Diols, as intermediates

The method ZC3Z + C is used for the preparation of reduced pyrimidines, oxazines and thiazines as well as for dioxanes, dithianes and oxathianes as mentioned above (e.g. 258 — 257, 259 Z, Z = NH, O, S). The Prins reaction yields 1,3-dioxanes (77S661) it involves the acid-catalyzed condensation of alkenes with aldehydes with 1,3-diols as intermediates. 

Sodium periodate (sodium metaperiodate), NaI04 (mp 300 °C dec), which is commercially available, is applied mainly in aqueous or aqueous-alcoholic solutions. Like the free periodic acid, sodium periodate cleaves vicinal diols to carbonyl compounds [762], This reaction is especially useful in connection with potassium permanganate [763, 764] or osmium tetroxide [765], Such mixed oxidants oxidize alkenes to carbonyl compounds or carboxylic acids, evidently by way of vicinal diols as intermediates. Sulfides are transformed by sodium periodate into sulfoxides [322, 323, 766, 767, 768, 769, 770, 771, 772], and selenides are converted into selenoxides [773]. Sodium periodate is also a reoxidant of lower valency ruthenium in oxidations with ruthenium tetroxide [567, 774],... 

Whited, G.M., W.R. McCombie, L.D. Kwart, and D.T. Gibson. 1986. Identificaton of c/s-diols as intermediates in the oxidation of aromatic acids by a strain of Pseudomonas putida that contains a TOL plasmid.. Bacteriol. 166 1028-1039. 

Another pathway that is believed to exist involves the formation of 7a-hydroxy-5jS-cholestene-3-one and 5j5-cholestene-3a, 7a-diol as intermediates. The importance of the pathway is not known. 

Cyclohexadiene-d.s -diols as versatile intermediates in the synthesis of natural heterocycles 96CC1993. 

This reachon, of industrial interest, utilizes singlet oxygen generated by irradiation in the presence of Rose Bengal [40]. An endoperoxide is formed as intermediate which is converted to 2-cyclopentene-l,4-diol by reduchon with thiourea. 

As reductions by metals often occur by one-electron transfers, radicals are involved as intermediates. When the reaction conditions are adjusted so that coupling competes favorably with other processes, the formation of a carbon-carbon bond can occur. The reductive coupling of acetone to 2,3-dimethylbutane-2,3-diol (pinacol) is an example of such a reaction. 

In a similar manner, and as shown again by the Faber group, the catalyzed reaction of bis-epoxides led to THFs containing four stereocenters [22]. Thus, treatment of cis,ds,weso-8-51 with the epoxide hydrolase Rhodococcus sp. CBS 71773 predominantly yielded the THF derivative 8-53a in 94% ee and 89% de, whereas the use of other biocatalysts has shown only low to moderate stereoselectivity (Scheme 8.14). As intermediate, the diol 8-52 can be assumed, whereby for the further transformation path A is always favored. 

The glutathione 5-transferase pathway is sometimes in biochemical competition with the epoxide hydratase pathway, in that both deactivate intermediates of the MMFO. Epoxide hydratase is a microsomal enzyme that acts specifically to deactivate epoxide intermediates, by the addition of water across the C—O bond to form a diol. As a very broad generality, the glutathione 5-transferase pathway tends to be more prominent in rodents, while the epoxide hydratase pathway tends to be more dominant in nonrodents. 

Phenylacetyl chloride and hydrocin-namoyl chloride are reduced at mercury to form both acyl radicals and acyl anions as intermediates [76]. From electrolyses of phenylacetyl chloride, the products include 1,4-diphenyl-2-butene-2,3-diol diphenylac-etate, phenylacetaldehyde, toluene, 1,3-diphenylacetone, and l,4-diphenyl-2,3-butanediol, and analogous species arise from the reduction of hydrocinnamoyl chloride. Reduction of phthaloyl dichloride is a more complicated system [77] the electrolysis products are phthalide, biph-thalyl, and 3-chlorophthalide, but the latter compound undergoes further reduction to give phthalide, biphthalyl, and dihydrobi-phthalide. 

Of equally high industrial potential as intermediate chemicals are the various HMF-derived products for which well-worked-out, large-scale adaptable production protocols are available. Of these, the 5-hydroxymethyl-furoic acid, the 2,5-dicar-boxylic acid, the 1,6-diamine, and the respective 1,6-diol (framed in Scheme 2.12) are the most versatile intermediate chemicals of high industrial potential, as they represent six-earbon monomers that could replace adipic acid, alkyldiols, or hexamethy-lenediamine in the production of polyamides and polyesters. 

Incubation of the (1R,2R) diol 25 over a shorter time period of 4 days gave a mixture of the meso cis diol 26 (26%) and the trans diol 25 RR/SS 76 26) showing conversion over to the (1S,2S) diol. As with the previous examples, no conversion was observed when using the S,S diol 25 as a substrate. Although no intermediate a-hydroxyketone was observed for this substrate we proposed the operation of at least two dehydrogenase enzymes, DH-1 and DH-2, catalysing the (i )-selective oxidation and (S)-selective reduction respectively (Scheme 12). Incubation of cis cycloheptan-l,2-diol afforded only the (S)-2-... 

Obviously with the indan-l,2-diol substrates there is no symmetrical meso intermediate which makes interpretation of the mechanism more difficult. In both the cyclohexan-l,2-diol and the indan-l,2-diol series the trans diols react faster and cis diols (both enantiomers for indandiol) are seen as intermediates. The (IS,2R) cis indandiol 29 is faster reacting and on incubation of the racemate only a very small trace of the R,R)-trans 28 isomer is observed. 2-Hydroxyin-dan-1 -one 30, an observed intermediate in these biotransformations, undergoes kinetic resolution when incubated as a racemic substrate. The faster reacting enantiomer is reduced to the faster reacting cis (lS,2i )-indan-l,2-diol 29 which is subsequently transformed into both trans diols and ultimately the (S,S)-iso-mer. Current work is focussing on determining the absolute configuration of the intermediate a-hydroxyketone 30. 

If a diol is oxidatively dehydrogenated to form a diacid via an intermediate with one Off group, then a first order plot based on hydrogen evolution can exhibit some curvature. This is because the slope at any time will reflect the instantaneous concentrations of the diol and intermediate as well as their intrinsic reactivities. First order plots for the reaction of ethylene glycol, 1,4-butanediol and diethanolamine are shown in Figure 2. All plots are reasonably linear, consistent with reaction via an intermediate with a rate constant rather similar to that of the starting diol (or a direct reaction with no intermediate whatsoever). 

Oxidation to Arene Oxides and Arene Diols. Arene oxides and arene diols have been widely studied particularly concerning the metabolism of polycyclic aromatic compounds and their implication as intermediates responsible for the carcinogenicity and mutagenicity of polycyclic aromatic hydrocarbons.803,804... 

There have been a few reports of aerobic bacterial species which will grow on dibenzothiophene as their sole carbon source (51,52)- However, most studies have focused on its co-metabolism (22,52,54) which appears to be a more common phenomenon. Intermediates of the biodegradation have been identified in a number of studies (55-57). Figure 10 is a simplification of the proposed pathway for dibenzothiophene metabolism showing the two endproducts 3-hydroxy-2-formylbenzothiophene (HFBT), which is the more abundant, and dibenzothiophene-sulfoxide. [For a more complete pathway see (56) or (58)1. This pathway shows 1,2-dihydroxydibenzothiophene as an intermediate and this is analogous to the diols found as intermediates of aromatic hydrocarbons. 

Kasai, and K. Nakanishi. Benzo(a)pyrene diol epoxides as intermediates in nucleic acid binding in vitro and in vivo. Science 193 592-595, 1976. 

The possibility cannot be excluded that the cis-vic dihydroxylation of alkenes with 0s04 in the presence of water proceeds via intermediate D and perhaps even via E. Hydrolysis of either of these species would namely yield the same diol as the hydrolysis of B. 

Most compounds of this type are cyclic sulfite and sulfate esters of aromatic 1,2-diols as well as anhydrides of aromatic 1,2-disulfonic acids. The simplest representatives with unsubstituted benzene rings are 1,3,2-benzodioxathiole 2-oxide (48) (catechol sulfite), the corresponding 2,2-dioxide (156) (catechol sulfate) and 2,1,3-benzoxadithiole 1,1,3,3-tetroxide (158) (1,2-benzenedisulfonic anhydride). Compound (48) was synthesized by refluxing catechol with thionyl chloride in the presence of pyridine. In a similar fashion, from 2-mercaptophenol 1,2,3-benzoxadithiole 2-oxide was prepared (81AG603). The dioxide (156) was obtained in two steps by reaction of catechol monosodium salt with sulfuryl chloride in benzene at 0-10 °C and subsequent reflux of the intermediate (155) in the presence of pyridine. 

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