Vicinal diols cyclic acetals from

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

This reaction looks much like the formation of a cyclic acetal from a 1,2-diol and a ketone. The intermediate breaks down to form the two carbonyl compoimds. As you can see from the mechanism (Fig. 16.74), only vicinal diols can imdeigo this cleavage reaction. 

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 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]. 

The vicinal diol 216, prepared in 10 steps from quinic acid, was elaborated into V-alkylated 2-epi-valienamines 217 in variable (16-98%) yield by reaction with Viehe s salt followed by Pd(0)-catalysed coupling with a range of primary e.g. R = H = Et, Bu, Hept, Oct, cyclohexyl, Bn) and secondary amines e.g. R = R = Bu, cyclohexyl, Pr). Carbocyclic influenza neuraminidase inhibitors 219 (n = 3-8) with a cyclic amine side-chain have also been prepared via Pd(0)-catalysed coupling of acetate 218 with the corresponding cyclic amines. The use of pentafunctional quinic acid as a polyoxygenated scaffold for combinatorial synthesis has also been described. ... 

Cyclic benzylldene acetals derived from ois-related vicinal diols on pyranosyl rings, on irradiation in the presence of N-bromosuccinimide and water, react to give the corresponding axially oriented monobenzoate, illustrated in Scheme 2. 

Synthesis of Monosaccharide Derivatives.—New approaches to the synthesis of glycosides, including the alkoxylation of N-furanosyl-lactams, the reaction of l-0-acetyl-2,3,5-tri-0-benzoyl-P-D-ribofuranose with cyclic amide acetals derived from vicinal diols (see Vol. 10, p. 16), the Lewis acid-catalysed alcoholysis of sugars with an activated anomeric centre (see Vol. 10, p. 11), and the glycosidation of glycopyranosyl halides catalysed by silver trifluoromethanesulphonate (triflate), have been reviewed. A general review of carbonyl compounds has also dealt with some aspects of glycoside synthesis. 

In addition to the approach outlined in Scheme 4, several other approaches to the synthesis of glycofuranosides have been reported during the past year. Hanessian and Banoub have used cyclic amide acetals derived from vicinal diols as the source of the aglycone in condensations with l-0-acetyl-2,3,5-tri-0-benzoyl-jS-D-ribofuranose in the presence of stannic chloride (Scheme 5). Disaccharide derivatives are obtained when the cyclic amide acetal is derived from carbohydrate vicinal diols (Scheme 6), and selective methanolysis of the formate ester exposed an hydroxy-group that can be subjected to further manipulation or glycosylation. 2,3,5-Tri-0-benzoyl-a)8-L-arabinofuranosyl bromide or chloride has been condensed with 4-nitrophenyl 2,3-di-O-acetyl-a-L-arabinofuranoside to yield, after deacylation, 4-nitrophenyl 5-O-a-L-arabinofuranosyl-a-L-arabino-furanoside, with jS-peltatin A [isolated from podophyllin Podophyllum peltatum)] in glycosidation of the phenolic 8-OH group in an attempt to reduce... 

The presence of neighboring pairs of hydroxy groups in the sugars allows for the formation of cyclic ether derivatives. For example, it is possible to synthesize five- or six-membered cyclic sugar acetals from the vicinal (and also from some jS-diol) units by treating them with carbonyl compounds (Section 17-8). 

Cyclic Acetal Formation from Vicinal Diols... 

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