Development of 'metal-coated' microreactors as a new methodology for Microwave-Assisted, Continuous Flow Organic Synthesis (MACOS) and its application in synthetic chemistry

A new method for conducting chemical reactions in flow has been developed. The method is based upon the use of capillary microreactors, that have been internally coated with thin metallic films, which are irradiated with microwaves while the reaction solution is flowed through it. The technology has been coined Microwave-Assisted, Continuous Flow Organic Synthesis (MACOS). The thin metal films displayed catalytic activity under microwave irradiation. In addition, the chemical processes conducted with this method were tremendously accelerated due to the heat released by coupling of microwaves to metallic films.A number of protocols were developed for coating capillary reactors with different metal films. The morphologies of the metal films were studied using Scanning Electron Microscopy and Energy Dispersive X-ray analysis and the temperatures on the surface of films under microwave irradiation were accurately measured by a high definition infrared camera. The catalytic activity of metallic films under microwave irradiation was utilized in a number of applications, including Suzuki-Miyaura and Heck cross-coupling using thin Pd films, hydrosilylation of terminal alkynes using thin Au films, Diels-Alder reactions using thin Pd films. The scope of catalysis by thin films was extended effectively to difficult, multi-step reactions including the synthesis of indoles, naphthyl ketones and propargyl amines using Pd, Au and Cu-coated capillary reactors, respectively.