Heterogenization of ferrocene palladacycle catalysts on ROMP-derived monolithic supports and application to a Michael addition
作者:Mavila Sudheendran、Simon H. Eitel、Stefan Naumann、Michael R. Buchmeiser、René Peters
DOI:10.1039/c4nj01253d
日期:——
The anchoring of well-defined molecular catalysts on a surface is an attractive strategy to develop sustainable catalytic processes. This article describes the first syntheses of monolith-supported ferrocene palladacycle catalysts. Monolithic supports were prepared via ring-opening metathesis polymerization (ROMP) using the “1st generation Grubbs catalyst”. Fluorinated carboxylates were surface-grafted utilizing living Ru-termini. The immobilization of the palladacycles onto the monolithic support was accomplished by ligand substitution on the fluorinated carboxylates of the graft polymer. An investigation of these supported catalysts on the efficiency and reusability under different reaction conditions in a direct Michael addition generating a quaternary C-atom is reported. Whereas stereoselectivity was found to be significantly lower than in a comparable homogeneous system, Pd-leaching was not detected in all analyzed samples indicating a permanently immobilized catalyst system.
将定义明确的分子催化剂锚定在表面是开发可持续催化过程的一种极具吸引力的策略。本文首次介绍了整体支撑二茂铁泛酰循环催化剂的合成。使用 "第一代格拉布斯催化剂 "通过开环偏聚(ROMP)制备了单片支撑物。氟化羧酸盐是利用活的 Ru-端基进行表面接枝的。通过在接枝聚合物的氟化羧酸盐上进行配体置换,实现了将帕拉代二环固定在整体载体上。报告对这些支撑催化剂在不同反应条件下生成季 C 原子的直接迈克尔加成反应中的效率和可重复使用性进行了研究。虽然发现立体选择性明显低于同类均相体系,但在所有分析样品中均未检测到钯浸出现象,这表明催化剂体系是永久固定的。