Cyclic vicinal diols

Cyclic vicinal diols are split to dialdehydes or diketones, depending on the atoms or groups bonded to the carbons carrying the hydroxyls, dx-1,2-Cyclohexanediol and lead tetraacetate yield adipic aldehyde [446, 1155]. 

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... 

Reaction is acid catalyzed Equilibrium constant normally favorable for aide hydes unfavorable for ketones Cyclic acetals from vicinal diols form readily... 

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) ... 

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."... 

The five-membered 1,2-cyclic carbonate was isolated as the only product (regio-selective protection of the vicinal diol system).[255J Analogous formation of a cyclic carbonate containing a secondary hydroxy group is described in reference [256]. 

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... 

Acyloins were converted to mixtures of stereoisomeric vicinal diols by catalytic hydrogenation over copper chromite [972]. More frequently they were reduced to ketones by zinc (yield 77%) [913, 914], by zinc amalgam (yields 50-60%) [975], by tin (yields 86-92%) [173], or by hydriodic acid by refluxing with 47% hydriodic acid in glacial acetic acid (yields 70-90%) [916], or by treatment with red phosphorus and iodine in carbon disulfide at room temperature (yields 80-90%) [917] Procedure 41, p. 215). Since acyloins are readily accessible by reductive condensation of esters (p. 152) the above reductions provide a very good route to ketones and the best route to macro-cyclic ketones [973]. 

The groups of Burczyk, Takeda, and others have made thorough studies of cyclic acetals, such as 1,3-dioxolane (five-membered ring) and 1,3-dioxane (six-membered ring) compounds, illustrated in Fig. 13. They are typically synthesized from a long-chain aldehyde by reaction with a diol or a higher polyol. Reaction with a vicinal diol gives the dioxolane [40-42] and 1,3-diols yield dioxanes [43,44]. 

Synthesis of the cyclic acetal 25 in 63% yield by reaction of the unsaturated bromo-nitrilo sugar 24 (E configuration) with ethylene glycol in the presence of sodium hydroxide has been reported.40 An extension of this work was given for sugars having a vicinal diol... 

First write out the chemical equation for the reaction that takes place. Vicinal diols (1,2-diols) react with aldehydes to give cyclic acetals. 

The Corey-Winter procedure was used to obtain the cyclic thiocarbonate 206 from the corresponding vicinal diol <2000EJ0939>. 

This can be used to create cyclic systems containing ctT-vicinal diol units. 

Osmium tetroxide reacts with double bonds to form cyclic osmate(VI) diesters (10), which can then be hydrolyzed to provide vicinal diols in good yields. > If, however, sodium perio te is also present, the diol is cleaved, as in Scheme 2, and carbonyl compounds are the final products. Periodate serves the additional purpose of regenerating osmium tetroxide, thus permitting the use of this expensive and toxic reagent in minimum amounts. 

The vicinal diol cyclic sulfate from dimethyl tartrate undergoes nucleophilic opening to give substituted malate esters., However, for this application diethyl and diisopropyl L-tartrates give superior yields and selectivities. The asymmetric cyclopropana-tion of the 1 -alkenylboronic ester derived from dimethyl L-tartrate (eq 5) is another example where other tartaric acid derivatives surpass the performance of dimethyl tartrate. ... 

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