Diols reaction with cyclohexanone

The cycloalkylidene acetals are formed in essentially the same way as their iso-propylidene counterparts. Thus reaction of a diol with cyclopentanone [Scheme 3.42]M or cyclohexanone, usually with provision for the removal of water, accomplishes the transformation in good yield In the double protection of mannitol [Scheme 3.43], triethyl orthoformate served as the dehydrating agent and trifluoroborane etherate was the acid catalyst 65... 

The reaction with the acetal (1) gave cyclohexanone and benzoin (64% yield). This result and others suggested that the reaction would be useful for oxidation of a diol as... 

Acetal and ketal formation from aldehydes, resp. ketones and alcohols occurs over mordenite and other acidic zeolites [91] slightly above ambient temperatures in the liquid phase. The reaction is not confined to simple alcohols, diols can also be converted (e.g., cyclohexanone reacts with ethylglycol to 1,4, dioxaspiro(4,5)decane [2]). Note that it is likely that desorption controls the rate of such reactions as the product molecules are larger than the reactants and have, hence, a higher adsorption constant. 

Cyclohexylidene derivatives of 1,2-diob. Whereas 1,2-diols had traditionally been characterized by reaction with acetone to produce the acetonide or isopropylidene derivatives, Micovic and Stojiljkovic recommended conversion of sugars and other polyols into their cyclohexylidene derivatives because of the ease with which these substances crystallize. Angyal et al. explored the behavior of inositol (1) and found that this cyclitol gradually dissolved in a mixture of cyclohexanone and benzene containing p-toluenesulfonic acid on boiling under a Dean-Stark water separator. 

Butane-2,3-diol undergoes a reaction with ketones to form a ketal derivative as shown in Figure 50.12. The absolute configurations of acyclic ketones, cyclopentanones, and cyclohexanones with a preference for the chair conformation can be assigned based on an examination of the NMR spectra of the ketal derivatives. Butane-2,3-thiol can be used in the same manner and gives larger enantio meric discrimination, but it is not commercially available. 

The preparation of Pans-1,2-cyclohexanediol by oxidation of cyclohexene with peroxyformic acid and subsequent hydrolysis of the diol monoformate has been described, and other methods for the preparation of both cis- and trans-l,2-cyclohexanediols were cited. Subsequently the trans diol has been prepared by oxidation of cyclohexene with various peroxy acids, with hydrogen peroxide and selenium dioxide, and with iodine and silver acetate by the Prevost reaction. Alternative methods for preparing the trans isomer are hydroboration of various enol derivatives of cyclohexanone and reduction of Pans-2-cyclohexen-l-ol epoxide with lithium aluminum hydride. cis-1,2-Cyclohexanediol has been prepared by cis hydroxylation of cyclohexene with various reagents or catalysts derived from osmium tetroxide, by solvolysis of Pans-2-halocyclohexanol esters in a manner similar to the Woodward-Prevost reaction, by reduction of cis-2-cyclohexen-l-ol epoxide with lithium aluminum hydride, and by oxymercuration of 2-cyclohexen-l-ol with mercury(II) trifluoro-acetate in the presence of ehloral and subsequent reduction. ... 

An unusual reaction was been observed in the reaction of old yellow enzyme with a,(3-unsat-urated ketones. A dismutation took place under aerobic or anaerobic conditions, with the formation from cyclohex-l-keto-2-ene of the corresponding phenol and cyclohexanone, and an analogous reaction from representative cyclodec-3-keto-4-enes—putatively by hydride-ion transfer (Vaz et al. 1995). Reduction of the double bond in a,p-unsaturated ketones has been observed, and the enone reductases from Saccharomyces cerevisiae have been purified and characterized. They are able to carry out reduction of the C=C bonds in aliphatic aldehydes and ketones, and ring double bonds in cyclohexenones (Wanner and Tressel 1998). Reductions of steroid l,4-diene-3-ones can be mediated by the related old yellow enzyme and pentaerythritol tetranitrate reductase, for example, androsta-A -3,17-dione to androsta-A -3,17-dione (Vaz etal. 1995) and prednisone to pregna-A -17a, 20-diol-3,ll,20-trione (Barna et al. 2001) respectively. 

Hydroxy-4b/ -methyI-7-ethylenedioxy-l,2,3,4,4aa, 4b/ , 5,6,7,8,10,10a/ -dodecahydrophenanthren-l-one.184 To a solution of 2 g (6.9 mmoles) of 4b/ -methyl-7-ethylenedioxy-1,2,3,4,4aa, 4b) ,5,6,7,8,10,1 Oaa-dodecahydro-phenanthrene-1 / ,4/ -diol in 50 ml (0.48 mole) of cyclohexanone and 45 ml of anhydrous benzene is added a solution of 2 g (9.7 mmoles) of freshly distilled aluminum isopropoxide in 5 ml of benzene. The mixture is heated at reflux for 16 hr. After cooling the reaction mixture is treated dropwise with 4 ml of water. The precipitated aluminum salts are collected by filtration and thoroughly washed with benzene. The filtrate is concentrated initially at aspirator pressure, then finally at 0.1 mm at 135-140° to leave a crystalline residue. The residue is triturated with petroleum ether-ether (1 1) and filtered. After washing with the same solvent, the residue is recrystallized from acetone to give 1.35 g of 4/ -hydroxy-4b/ -methyl-7-ethylenedioxy-l,2,3,4,4aa,4b/ ,5, 6,7,8,10,10aa-dodecahydrophenanthren-l-one mp 218-219.5° (68%). 

Palladium-catalyzed reaction of allylic 1,1-diol diacetate 136 with the pyrrolidino enamine of cyclohexanone (137) yields 2-acetoxybicyclo[3.3.1]nonan-9-one (138)68 (equation 25). 

Nucleophilic addition of an alcohol to the carbonyl group initially yields a hydroxy ether called a hemiacetal, analogous to the gem diol formed by addition of water (Section 19.6). Hemiacetals are formed reversibly, with the equilibrium normally favoring the carbonyl compound. In the presence of acid, however, a further reaction can occur. Protonation of the -OH group followed by an El-like loss of water leads to an oxonium ion, R2C=OR, which undergoes a second nucleophilic addition of alcohol to yield the acetal. For example, reaction of cyclohexanone with methanol yields the dimethyl acetal. The mechanism is shown in Figure 19.12 (p. 778). 

The reagent has also been used for the synthesis of acetylenic diols.4 Thus 3-methyl-l-butyne-3-ol (6) is heated with two moles of the reagent to form the dilithio derivative. Cyclohexanone is added and the diol (7) is obtained in 60% yield. The reaction can also be carried out with acetylene and two different ketones. 

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