Tetranuclear and trinuclear copper( i ) pyrazolates as catalysts in copper mediated azide–alkyne cycloadditions (CuAAC)
Tetranuclear and trinuclear copper( i ) pyrazolates as catalysts in copper mediated azide–alkyne cycloadditions (CuAAC)
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四核和三核吡唑铜(i)作为铜介导的叠氮化物-炔环加成反应(CuAAC)的催化剂
DOI：
10.1039/d1dt04026j
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发表时间：
2021
影响因子：
4
通讯作者：
Dias, H. V.
中科院分区：
文献类型：
--
作者：
Patterson, Monika R.;Dias, H. V.
均配型四核吡唑铜（I）配合物{[3，5-（t-Bu）2 Pz]Cu}4、{[3-（CF 3）-5-（t-Bu）Pz]Cu}4和{[4-Br-3，5-（i-Pr）2 Pz]Cu}4是叠氮-炔环加成反应（CuAAC）的优异的独立催化剂。这项工作表明，一系列的吡唑类化合物，包括那些具有给电子和吸电子基团的吡唑基骨架上的空间要求的取代基，可以作为有效的配体支持四核铜催化剂。然而，与四聚体和高度氟化的{[3，5-（CF 3）2 Pz]Cu}3相反，由相对富电子的吡唑类化合物负载的三核铜（I）配合物如{[3，5-（i-Pr）2 Pz]Cu}3和{[3-（CF 3）-5-（CH 3）Pz]Cu}3在CuAAC中显示出差的催化活性。使用蒸气压渗透法检查了这些铜（I）吡唑在溶液中的聚集的行为和程度。铜（I）配合物如{[3，5-（CF 3）2 Pz]Cu}3和{[3-（CF 3）-5-（t-Bu）Pz]Cu}4与吸电子的吡唑配合物在溶液中被不同程度地分解，产生较小的聚集体，而那些如{[3，5-（i-Pr）2 Pz]Cu}3和{[3，5-（t-Bu）2 Pz]Cu}4与富电子的吡唑配合物保持完整。此外，进行动力学实验，以了解不寻常的活性四核铜（I）吡唑系统。
Homoleptic, tetranuclear copper(I) pyrazolates {[3,5-(t-Bu)2Pz]Cu}4, {[3-(CF3)-5-(t-Bu)Pz]Cu}4, and {[4-Br-3,5-(i-Pr)2Pz]Cu}4 are excellent stand-alone catalysts for azide–alkyne cycloaddition reactions (CuAAC). This work demonstrates that a range of pyrazolates, including those with electron donating and electron-withdrawing groups to sterically demanding substituents on the pyrazolyl backbones, can serve as effective ligand supports on tetranuclear copper catalysts. However, in contrast to the tetramers and also highly fluorinated {[3,5-(CF3)2Pz]Cu}3, trinuclear copper(I) complexes such as {[3,5-(i-Pr)2Pz]Cu}3 and {[3-(CF3)-5-(CH3)Pz]Cu}3 supported by relatively electron rich pyrazolates display poor catalytic activity in CuAAC. The behavior and degree of aggregation of several of these copper(I) pyrazolates in solution were examined using vapor pressure osmometry. Copper(I) complexes such as {[3,5-(CF3)2Pz]Cu}3 and {[3-(CF3)-5-(t-Bu)Pz]Cu}4 with electron withdrawing pyrazolates were found to break up in solution to different degrees producing smaller aggregates while those such as {[3,5-(i-Pr)2Pz]Cu}3 and {[3,5-(t-Bu)2Pz]Cu}4 with electron rich pyrazolates remain intact. In addition, kinetic experiments were performed to understand the unusual activity of tetranuclear copper(I) pyrazolate systems.