Cyclohexanol iron catalysts

The Gif-Orsay II system has been further improved in yields and simplified with respect to the reaction conditions. Cyclododecane, adamantane and cyclooctane are oxidized in 17-30 mmolar amounts and coulombic yields of around 30% with oxygen, pyridine, trifluoroacetic acid and an iron catalyst in an undivided cell. Cyclododecane afforded a 18.9% yield of alcohol and ketone in a ratio of 0.14, adamantane a 14% coulombic yield, cyclooctane and cyclohexane coulombic yields up to 48%. The C /C ratio with adamantane reached values up to 40. With paraquat or 4,4 -bipyridyl as electron transfer reagent and under otherwise the same conditions, a coulombic yield of 49% cyclohexanol and cyclohexanone (1 7.88) was obtained. In this process oxygen is reduced to superoxide, which oxidizes iron(II) to an active iron catalyst that is able to react with the hydrocarbon. 

The preparation of s-caprolactam via the Beckman rearrangement of cyclohexanone oxime was first described by Wallach in 1900. In the I.G. Faiben process, phenol was hydrogenated to cyclohexanol, at 140°-160°C and 15 bar, with a nickel oxide/silica catalyst. The cyclohexanol was del drogenated to cyclohexanone using a zinc/iron catalyst at 400°C, and the cyclohexanone oxime was formed by reaction with hydroxylamine monosidfonate. Conversion to cyclohexanone oxime was maximized at pH 7 by neutralizing the solution with ammonia. The organic layer of cmde oxime was crystallized and then isomerized to s-caprolactam with 20% oleum at 120°C. e-Caprolactam was purified and the ammonium sulfate recovered. 

We have demonstrated recently that epoxidation and hydroxyl-ation can be achieved with simple iron-porphine catalysts with iodosylbenzene as the oxidant (24). Cyclohexene can be oxidized with iodosylbenzene in the presence of catalytic amounts of Fe(III)TPP-Cl to give cyclohexene oxide and cyclohexenol in 55% and 15% yields, respectively. Likewise, cyclohexane is converted to cyclohexanol under these conditions. Significantly, the alcohols were not oxidized rapidly to ketones under these conditions, a selectivity shared with the enzymic hydroxylations. The distribution of products observed here, particularly the preponderance of epoxide and the lack of ketones, is distinctly different from that observed in an autoxidation reaction or in typical reactions of reagents such as chromates or permanganates (15). 

The commercial process for the production of nylon 6 starts with the oxidation of cyclohexane with oxygen at 160°C to a mixture of cyclohexanol and cyclohexanone with a cobalt(II) catalyst. The reaction is taken to only 4% conversion to obtain 85% selectivity. Barton and co-workers have called this the least efficient major industrial chemical process.240 They have oxidized cyclohexane to the same products using tort bu(ylhydroperoxide with an iron(III) catalyst under air (70°C for 24 h) with 89% efficiency based on the hydroperoxide. The oxidation of cyclohexanol to cyclohexanone was carried out in the same way with 99% efficiency. A cobalt catalyst in MCM-41 zeolite gave 38% conversion with 95% selectivity in 4 days at 70 C.241 These produce ferf-butyl alcohol as a coproduct. It can be dehydrated to isobutene, which can be hydro-... 

Koda and co-workers [85] studied the catalytic oxidation of cyclohexane with O2 in liquid and supercritical CO2 in the presence of acetaldehyde (cyclo-hexaneracetaldehyde = 4 1) and an iron porphyrin catalyst bearing pentafluor-ophenyl groups. The main oxidation products were cyclohexanone (2.9% yield) and cyclohexanol (2.3 % yield) with the optimum yields being achieved slightly below the estimated critical pressure of the reaction mixture. 

A cheap and safe oxidant, extremely attractive for obvious economic and environmental reasons, is oxygen. Since sonication is able to activate gases (p. 63), reactions using molecular oxygen were logically attempted. This can be the case in the oxidation of cyclohexane to cyclohexanol in the presence of iodosobenzene and the homogeneous catalyst iron tetra(pentafluorophenyl)porphyrin.i o... 

A quite original approach to selective oxidations using H2O2 is based on polymeric membranes. In one case the polymer (polydimethyl siloxane) is filled with a zeolite which encapsulates an iron complex, i.e. the homogenous catalyst is inunobilized in the membrane. The organic phase and the aqueous phase are fed at opposite sides of the membrane. This system has been used for the oxidation of cyclohexane to cyclohexanol and cyclohexanone, and the products were kept in the organic phase. In addition, Buonomenna used polymeric membranes for the oxidation of benzyl alcohol to benzaldehyde and for the oxidation of cyclohexene, both with H2O2. 

Koda and coworkers (249) have reported the air oxidation of cyclohexane in SCCO2 to yield cyclohexanol and cyclohexanone in the presence of an iron porphyrin catalyst containing the mera-pentafluorophenyl group [FeCl(TPFPP), where TPFPP = 5,10,15,20-tetrakis(pentafiuorophenyl)porphyrin]. The pentaflu-orophenyl groups were believed to enhance the catalyst solubility in the SCCO2 phase, although the solubility was not measured. The reaction required essentially stoichiometric quantities of acetaldehyde (250). The total yield of cyclohexanol and cyclohexanone was reported as 5% for 1 h reaction time at 70 C and 90 bar, which corresponded to a turnover number of 100. Selectivity to cyclohexanol and cyclohexanone was approximately equivalent at all conditions studied. 

Epoxy alcohols are the normal products of the [VO(acac)2]+(Me2C(CN)N a -catalysed oxidation of cyclic olefins by dioxygen however, cyclo-octene is oxidized exclusively to cyclo-octene oxide. The oxidation of sulphides and alkenes by peroxides with a [V(0)(acac)2] catalyst have been compared and the nature of the monoperoxovanadium(v) intermediate investigated. Complexation of a Cr(CO)3 unit to aromatic hydrocarbons enhances the benzylic positions towards attack by superoxide ion, e.g., diphenylmethane is readily converted into benzophenone. Metal porphyrin complexes ML4 continue to attract attention both as reversible oxygen-carriers (M = Fe) and oxidation catalysts (M = Mn, Fe, or Co ). For example [Mn (=0 IPh)(TPP)Cl] is believed to be involved in the oxidation of cyclohexene to cyclohexanol by PhIO in the presence of [Mn(TPP)]+ and a ferryl intermediate [Fe (0)L4] has been proposed in the oxygenation of triphenylphosphine with iron(ii) porphyrin. [M(TPP)]X (M=Mn, X = OAc M=Fe, X=C1 M = Co, X=Br) catalyses the epoxidation of styrene and cyclohexene with NaOCl under phase-transfer conditions. ... 

A Ru(TPFPP)(CO) (4) complex has been prepared, and it was found that 4 is an ef ficient catalyst for the aerobic oxidation of alkanes using acetaldehyde [110], Thus, the 4-catalyzed oxidation of cyclohexane with molecular oxygen in the presence of acetaldehyde gave cyclohexanone and cyclohexanol in 62% yields, based on acetaldehyde with high turnover numbers of 14 100 [Eq. (74)]. It is worth noting that iron... 

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