, Bunkyo‐ku, Tokyo 113‐8656 (Japan), Fax: (+81)?3‐5841‐7220;2. Core Research for Evolutional Science and Technology (CREST), Science and Technology Agency (JST), 4‐1‐8 Honcho, Kawaguchi, Saitama, 332‐0012 (Japan)
Abstract:An easily prepared supported copper hydroxide on titanium oxide (Cu(OH)x/TiO2) showed high catalytic performance for the 1,3‐dipolar cycloaddition of organic azides to terminal alkynes in non‐polar solvents under anaerobic conditions. The reactions of various combinations of organic azides (four examples, including aromatic and aliphatic ones) and terminal alkynes (eleven examples, including aromatic, aliphatic, and double bond‐containing ones) exclusively proceeded to give the corresponding 1,4‐disubstituted‐1,2,3‐triazole derivatives in a completely regioselective manner. For the transformation of benzyl azide and ethynylbenzene with 0.12 mol % of Cu(OH)x/TiO2, the turnover frequency was 505 h?1 and the turnover number reached up to 800. These values were the highest among those with previously reported heterogeneous catalysts including Cu(OH)x/Al2O3. The observed catalysis was truly heterogeneous and the retrieved catalyst after the reaction could be reused at least three times with retention of its high catalytic performance. It was confirmed by the UV/Vis spectrum of Cu(OH)x/TiO2 and the amount of diyne formed that the CuII species in Cu(OH)x/TiO2 were reduced to CuI species by the alkyne–alkyne homocoupling at the initial stage of the reaction (during the pretreatment of Cu(OH)x/TiO2 with an alkyne). The catalytic reaction rate for the 1,3‐dipolar cycloaddition linearly increased with an increase in the amount of in situ generated CuI species. Therefore, the in situ generated CuI species would be the catalytically active species for the present 1,3‐dipolar cycloaddition.
Keywords:alkynes  azides  copper hydroxide  dipolar cycloaddition  heterogeneous catalysis
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号