Cyclohexanol from cyclohexene oxide

The reaction of (1) with cyclohexene oxide produces the trans-cyclohexanol derivative (6). Acetylation of (6) followed by mercuric ion-promoted hydrolysis afforded the acetoxy aldehyde (7) in 82% overall from cyclohexene oxide. 

Cyclohexene oxide was first prepared by Brunei from o-iodo-cyclohexanol and solid potassium hydroxide.1 It has also been obtained by the oxidation of cyclohexene with benzoyl hydroperoxide.2... 

Of special interest for petrochemical and organic synthesis is the implementation of thermodynamically hindered reactions, among which incomplete benzene hydrogenation or incomplete cyclohexene and cyclohexadiene dehydrogenation should be mentioned. Cost-effective methods of cyclohexene production would stimulate the creation of new processes of phenol, cyclohexanol, cyclohexene oxide, pyrocatechol synthesis, cyclohexadiene application in synthetic rubber production, and a possibility for designing caprolactam synthesis from cyclohexene and cyclohexadiene via combined epoxidation. At present, the most... 

Iron(III) weso-tetraphenylporphyrin chloride [Fe(TPP)Cl] will induce the autoxidation of cyclohexene at atmospheric pressure and room temperature via a free radical chain process.210 The iron-bridged dimer [Fe(TPP)]2 0 is apparently the catalytic species since it is formed rapidly from Fe(TPP)Cl after the 2-3 hr induction period. In a separate study, cyclohexene hydroperoxide was found to be catalytically decomposed by Fe(TPP)Cl to cyclohexanol, cyclohexanone, and cyclohexene oxide in yields comparable to those obtained in the direct autoxidation of cyclohexene. However, [Fe(TPP)] 20 is not formed in the hydroperoxide reaction. Furthermore, the catalytic decomposition of the hydroperoxide by Fe(TPP)Cl did not initiate the autoxidation of cyclohexene since the autoxidation still had a 2-3 hr induction period. Inhibitors such as 4-tert-butylcatechol quenched the autoxidation but had no effect on the decom-... 

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). 

Whatever the mechanism of sulfoxide reduction, oxidized solvent molecules were observed in the photolysis of 9. For example, benzene is converted to phenol, cyclohexane to cyclohexene and cyclohexanol, and cyclohexene to cyclohexene oxide and 2-cyclohexenol [99]. Oxygen atom accounting ranges from fairly poor (ca. 1/3) to quantitative, depending on the solvent substrate. The stepwise and fairly selective nature of the oxidizing agent are suggested by... 

The presence of ascorbic acid as a co-substrate enhanced the rate of the Ru(EDTA)-catalyzed autoxidation in the order cyclohexane < cyclohexanol < cyclohexene (148). The reactions were always first-order in [H2A]. It was concluded that these reactions occur via a Ru(EDTA)(H2A)(S)(02) adduct, in which ascorbic acid promotes the cleavage of the 02 unit and, as a consequence, O-transfer to the substrate. While the model seems to be consistent with the experimental observations, it leaves open some very intriguing questions. According to earlier results from the same laboratory (24,25), the Ru(EDTA) catalyzed autoxidation of ascorbic acid occurs at a comparable or even a faster rate than the reactions listed in Table III. It follows, that the interference from this side reaction should not be neglected in the detailed kinetic model, in particular because ascorbic acid may be completely consumed before the oxidation of the other substrate takes place. 

No atoms are lost in the cleavage reaction so that cheap cyclohexene 6 is used to make adipic acid 7 for nylon manufacture. Any of the oxidative cleavage methods from the last chapter could be used Vogel1 has a recipe using concentrated nitric acid on cyclohexanol 8 that presumably goes by dehydration to the alkene 6 followed by oxidation, and other methods are probably used industrially. 

Caprolactam (world production of which is about 5 million tons) is mostly produced from benzene through three intermediates cyclohexane, cyclohexanone and cyclohexanone oxime. Cyclohexanone is mainly produced by oxidation of cyclohexane with air, but a small part of it is obtained by hydrogenation of phenol. It can be also produced through selective hydrogenation of benzene to cyclohexene, subsequent hydration of cyclohexene and dehydrogenation of cyclohexanol. The route via cyclohexene has been commercialized by the Asahi Chemical Company in Japan for adipic acid manufacturing, but the process has not yet been applied for caprolactam production. 

The controlled oxidation of alkanes into alcohols also attracts attention from an industrial point of view. Copper-based catalysts containing Tp ligands have been employed as catalysts for this reaction that led to a very interesting as well as unprecedented transformation with copper. Thus, when cyclohexane was reacted with in the presence of these catalysts, cyclohexane was partially converted into cyclohexanol and cyclohexanone, as expected. However, a certain amount of cyclohexane underwent dehydrogenation affording cyclohexene, in the first example of a copper-mediated alkane dehydrogenation process. Part of the cyclohexene was epoxidized in the reaction... 

Photoionization of the hydrocarbon followed by dissociative electron attachment (Reaction 1) should be considered since the ionization potential of a molecule is less in the liquid phase than it is in the gas phase. For hydrocarbons the ionization potential is 1 to 1.5 e.v. less in the liquid phase (24). The photon energy at 1470 A. is about 1.4 e.v. below the gas-phase ionization potentials of cyclohexane and 2,2,4-trimethylpentane (14). Some ionization may therefore occur, but the efficiency of this process is expected to be low. Photoionization is eliminated as a source of N2 for the following reasons. (1) If photoionization occurred and the electron reacted with nitrous oxide, then O" would be formed. It has been shown in the radiolysis of cyclohexane-nitrous oxide solutions that subsequent reactions of O result in the formation of cyclohexene and dicyclohexyl (I, 16, 17) and very little cyclohexanol (16, Table III). In the photolysis nitrous oxide reduces the yield of cyclohexene and does not affect the yield of dicyclohexyl. This indicates that O is not formed in the photolysis, and consequently N2 does not result from electron capture. (2) A further argument against photoionization is that cyclohexane and 2,2,4-trimethylpentane have comparable gas-phase ionization potentials but exhibit quite different behavior with respect to N2 formation. 

Cyclohexene will undergo an ozonolysis reaction to yield adipic acid upon oxidative workup. Cyclohexene is produced from cyclohexanol by a dehydration (elimination) reaction. The synthesis of adipic acid from cyclohexanol is... 

A very important application of zeolites includes in the hydration/dehy-dration reactions. A very interesting example is the Asahi process for the hydration of cyclohexene to cyclohexanol over a high silica (Si/Al>20), H-ZSM-5 type catalyst [44]. The process has been operated successfully on a 60,000 tons per year since 1990. However, this process has a problem of catalyst deactivation. The hydration of cyclohexanene is a key step in an alternative route to cyclohexanone (and phenol) from benzene (Figure 11.11). The conventional route involves hydrogenation of cyclohexane followed by auto-oxidation to a mixture of cyclohexanol and cyclohexanone and subsequent dehydrogenation of the former. A disadvantage of this process is only 75-80% selectivity at very low conversions (ca. 5%), thus one has to the recycle of enormous quantities of cyclohexane. 

Other rare earth elements ako found activity in these catalysts. The catalytic activity of cerium-incorporated cage-type mesoporous KlT-6 materials in oxidation of cyclohexene was explained as effect of from the framework with tetrahedral oxidic coordination [27]. When H2O2 is chemisorbed, only the distant oxygen is activated, by which cyclohexane could be oxidized by insertion of oxygen across the C—H bond, as illustrated in Scheme 21.1. Hence, cyclohexanol is the principal product in thk oxidation. Recyclability of the catalyst without leaching of cerium in the presence of the solvent was an important characteristic of this catalyst. Acetic acid as a solvent led to better results compared to either acetone or methanol. 

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