Heterogeneous Versus Homogeneous Palladium Catalysts for Ligandless Mizoroki-Heck Reactions: A Comparison of Batch/Microwave and Continuous-Flow Processing
作者:Toma N. Glasnov、Silvia Findenig、C. Oliver Kappe
DOI:10.1002/chem.200802200
日期:2009.1.12
transformations in continuous‐flow mode. As a suitable ligandless catalyst system for the Mizoroki–Heck couplings both heterogeneous and homogeneous Pd catalysts (Pd/C and Pd acetate) were considered. In batch mode, full conversion with excellent selectivity for coupling was achieved applying high‐temperature microwave conditions with Pd levels as low as 10−3 mol %. In continuous‐flow mode with Pd/C as a catalyst
研究了芳基碘化物和溴化物与丙烯酸丁酯的Mizoroki-Heck偶联作为模型系统,以连续流动模式进行过渡金属催化的转化。作为适用于Mizoroki-Heck偶联的无配体催化剂体系,非均相和均相Pd催化剂(Pd / C和乙酸Pd)均被考虑。在间歇模式下,在Pd含量低至10 -3的高温微波条件下,可实现具有出色耦合选择性的全转化 摩尔%。在以Pd / C为催化剂的连续流模式下,由于这些Mizoroki-Heck偶联通过涉及可溶性Pd胶体/纳米粒子的均相机理而进行,因此观察到了从非均相催化剂中大量Pd的浸出。通过使用低含量的乙酸钯作为均相钯预催化剂,在高温/高压流反应器中成功进行了连续流式Mizoroki-Heck转化。对于芳基碘化物和溴化物,都可以得到肉桂酸酯的高分离产物收率。讨论了涉及Pd催化的Mizoroki-Heck反应的机理问题。