Cyclohexanols synthesis

Cycloheptatrienes, synthesis of 801 Cyclohexadienes 800, 801 Cyclohexanols, synthesis of 838 Cyclopentanones, naturally occurring 321 Cyclopentanone sulphoxides, reactions of 341... 

Fig. 5.21. Chemical equilibrium curves for the cyclohexanol synthesis at p — 0.1 MPa ([19], reprinted from Chem. Eng. Sci., Vol 57, Qi, Kolah and Sund-macher. Pages 163-178, Copyright 2002, A/ith permission from Elsevier Science)...

Recently, Steyer et al. [22] presented an extended analysis of cyclohexanol synthesis and splitting, supposing that the chemical reaction will proceed in the two liquid phases at different rates, that is with different Damkbhler numbers. Based on their results, these authors proposed a flow-sheet of two coupled RD columns for the separation of cyclohexene/cyclohexane mixtures. 

Recognizing that cyclohexene may be prepared by dehydration of cyclohexanol a prac tical synthesis of cyclohexane from cyclohexanol becomes apparent... 

The constitution of carvestrene has been determined, subject to the limitation above referred to as to the constitution of isocarvestrene, by the masterly synthesis achieved by W. H Perkin, Jr., and his colleagues. The starting-point of this synthesis was t-hydroxy-benzoic acid, which was reduced by sodium and alcohol to cyclohexanol-3-carboxylic acid, of the formula—... 

Br(OAc)J Oxidations of Alcohols Investigated in Micro Reactors Organic synthesis 83 [OS 83] Br(OAc)J Oxidation of cyclohexanol... 

Figure 7.14 Biocatalytic and chemical synthesis of (I ff,2.S )-2-methy 1-1-cyclohexanol...

A" 0-Butenolide, 46, 22 /-Butyl alcohol, in synthesis of phenyl /-butyl ether, 45, 89 reaction with sodium cyanate and trifluoroacetic acid, 48, 32 /-Butyl azidoacctatc, 46, 47 hydrogenation of, 45, 47 /-Butyl carbamate, 48,32 /-Butyl chloroacetate, reaction with sodium azide, 45, 47 /ra S-4-/-BuTYI,CYCLOHEXANOL, 47,16... 

Other mediators which have been used in combination with diaphorase for the regeneration of NAD+ are riboflavin and Vitamin K3, which is 2,3-dimethyl-1,4-naphthoquinone. However, especially riboflavin is not stable enough for synthetic applications [40]. Better stability is exhibited by phenanthrolindiones as mediators. In combination with diaphorase, Ohshiro [41] showed the indirect electrochemical oxidation of cyclohexanol to cyclohexanone using the NAD+ dependent HLADH with a turnover frequency of two per hour. For an effective enzymatic synthesis, this turnover frequency, however, would be too small. In our own studies, we were able to accelerate the NAD(P)+ regeneration considerably by lowering the electron density within the... 

Pentacene can be efficiently prepared by reduction of pentacenequinone by an aluminium-cyclohexanol mixture (Goodings et al, 1972). A scheme of this synthesis is shown in Fig. 2.1. Other synthetic routes with good overall yields have also been reported. 

Figure 3.3 shows a simple example of a retrosynthetic synthesis of cyclohexanol. Cyclohexanol may be disconnected to a hydride ion and a hydroxycarbocation (the synthons). Sodium borohydride and cyclohexanone are the synthetic equivalents of these two synthons. Thus, reacting cyclohexanone with NaBH will produce cyclohexanol. 

The same authors 83) used the chiral ketone (46) as substrate for the preparation of optically active cyclohexanol derivatives (47) which may be useful intermediates in the synthesis of chiral natural products, such as (—)-mesenbranoene, (+)-2-carene etc. 

The discovery of 1 -aryl-1 -dimethylamino-cyclohexanes resulted from a surrey of compounds in which aromatic and basic features, both critical structural requirements of opioid analgesics, but usually separated by two or three carbon atoms, are linked to the same quaternary carbon. The synthesis of these compounds yielded a series of highly potent opioids (e.g. 1-Benzyl-4-(4-bromo-phenyl)-4-dimethylamino-cyclohexanol), however none of them are in clinical use (Lednicer et al., 1981). 

Oxidation of Cyclohexane. The synthesis of cyclohexanol and cyclohexanone is the first step in the transformation of cyclohexane to adipic acid, an important compound in the manufacture of fibers and plastics. Cyclohexane is oxidized industrially by air in the liquid phase to a mixture of cyclohexanol and cyclohexanone.866 872-877 Cobalt salts (naphthenate, oleate, stearate) produce mainly cyclohexanone at about 100°C and 10 atm. The conversion is limited to about 10% to avoid further oxidation by controlling the oxygen content of the reaction mixture. Combined yields of cyclohexanol and cyclohexanone are about 60-70%. 

Using air, the oxidation of hydrocarbons generally results in a mixture of oxygenated compounds and is not a useful synthesis of alcohols except under special circumstances. Cyclohexanol may be prepared by air oxidatron of cydohexane inasmuch as only one isomer can result. 

BARDHAN-SENGUPTA SYNTHESIS. Phosphorus pentoxide and other powerful dehydrating agents act upon 2-beta-phenethyl-l-cyclohexanol to form oclahydrophenanlhrene compounds. 

Homolytic liquid-phase processes are generally well suited to the synthesis of carboxylic acids, viz. acetic, benzoic or terephthalic acids which are resistant to further oxidation. These processes operate at high temperature (150-250°C) and generally use soluble cobalt or manganese salts as the main catalyst components. High conversions and selectivities are usually obtained with methyl-substituted aromatic hydrocarbons such as toluene and xylenes.95,96 The cobalt-catalyzed oxidation of cyclohexane by air to a cyclohexanol-cyclohexanone mixture is a very important industrial process since these products are intermediates in the manufacture of adipic acid (for nylon 6,6) and caprolactam (nylon 6). However, the conversion is limited to ca. 10% in order to prevent consecutive oxidations, with roughly 70% selectivity.97... 

Adipic acid is a most important petrochemical product which is mostly used for the synthesis of nylon 6.6 from its condensation with hexamethylenediamine. Cyclohexane is transformed to adipic acid in two steps (a) oxidation of cyclohexane to a cyclohexanol-cyclohexanone mixture (ol-one) via the formation of cyclohexyl hydroperoxide followed by (b) oxidation of the ol-one mixture to adipic acid by nitric acid (equation 239). 

Let s look at a very simple one-step synthesis to illustrate this difference. Given die following set of reactants, methyl cyclohexanol and chromic acid in acetone, it is very easy to write the product as 4-methylcyclohexanone ... 

Shine and co-workers239,240 have reported the synthesis and full NMR characterization of a series of alkoxysulfonium ion perchlorates including ions 85 derived from cis- and fraws-substituted cyclohexanols. The X-ray structural study of four salts showed that the orientation of the S O bond is always pseudoaxial. The optically active (—)-86 ion and similar systems have been synthesized.241 1H and 13C NMR measurements indicate that sulfur has a trigonal bipyramidal geometry due to the S—O intramolecular interaction in the axial position. 

The oxidation of cyclohexane to cyclohexanone and cyclohexanol is an important industrial procedure used in the synthesis of adipic acid. Srinivas and Mukhopadhyay (1994) reported the oxidation of cyclohexane in sc C02, yielding cyclohexanone and cyclohexanol as the major reaction products. At the high temperatures employed in this study (>137°C), cyclohexyl hydroperoxide (c-C6HnOOH), which is produced by the mechanism outlined in Scheme 4.11, decomposes to cyclohexanone and cyclohexanol. 

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... 

Cyclohexane, the six-carbon ring hydrocarbon with the molecular formula C6H12, is the most significant of the cyclic alkanes. Under ambient conditions it is a clear, volatile, highly flammable liquid. It is manufactured by the hydrogenation of benzene and is used primarily as a raw material for the synthesis of cyclohexanol and cyclohexanone through a liquid-phase oxidation with air in the presence of a dissolved cobalt catalyst. 

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