Organic syntheses by microwave selective heating of novel metal/CMC catalysts - The Suzuki-Miyaura coupling reaction in toluene and the dehydrogenation of tetralin in solvent-free media

摘要

The present study examines carbon microcoils (CMCs) as a novel support for Pt and Pd nanocatalysts and compares it with activated carbon nanoparticles as support for Pt and Pd metal deposits in two model microwave-assisted organic syntheses: (i) the Suzuki-Miyaura coupling reaction between phenylboronic acid and 1-bromo-4-methylbenzene in toluene solvent to produce 4-methyl-biphenyl and (ii) the dehydrogenation of tetralin (1,2,3,4-tetrahydronaphthalene) in solvent-free conditions. The microwave absorption capacity of the CMCs was more effective than the ACs support from the viewpoint of dielectric parameters (dielectric constant, dielectric loss, and loss tangent). Possible generation of microplasma (i.e., hot spots) on both supports that can impact on the progress of the reactions was monitored visually and photographed with a high-speed camera. Conventional heating (oil bath or heating mantles) of the Pd(Pt)/CMCs and Pd(Pt)/ACs system led to significantly lower product yields.