Wang Jiawei, Martins Luísa M D R S, Ribeiro Ana P C, Carabineiro Sónia A C, Figueiredo José L, Pombeiro Armando J L
Centro de Química Estrutural, Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais, 1049-001, Lisboa, Portugal.
Chemical Engineering Departament, Instituto Superior de Engenharia de Lisboa, Instituto Politécnico de Lisboa, Rua Conselheiro Emídio Navarro, 1959-007, Lisboa, Portugal.
Chem Asian J. 2017 Aug 4;12(15):1915-1919. doi: 10.1002/asia.201700499. Epub 2017 Jun 29.
C-Scorpionate vanadium(IV) [VO Cl {κ -RC(pz) }] [pz=pyrazol-1-yl; x=0, R=SO (1); x=1, R=CH OH (2) or CH OSO Me (3)] complexes supported on functionalized carbon nanotubes (CNTs) are the first V-scorpionate catalysts used so far for the neat oxidation of o-, m- or p-xylene, with TBHP (70 % aqueous solution), to the corresponding toluic acids (main products), tolualdehydes and methylbenzyl alcohols. Remarkably, a p-toluic acid yield of 43 % (73 % selectivity, TON=1.34×10 ) was obtained with 2@CNT in a simple microwave-assisted mild oxidation procedure, using a very low catalyst charge (3.2×10 mol vs. substrate). Further, this occurred in the absence of any bromine source, what is significant towards the development of a greener and more sustainable process for oxidation of xylenes. Moreover, reuse of catalysts with preservation of their activity was found for up to six consecutive cycles. The effects of reaction parameters, such as reaction time, temperature, amount of catalyst or type of heating source, on the performance of the above catalytic systems are reported and discussed.
负载在功能化碳纳米管（CNT）上的C-蝎形钒（IV）[VOCl{κ-RC(pz)}] [pz = 吡唑-1-基；x = 0，R = SO（1）；x = 1，R = CH₂OH（2）或CH₂OSO₂Me（3）]配合物是迄今为止首次用于将邻二甲苯、间二甲苯或对二甲苯与叔丁基过氧化氢（70%水溶液）进行纯氧化反应，生成相应的甲苯酸（主要产物）、甲苯醛和甲基苄醇的V-蝎形催化剂。值得注意的是，在简单的微波辅助温和氧化过程中，使用非常低的催化剂用量（相对于底物为3.2×10⁻⁵mol），2@CNT可获得43%的对甲苯酸产率（选择性73%，TON = 1.34×10³）。此外，该反应在没有任何溴源的情况下发生，这对于开发更绿色、更可持续的二甲苯氧化工艺具有重要意义。此外，发现催化剂可重复使用多达六个连续循环且活性得以保留。报道并讨论了反应参数，如反应时间、温度、催化剂用量或加热源类型，对上述催化体系性能的影响。
