Highly cross-linked imidazolium-based materials,obtained by radical oligomerization of bisvinylimidazoliumsalts in the presence of 3-mercaptopropyl-modified silica gel, were used as supports for palladium catalysts. Thanks to the high imidazolium loading these materials were able to support a high amount of the metal (10 wt%). Such materialswere characterized by several techniques (13C magic angle spinning nuclear magnetic resonance, the Brunauer–Emmett–Teller technique, X-ray photoelectron spectroscopy, and transmission electron microscopy).The palladium catalysts displayed good activity allowing the synthesis of several biphenyl compoundsin high yields working with only 0.1 mol% of palladium loading at 50 8C in ethanol/water under batch condition. Moreover, a flow apparatus, to optimizethe efficiency of the isolation of the pure products and minimize waste (E-factor), was investigated.For the first time the palladium catalyst and base(K2CO3) were placed in two separate columns allowing an easy recovery of the products with very lowE-factor values (<4). Waste production was reduced by over 99% compared to classic batch conditions.Because of the high Pd loading only 42 mg of catalysts were employed in the Suzuki reaction between 160 mmol of 4-bromotoluene and 180 mmol of phenylboronic acid. No loss in activity was observed.
|Numero di pagine||12|
|Rivista||ADVANCED SYNTHESIS & CATALYSIS|
|Stato di pubblicazione||Published - 2013|
All Science Journal Classification (ASJC) codes
- Organic Chemistry