1.2- Diols from aromatic compounds

Enantiopure epoxides and vicinal diols are important versatile chiral building blocks for pharmaceuticals (Hanson, 1991). Their preparation has much in common and they may also be converted into one another. These chirons may be obtained both by asymmetric synthesis and resolution of racemic mixtures. When planning a synthetic strategy both enzymic and non-enzymic methods have to be taken into account. In recent years there has been considerable advance in non-enzymic methods as mentioned in part 2.1.1. Formation of epoxides and vicinal diols from aromatics is important for the break down of benzene compounds in nature (See part 2.6.5). 

Clever entries to enantiopure carbapyranoses exploited optically pure or meso cw-diene diols easily obtained from aromatic compounds by... 

The metabolic oxidation of otefinic carbon-carbon double bonds leads to the corresponding epoxide (or oxiranc). Epoxides derived from olefins generally tend to be somewhat more stable than the arene oxides formed from aromatic-compounds. A few epoxides arc stable enough to be direclly mcasurable in biological fluids (e.g.. plasma, urine). Like their arene oxide counterparts, epoxides- are susceptible to cnz.ymatic hydration by epoxide hydra.se to form lran,s-. 2-dihydrodiols (al.so called 1,2-diols or 1.2-dihydroxy com-... 

Abstract This chapter describes the production of cis-3,5-cyclohexadiene-l,2-diol (DHCD) from aromatic compounds, their polymerization into poly(p-phenyelene) (or PPP), and the properties and applications of the polymer. Large-scale synthesis of DHCD has been demonstrated, and DHCD is widely used in the pharmaceutical industry, as well as in chemical industries for polymer productions. Recent study including different types of dioxygenases, strain development by recombination, and genetical modification were done to develop the process technology for commercialization of this new polymer and chemical intermediates. 

Sequences of proteins containing Rieske-type clusters have been deduced from the complete operons of several dioxygenases these dioxygenases require electrons from NAD(P)H to convert aromatic compounds to cis-arene diols. The water-soluble dioxygenase systems consist of a reductase and a terminal dioxygenase many dioxygenases also contain a [2Fe-2S] ferredoxin (20). The terminal oxygenases contain a Rieske-type cluster and the ferredoxins may contain either a Rieske-type or a 4-cysteine coordinated [2Fe-2S] cluster. 

An alternative is FGI back to the ketone 67 and hence the a-bromoketone 68 that can be made from the ketone 69 itself by methods discussed earlier in this chapter. The ketone 69 is clearly made by some sort of Friedel-Crafts acylation, but how are we to make the diol 70 In chapter 3 we said that a good strategy to make ort/io-disubstituted aromatic compounds was to start with an... 

Dihydroxynaphthalene and 9,10-diacetoxyphenanthrene react with 1,2-diols and 1,2-dithiols in a one-pot synthesis of annulated 2,3-dihydro-1,4-dioxins and -1,4-dithiins (Scheme 26) <04TL1343>. The reaction of 2,3-dihydroxynaphthalene with 1,2-dihalogenated aromatic compounds leads to linearly annulated dioxins of particular interest are tri- and tetra-dioxins and various hetero-fused dioxins e.g. 62 (34%). Several examples yield cation radical salts on electrocrystallisation <04T8899>. Linear arrays of fused pyran-dioxin-cyclohexane rings as found in natural products derived from the milkweed family have been described e.g. 63 <04EJO4911>. 

The pioneering work of Gibson3 on the isolation and mutation of Pseudomonas strains that oxidatively degrade aromatic compounds has led, 25 years later, to the application of cyclohexadiene cis-diols in asymmetric synthesis. The first applications of these types of compounds to synthesis were the use of meso-diol derived from benzene for production of polyphenylene4 by ICI and in the synthesis of racemic... 

The use of 284-287 as well as other diol derivatives derived from functionalized aromatic compounds is clearly an important method for the preparation of molecules that can be used in asymmetric synthesis. This process provides an important source of diol starting materials that can be manipulated to form a variety of important natural products. This interesting oxidation leads to the functional group transform ... 

Contrary to some reports, electrophilic addition reactions may occur in other multiple-bond systems. In many of the reactions of aldehydes and ketones the first stage involves the addition of some entity across the carbon-oxygen bond, e.g., the formation of oximes, semicarbazones, hydrazones, hydrates (1,1-diols) and their ethers, and the aldol condensation. Most of these reactions entail a subsequent loss (elimination) of a small molecule e.g. water, ammonia, ethanol) and, while one must be careful to determine whether the rate-determining stage involves attack on the carbonyl compound or elimination from the adduct , there are some systems in which it is evident that electrophilic attack is involved in the slow stage of the reaction sequence. Examples of such reactions are the acid-catalysed formation of oximes of aliphatic - and aromatic carbonyl compounds, of furfural semi-carbazone , and of 1,1-diols from aldehydes or ketones . 

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