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
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The fluorous phosphine P[(CH2)3Rf8] 3 [1, Rf8=(CF2)7CF3; 10 mol%] catalyzes intramolecular Morita-Baylis-Hillman reactions of O=CH-(CH 2)nCH=CH(C=O)R [n/R=2/Ph (2a), 2/S-i-Pr, 3/p-tol] in acetonitrile at 60-72°C. Upon cooling, 1 precipitates and is recycled. The products HOCH(CH2)nCH=C(C=O)R are isolated from the supernatant (78-96%). The educt i-PrS(C=O)CH=CH(CH2) 2CH=CH(C=O)S-i-Pr similarly undergoes a Rauhut-Currier reaction to give i-PrS(C=O)CH2CH(CH2)2CH=C(C=O)S-i-Pr (71-73%). In the case of 2a, reactions are also conducted in the presence of Teflon® tape or Gore-Rastex® fiber. The catalyst now precipitates onto the fluoropolymer support, mechanically facilitating recycling. For each reaction, three to five cycles are conducted. HPLC or GC monitoring of the rates show low activity losses, with Gore-Rastex® fiber giving better results than Teflon® tape, presumably due to a higher surface area. © 2008 Wiley-VCH Verlag GmbH & Co. KGaA.
author list (cited authors)
Seidel, F. O., & Gladysz, J. A.