Perfluoromethylcyclohexane-toluene

Copper bromide and pentakis-A-(heptadecafluoroundecyl)-l,4,7-triazeheptane (1 in Figure 10.9), along with an initiator, ethyl-2-bromoisobutyrate (2 in Figure 10.9), in a perfluoromethylcyclohexane-toluene biphase efficiently catalyse the polymerization of methyl methacrylate, with a conversion of 76 % in 5 h at 90 °C. The resultant polymer has a Mn = 11100 and a molar mass distribution of 1.30. After polymerization, the reaction was cooled to ambient temperature, the organic layer removed and found to contain a copper level of 0.088 % (as opposed to 1.5% if all the catalyst were to have remained in the polymer). A further toluene solution of monomer and 2 could be added,... 

Dinh is illustrative of the methods and their potential (Figure 4).1261 Hydrosilylation of enones like cydo-hexenone was conducted in two different ways. Under biphasic reaction conditions, an organic solvent like toluene containing the enone and phenyl-dimethyl silane was heated with a fluorocarbon solvent (perfluoromethylcyclohexane) containing a fluorous rhodium catalyst. The hydrosilylation reaction occurred over 10 h, and the reaction mixture was cooled and the phases were separated. Distillation of the residue from the organic phase gave the hydrosilylated products in excellent isolated yields... 

The fluorous biphasic catalysis concept was successfully demonstrated first by hydroformylation of 1-decene carried out in perfluoromethylcyclohexane and toluene, which forms a homogeneous liquid phase at 100°C in the presence of catalyst 2 prepared in situ according to Eq. (14.1) 125,133... 

The catalytic performance of the fluoropolymer ligands 1 and 2 was first tested in the fluorous biphase hydroformylation of 1-alkenes, styrene and n-butyl acrylate. The reaction was conducted in a batch reactor in a 40/20/40 vol% hexane/toluene/perfluoromethylcyclohexane solvent mixture (10 mL). The catalyst was formed in situ by adding [Rh(CO)2(acac)] (5 rmol, P/Rh = 6) to the polymer-containing solvent mixture followed by introduction of syngas (30 bar, CO/H2 = 1/1). Table 2 summarises the results obtained. The salient features of the results are Firstly, the activity of the fluorous soluble polymer catalysts are significantly higher than that reported for solid polymer- and aqueous soluble polymer-supported rhodium catalysts.18-22 For example, the average turnover frequency (TOF) for the fluorous biphase hydroformylation of 1-decene is 136 mole aldehyde h-1 per mol of rhodium catalyst with an aldehyde selectivity of 99%. In comparison, a rhodium catalyst supported on the... 

Reaction conditions 5 imol [Rh(CO)2(acac)], P/Rh = 6, 30 bar CO/H2 (1 1), 100 °C for 1-decene and 1-hexadecane, 80 °C for styrene and n-butyl acrylate, hexane/toluene/perfluoromethylcyclohexane = 4/2/4 (mL), 15 h reaction time. The products were analysed by H NMR and the conversion and selectivity confirmed by GC. To aldehyde, olefin isomerisation accounts for the product balance. c Linear to branched aldehyde ratio, determined by HNMR. The branched product was a 1 1 mixture of enol and aldehyde, the linear aldehyde was < 1%. 

The catalytic activity of arylboronic acids 1-4 (5 mol%), which promote the model reaction of 4-phenylbutyric acid (1 equiv) with 3,5-dimethylpiperidine (1 equiv) in toluene at azeotropic reflux with removal of water (4 A molecular sieves in a Soxhlet thimble) for 1 h, and their recoverability by extraction with perfluoromethylcyclohexane, are shown in Eq. (1) and Table 1. 

As expected, 1 is more active than 4, and is recovered in quantitative yield by extraction with perfluoromethylcyclohexane. Although 2 and 3 are more active than 4, they cannot be recovered by extraction with any fluorous solvents. The amide condensation proceeds cleanly in the presence of 5 mol% of 1 the desirable amide has been obtained in 95% yield by azeotropic reflux for 15 h. In addition, the corresponding N-benzylamide has been obtained in quantitative yield by heating 4-phenylbutyric acid with benzylamine in the presence of 2 mol% of 1 under azeotropic reflux conditions for 4 h. Based on these results, the re-use of 1 has been examined for the direct amide condensation reaction of cyclohexanecarboxylic add and benzylamine in a 1 1 1 mixture of o-xylene, toluene, and perfluorodecalin under azeotropic reflux conditions with removal of water for 12 h [ Eq. (2) and Table 2] [5]. After the reaction has been completed, the homogeneous solution is cooled to ambient temperature to be separated in the biphase mode of o-xylene-toluene/ perfluorodecalin. The corresponding amide is obtained in quantitative yield from the organic phase. Catalyst 1 can be completely recovered from the fluorous phase and re-used in the recyclable fluorous immobilized phase. 

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