Hydroesterification of styrene derivatives catalyzed by an acidic resin supporting palladium complexes
作者:Zhenhong He、Zhenshan Hou、Yanping Luo、Yierxiati Dilixiati、Wumanjiang Eli
DOI:10.1039/c3cy00842h
日期:——
Pd–TPPTS–OTPPTS (denoted as Pd–P–OP, where TPPTS was the sodium salt of tri(m-sulfophenyl)phosphine and OTPPTS was the oxidized form of TPPTS) complexes supported on acidic resins (denoted as Pd–P–OP/resin) were prepared and employed as versatile heterogeneous catalysts for the hydroesterification of vinyl-aromatics with alcohols. The catalysts were characterized by the methods of FT-IR, XPS, N2 physisorption, XRD, TGA, SEM and 31P NMR. According to the 31P NMR results, there was a weak coordination between OTPPTS and the Pd sites. Consequently, OTPPTS was a weak ligand to the Pd sites and thus dissociated easily, acting as a protective agent of the vacant coordination site of the Pd metal sites, which allowed the substrates more access to the metal sites. In the hydroesterification of styrene, the distribution of the branched and linear esters was remarkably impacted by adding an appropriate amount of OTPPTS and the acidic resin supports. A high yield and excellent selectivity towards the branched ester were obtained when OTPPTS and TPPTS were used in equimolar amounts under optimized reaction conditions. The generality and recyclability of the catalyst for the hydroesterification of vinyl-aromatics were also examined. In addition, the poisoning and hot filtration tests indicated that Pd(0) acted as the active species in a truly heterogeneous way. A Pd–hydride mechanism was proposed for the hydroesterification over the Pd–P–OP/LSI-600 catalyst.
制备了支撑在酸性树脂(Pd-P-OP/树脂)上的 Pd-TPPTS-OTPPTS 复合物(简称 Pd-P-OP,其中 TPPTS 为三(间磺酰基苯基)膦的钠盐,OTPPTS 为 TPPTS 的氧化形式),并将其用作乙烯基芳烃与醇类进行酯化反应的多功能异相催化剂。催化剂的表征方法包括 FT-IR、XPS、N2 物理吸附、XRD、TGA、SEM 和 31P NMR。31P NMR 结果表明,OTPPTS 与钯位点之间的配位很弱。因此,OTPPTS 是钯位点的弱配位体,因此很容易解离,起到了保护钯金属位点空闲配位位点的作用,使底物有更多机会进入金属位点。在苯乙烯的水解酯化过程中,加入适量的 OTPPTS 和酸性树脂支持物会显著影响支链酯和线性酯的分布。在优化的反应条件下,以等摩尔量使用 OTPPTS 和 TPPTS,可获得高产率和对支链酯的良好选择性。研究还考察了催化剂在乙烯基芳烃酯化反应中的通用性和可回收性。此外,中毒和热过滤测试表明,Pd(0) 以真正的异构方式作为活性物种。提出了 Pd-P-OP/LSI-600 催化剂的氢酯化机理。