Activating Azides and Alkynes for the Click Reaction with [Cu(aNHC)2I] or [Cu(aNHC)2]+ (aNHC = Triazole-Derived Abnormal Carbenes): Structural Characterization and Catalytic Properties
Activating Azides and Alkynes for the Click Reaction with [Cu(aNHC)2I] or [Cu(aNHC)2]+ (aNHC = Triazole-Derived Abnormal Carbenes): Structural Characterization and Catalytic Properties
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DOI：
10.1002/ejic.201300150
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发表时间：
2013-08-06
影响因子：
2.3
通讯作者：
Sarkar, Biprajit
中科院分区：
文献类型：
--
作者：
Hohloch, Stephan;Scheiffele, Damaris;Sarkar, Biprajit
中性的含碘铜（I）配合物[Cu（aNHC）（2）I] {aNHC = 1-苄基-3-甲基-4-苯基-1，2，3-三唑-5-亚基（对于6）和3-甲基-1-[2-（三唑-5-亚基）-3-甲基-4-苯基]-1，2，3-三唑-5-亚基（对于6）}。（甲硫基）苯基]-4-苯基-1，2，3-三唑-5-亚基（对于7）}和阳离子无卤铜（I）配合物[Cu（aNHC）（2）]（BF 4）{aNHC = 1-苄基-3-甲基-4-苯基-1，2，3-三唑-5-亚基，2，3-三唑-5-亚基（用于8）、3-甲基-1，4-二苯基-1，2，3-三唑-5-亚基（用于9）、3-甲基-1-[2-（甲硫基）苯基]-4-苯基-1，2，3-三唑-5-亚基（对于10）和1-均三甲苯基-3-甲基-4-苯基-1，2，3-三唑-5-亚基（对于11）}，两者均含有两个单齿异常卡宾配体（aNHC），以[Cu（CH 3CN）（4）]（BF 4）和相应的三唑盐为原料，合成了三唑类配合物。通过简单地改变三唑盐的抗衡阴离子而保持金属前体相同，可以选择性地合成这两种配合物。通过元素分析和光谱方法对配合物进行了表征。6和11的单晶X射线衍射分析进行了研究。在6中，铜（I）中心是三配位的，其几何形状介于三角平面和T形之间。在无卤化物的11中，铜（I）中心通过两个异常碳烯配体线性配位。所有的配合物作为催化剂在Huisgen [3+2]环加成反应叠氮化物和炔，他们表现出优异的效率在净条件下。含卤素络合物6和7与不含卤素的情况8-11的效率之间的比较显示，不含卤素的Cu-aNHC络合物比它们的含卤素对应物显著更有效。利用多种叠氮化合物和几种炔类化合物筛选出最佳催化剂。催化剂的效率在低至0.005摩尔%的负载量下得以保持。还进行了机制研究。
Neutral, iodido-containing copper(I) complexes [Cu(aNHC)(2)I] {aNHC = 1-benzyl-3-methyl-4-phenyl-1,2,3-triazol-5-ylidene (for 6) and 3-methyl-1-[2-(methylthio)phenyl]-4-phenyl-1,2,3-triazol-5-ylidene (for 7)} and cationic, halide-free copper(I) complexes [Cu(aNHC)(2)](BF4) {aNHC = 1-benzyl-3-methyl-4-phenyl-1,2,3-triazol-5-ylidene (for 8), 3-methyl-1,4-diphenyl-1,2,3-triazol-5-ylidene (for 9), 3-methyl-1-[2-(methylthio)phenyl]-4-phenyl-1,2,3-triazol-5-ylidene (for 10), and 1-mesityl-3-methyl-4-phenyl-1,2,3-triazol-5-ylidene (for 11)}, both containing two monodentate abnormal-carbene ligands (aNHC), were synthesized from [Cu(CH3CN)(4)](BF4) and the corresponding triazolium salts. It was possible to selectively synthesize both kinds of complexes by simply variing the counter-anion of the triazolium salts and keeping the metal precursor the same. All complexes were characterized by elemental analysis and spectroscopic methods. 6 and 11 were studied with single-crystal X-ray diffraction analyses. In 6, the copper(I) center is tricoordinated, and its geometry is in between trigonal planar and T-shaped. In halide-free 11, the copper(I) center is linearly coordinated by two abnormal-carbene ligands. All complexes were tested as catalysts in the Huisgen [3+2] cycloaddition reaction between azides and alkynes, and they showed excellent efficiencies under neat conditions. A comparison between the efficiencies of the halide-containing complexes 6 and 7 and the halide-free cases 8-11, shows that the halide-free Cu-aNHC complexes are significantly more efficient than their halide-containing counterparts. The best catalyst was used for a substrate screening by utilizing a variety of azides and a couple of alkynes. The efficiency of the catalyst was maintained with loadings as low as 0.005 mol-%. Mechanistic studies were carried out as well.