Vicinal diol preparation

Figure 7.9. The mass spectrum of the trimethylsilyl ether derivative of the vicinal diol prepared from methyl...

In the laboratory vicinal diols are normally prepared from alkenes using the reagent osmium tetraoxide (OSO4) Osmium tetraoxide reacts rapidly with alkenes to give cyclic osmate esters... 

Steroidal cis vicinal diols at the 1,2-, ° 2,3-, ° 5,6- or 11,12- " positions can be selectively protected as acetonides, prepared by reaction with acetone at room temperature or at higher temperatures in the presence of hydrochloric, perchloric or -toluenesulfonic acids. Cis nonvicinal-diols can be similarly protected. 

By application of the Corey-Winter reaction,vicinal diols 1 can be converted into olefins 3. The key step is the cleavage of cyclic thionocarbonates 2 (1,3-dioxolanyl-2-thiones) upon treatment with trivalent phosphorus compounds. The required cyclic thionocarbonate 2 can be prepared from a 1,2-diol 1 and thio-phosgene 4 in the presence of 4-dimethylaminopyridine (DMtVP) ... 

The Corey-Winter reaction provides a useful method for the preparation of olefins that are not accessible by other routes. For instance it may be used for the synthesis of sterically crowded targets, since the initial attack of phosphorus at the sulfur takes place quite distantly from sterically demanding groups that might be present in the substrate molecule. Moreover the required vicinal diols are easily accessible, e.g. by the carbon-carbon bond forming acyloin ester condensation followed by a reductive step. By such a route the twistene 10 has been synthesized ... 

The vicinal diol groups of deoxy sugar phosphates can be cleaved by periodate in the usual conditions without affecting the stability of the phosphate group, so that this reaction can be used for preparative purposes in certain cases. Thus, if 3-deoxy glucose 6-phosphate (23) is... 

In 1970, it was disclosed that it is possible to achieve the conversion of dimethylformamide cyclic acetals, prepared in one step from vicinal diols, into alkenes through thermolysis in the presence of acetic anhydride." In the context of 31, this two-step process performs admirably and furnishes the desired trans alkene 33 in an overall yield of 40 % from 29. In the event, when diol 31 is heated in the presence of V, V-dimethylforrnamide dimethyl acetal, cyclic dimethylformamide acetal 32 forms. When this substance is heated further in the presence of acetic anhydride, an elimination reaction takes place to give trans olefin 33. Although the mechanism for the elimination step was not established, it was demonstrated in the original report that acetic acid, yV, V-dimethylacetamide, and carbon dioxide are produced in addition to the alkene product."... 

Cyanohydrins are starting materials of widespread interest for preparing important compounds such as a-hydroxy acids/esters, a-amino acids, / -amino alcohols, a-hydroxy aldehydes, vicinal diols, and a-hydroxy ketones. Cyanohydrin compounds can be synthesized using various chiral catalysts such as cyclic... 

Unsymmetrical vicinal diols can be prepared from a three-component reaction of aldehydes, CO, and aminotroponiminate-ligated titanium dialkyl complexes. Solutions of Me2TiL,2 (L = N -dimethylaminolroponiminalc) react rapidly with CO at room temperature. Double methyl migration to CO produces an 2-acclonc complex which inserts the aldehyde to afford a titana-dioxolane and releases the unsymmetrical diol upon hydrolysis [65]. 

Replacement of the hydroxamic acid moiety of SAHA by an alternative chelator has been the subject of several studies. Suzuki and Miyata et al. have shown that replacement of the hydroxamic acid of SAHA with a free thiol moiety does not affect the enzymatic HDAC inhibition capability of the compound [57]. Furthermore, replacement of the hydroxamic acid of SAHA by a trifluoromethyl ketone was investigated by Frey et al. (Fig. 8) [58]. The activated ketone is readily hydrated to form the vicinal diol, a structural feature known to bind to zinc-dependent proteases [59]. The in vitro evaluation was done on a partially purified HDAC preparation consisting largely of HDAC 1 and HDAC2 [60], exhibiting an IC50 of 6.7 xM. 

It has been proved that the benzyne intermediate can be easily prepared from o-iodobenzoic acid and potassium peroxydisulfate in sulfuric acid. Water-soluble vicinal diols are converted into their corresponding aldehydes in the presence of Ag(I) catalyst. ... 

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). 

Acetaldehyde has been prepared in part (a). Recalling that vicinal diols are available from the hydroxylation of alkenes, 1,2-ethanediol may be prepared by the sequence... 

The preparation of an aldehyde-SAM was achieved by treating the vicinal diol-SAM with sodium periodate. The preparation of an activated tripodal structure on a hydroxyl terminated SAM has been published by Ichimura and coworkers.64 These authors reported the reaction of SAMs formed by mercapto-alkanols such as 2-mercaptoethanol, 6-mercaptohexanol, and 16-mercaptohexadecanol with SiCl4, with the formation of a tripodal derivative bearing a terminal Si—Cl bond amenable to react with methanol or water. 

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