Homogeneous vs immobilized palladium catalysts for continuous flow cross-coupling chemistry
Implementation of continuous flow reactors to organic syntheses, including metal catalyzed cross-coupling chemistry applications, has been growing dramatically during the past decade. Introduction of the metal (typically palladium) into a flow cross-coupling reaction as well as its recycling has been subject to intensive research efforts. Despite the popularity of packed bed reactors and immobilized catalysts during the past 15 years, evidence of metal leaching and catalyst deactivation in most cases makes this technique unpractical on a large scale. Homogeneous (pre)catalysts in combination with an appropriate catalyst recycling technology offers several advantages such as better control of the reactivity and selectivity.
In recent years continuous flow processing, a tool classically associated with the large scale production of commodity chemicals and the oil industry, is becoming increasingly important for the production of more complex substances or materials such as active pharmaceutical ingredients (APIs) or agrochemicals (1). Considering the rapid development of this technology during the past decade, it can be assumed that in the future many industrially important chemicals will be prepared on scale using continuous flow procedures. The main advantages that are attracting both synthetic and process chemists to this enabling technology are their enhanced heat and mass transfer characteristics in microstructured devices (1,2). Reactions involving highly toxic or explosive ... ...