Cyclohexane Diols

Cyclopentene-l-carboxaldehydes are obtained from cyclohexene precursors by the sequence cyclohexene - cyclohexane-1,2-diol -> open-chain dialdehyde - cyclopentane aldol. The main advantage of this ring contraction procedure is, that the regio-and stereoselectivity of the Diels-Alder synthesis of cyclohexene derivatives can be transferred to cyclopentane synthesis (G. Stork, 1953 G. BUchi, 1968). 

Cyclohexadiene has been prepared by dehydration of cyclohexen-3-ol,3 by pyrolysis at 540° of the diacetate of cyclohexane-1,2-diol,4 by dehydrobromination with quinoline of 3-hromocyclohexene,6 by treating the ethyl ether of cyclohexen-3-ol with potassium bisulfatc,6 7 by heating cyclohexene oxide with phthalic anhydride,8 by treating cyclohexane-1,2-diol with concentrated sulfuric acid,9 by treatment of 1,2-dibromocyclo-hexane with tributylamine,10 with sodium hydroxide in ethylene glycol,10 and with quinoline,6 and by treatment of 3,6-dibromo-cyclohexene with sodium.6... 

Retardation by acetic acid itself, which reduces the oxidation rate of trans-cyclohexane-1 2-diol by three orders of magnitude, suggests the existence of a pre-equilibrium... 

Cyclohexene oxide (1,2-epoxycyclohexane, 10.5, Fig. 10.29) has received particular attention as a substrate for EH (see Table 10.1). The compound has a meso-cis geometry like d.v-stilbcnc oxide (10.7), and, like the latter, is hydrated preferentially to the chiral (/ ,/ )-/ran.y-cyclohexane-1,2-diol (10.124) [185], There was a difference, however, between the activities of the rabbit liver microsomal and cytosolic EHs. The former was ca. 20-fold more active than the latter toward this substrate also, it formed the (R,R)-diol with 94% enantiomeric excess (ee) compared to only 22% ee for the cytosolic EH. 

Cyclohexene TlCl04/HCl04-(Pt) tI(cio4)3 Cyclopentane-1-carboxylic acid, Cyclohexanone, Cyclohexane-1,2-dione, Cyclohexane-1,2-diol 247... 

In 1999, Sanjuan and co-workers [27] reported a very elegant type IIavRH oxidation of cyclohexene to give a mixture of cyclohexane-1, 2-diol, 2-cyclohexenol, and 2-cyclohexenone. The reaction is initiated by excitation of the zeolite-embedded 2,4,6-triphenylpyrylium cation to produce a hydroxy radical (steps 1 and 2... 

In principle, a number of different types of acetal or ketal might be produced. In this section, we want to exemplify a small number of useful reactions in which two of the hydroxyl groups on the sugar are bound up by forming a cyclic acetal or ketal with a snitable aldehyde or ketone reagent. Aldehydes or ketones react with 1,2- or 1,3-diols under acidic conditions to form cyclic acetals or ketals. If the diol is itself cyclic, then the two hydroxyl groups need to be cA-oriented to allow the thermodynamically favourable fused-ring system to form (see Section 3.5.2). Thus, dx-cyclohexan-1,2-diol reacts with acetone to form a cyclic ketal, a 1,2-O-isopropylidene derivative usually termed, for convenience, an acetonide. 

By choosing an appropriate titanium complex, a /ra r-isomer of 1,2-cyclohexanols can be prepared selectively. Because intramolecular pinacol coupling of hexanedials with Sml2 usually produces t-isomers of cyclohexane-1,2-diols, the titanium-mediated reaction complements the samarium-mediated cyclization (Equation (17)). In addition, when a /-butyl group fixes the conformation of the substrate, one of the diastereomers is produced selectively (Equation (18)). ... 

R,R)- and (S -cyclohexanediamines 102 self-assemble with cyclohexane-1,2-diol 103 forming helical fibers of 40-70 nm length whilst the racemate produces platelets [53]. 

Cyclohexanediol and derivs 3 C595—C596 cyclohexane- 1,2-diol dinitrate 3 C596... 

Because organobismuth(V) compounds have found considerable use as oxidizing agents, the oxidizing ability of methyl di-l-naphthylbismuthinate [124066-66-6], C21H17Bi02, was investigated. Benzoin yields benzil, naphthalene, and metallic bismuth hydrazobenzene yields azobenzene, and 1,1,2,2-tetraphenylethanediol yields benzophenone. 1,2-Diphenyl-1,2-ethanedione dihydrazone gives diphenylacetylene in 50% yield. Cyclohexane-1,2-diol and 1-phenylethane-l,2-diol, however, were unaffected. 

J. S. Brimacombe, A. B. Foster, B. D. Jones, and J. J. Willard, Reaction of the cyclohexane-1,2-diols and methyl 4,6-0-benzylidene-a-D-gluco- and galactopyranoside with methylene halides, J. Chem. Soc. C. 2404 (1967). 

Exercise 11-16 Starting with cyclohexene, show how you could prepare each of the following compounds a. the epoxide of cyclohexene, b. c/s-cyclohexane-1,2-diol, and c. frans-cyclohexane-1,2-diol. 

Cyclohexane 1,2 - diol or 1,2 - Hexabydrocate-chol [called Cyclohexandiol - (1.2), Hexahydro-brenzcatechin or Brenzcatechit in Ger],... 

N 13.59%. Two mildly expl isomers were prepd by nitrating the corresponding diols cis-Cyclohexane - 1,2-diol Dinitrate, prismatic rods (from hot ligroin), mp 24.5 25°, nQ 1.4790 at 21° impact test value with 2 kg wt (Rotter machine) 60 cm vs 100 cm for TNT fumes at 170° Bergmann-Junk test 0.67 mg NO evolved/ lg sample in 20 hrs at 106°... 

A material prepared by anchoring titanium(IV) on to the walls of a high-area, crystalline mesoporous silica (MCM41) has been used as an alkene epoxidation catalyst with alkyl hydroperoxides.204 The effect of replacing one of the three O—Si= groups to which the Ti(IV) is bound by an O—Ge= group is reported to lead to an increase in catalytic activity of up to 18% in die epoxidation of cyclohexene, although no explanation is provided and it is notable diat the selectivity towards the formation of cyclohexene oxide (versus cyclohexenol and cyclohexane-1,2-diol) was inferior to that with the non-modified system.205... 

The aminolyses of the carbonates derived from cyclopentane-1,2-diol (38) and cyclohexane-1,2-diol (39) by hexylamine at 70 °C were much slower than that of ethylene carbonate, the latter (39) being about twice as reactive as the former (38). Computational calculations confirmed that ring strain was the main determining factor.40... 

Ruthenium(VI)-catalysed oxidation of propane-1,2-diol, cyclohexane-1,2-diol, and propanetriol by alkaline HCF(III) exhibits a zero-order dependence on HCF(III) and first-order dependence on Ru(VI) and the rate increased with a decrease in alkali concentration. The reaction showed a Michaelis-Menten type of behaviour with respect to the reductant. A tentative mechanism has been proposed.63 In the ruthenium(in)-catalysed oxidation of sulfanilic acid by HCF(III) in alkaline medium, the proposed ruthenium(III) active species is [Ru(H20)50H]2+.64 Iridium(III) chloride-catalysed oxidation of diethylene glycol by alkaline HCF(III) is proposed to proceed through complex formation.65... 

When refluxed in benzene, 3 undergoes dehydrocobaltation to provide the methyl ketone 4. When irradiated with a sunlamp at 25°, 3 cyclizes to a cyclohexane-1,2-diol (5) as a 3 2 mixture of isomers. A similar cyclization to a cyclopentanol is also possible. 

Figure 33. (a) and (c) cis-dihydroxylation of toluene to give enantiomeric diene-diols, and catalytic reduction to the corresponding cyclohexane-1,2-diols. (b) cYc "... 

The deracemization of rac-1-methyl-1,2-epoxycyclohexane (64) (Fig. 18.23) has been demonstrated by cells of Corynebacterium sp C12 and Methylobac-terium sp. (Archer et al., 1996 Ueberbacher et al., 2005). A one pot combination of Corynebacterium C12 epoxide hydrolase and acid catalysed ring opening converted rac-1-methyl-1,2-epoxycyclohexane to (1-S, 2-5)-1-methyl-cyclohexane-1,2-diol. Alternatively, instead of the chemical conversion of the unreacted oxirane, the formed diol can be converted into the remaining epoxide (Monfort et al., 2004). 

Alicyclic compounds, such as cyclohexane, are also susceptible to oxidation, in this case first to cyclohexanol and then to /rans-cyclohexane-1,2-diol, cyclohexaone, and adipic acid. 

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