Supported Fluorous Phase Catalysis on PTFE, Fluoroalkylated Micro‐ and Meso‐porous Silica

Abstract

New perfluoroalkylated micro-and mesoporous silica, along with powdered Teflon, have been evaluated as solid supports for supported fluorous phase catalysis in a model reaction; the hydrogenation of styrene using a fluorous analogue of Wilkinsons catalyst. Each support material showed catalytic activity and catalyst-leaching behaviour related to its surface area and was consistent with supported liquid phase catalysis. However, catalyst decomposition on the silica supports resulted in substantial reductions in activity on catalyst recycle. In contrast, although activity and leaching levels on PTFE were poorer, the supported catalyst was recycled successfully.

Insoluble Perfluoroalkylated Polymers: New Solid Supports for Supported Fluorous Phase Catalysis

“…Both of the perfluorinated polymers, P7c and P8c, gave recycling results with reasonable catalytic activity observed in the third run for both substrates, better than those obtained with FRPSG. These results are entirely consistent with previous observations from us [9,17] and others [8,10] on metal-catalysed reactions using FRPSG, which highlight the poor recyclability of such systems, something that has been ascribed to catalyst decomposition on the acidic silica surface. For all of the fluorinated supports the amount of palladium leaching into the organic phase was monitored by ICP-OES for each catalytic run and reported as a percentage of the original charge.…”

“…The well-established hydrogenation of styrene with fluorinated analogues of Wilkinsons catalyst has become a benchmark for comparing the efficacy of different fluorous-based catalyst/product separation techniques [9,[18][19][20] and was used here to evaluate the performance of the new fluorous-functionalised polystyrene resins in a second phase of testing. To this end, the supported rhodium catalyst 7 was prepared by the reaction of [RhClA C H T U N G T R E N N U N G (C 2 H 4 ) 2 ] 2 with the perfluoroalkylated triarylphosphine in toluene in the presence of the fluorinated beads followed by removal of the solvent under reduced pressure.…”

“…Immobilised perfluoroalkylated chiral copper bis(oxazolines) catalysed successfully the enantioselective glyoxylate-ene reactions, but chiral induction decreased substantially by the third catalyst recycle, something that the authors ascribe to an unfavourable influence of the silica gel. [7] Likewise, Biffis [8] and ourselves [9] reported signs of catalyst decomposition and the fluorous silica support changing colour in the solventless silylation of 1-octanol using dirhodium(II) perfluorocarboxylates and the hydrogenation of styrene with perfluoroalkylated analogues of Wilkinsons catalyst respectively, whilst Pozzis flu-orous chiral CoA C H T U N G T R E N N U N G (salen) catalyst was completely inactive for the hydrolytic kinetic resolution of terminal epoxides when it was supported on fluorous silica. [10] The problems described above have led us and others [11,12] to prepare new, non-silica based, well-defined, highly fluorinated solid supports for transition metal based fluorous catalysts.…”

“…[3][4][5][6][7][8][9] One of the most utilised strategies has employed fluorous functionalised silicas as the immobilising agent, although this approach has a number of limitations in terms of both catalyst recycle and stability. For example, Bannwarth has described the use of an air-stable, perfluoroalkyl functionalised Pd(II) complex immobilised onto fluorous reverse-phase silica gel for Suzuki-Miyaura reactions in DME and water.…”

Catalysis of Intramolecular Morita–Baylis–Hillman and Rauhut–Currier Reactions by Fluorous Phosphines; Facile Recovery by Liquid/Solid Organic/Fluorous Biphase Protocols Involving Precipitation, Teflon® Tape, and Gore‐Rastex® Fiber

“…[3,5] In conceptually related recycling efforts, others have applied fluorous silica gel. [6][7][8][9][10] In two feasibility studies, we described (1) the use of Teflon shavings as a mechanical support for recycling the fluorous phosphine PA C H T U N G T R E N N U N G [(CH 2 ) 2 R f8 ] 3 , which is an effective Lewis base or nucleophilic catalyst for additions of alcohols to propiolate esters (n-octane, 65 8C), [3] and (2) the use of Teflon tape as an adsorbent for recycling a rhodium hydrosilylation catalyst derived from ClRh{PA C H T U N G T R E N N U N G [(CH 2 ) 2 R f6 ] 3 } 3 (dibutyl ether, 55 8C). [5] We were naturally interested in broadening the applicability of these protocols, and evaluating a wider range of fluoropolymer supports.…”