Cleavage of ketals

Johnstone C, Kerr W J, Scott J S (1996) Selective cleavage of ketals and acetals under neutral, anhydrous conditions using triphenylphosphine and carbon tetrabromide. Chem Commun 1996 341-342... 

Fig (19) Octalin ketal (163) is converted to kete dithioacetal (164) by the cleavage of ketal function and condensation with carbon disulfide and methyl iodide. Subjection of (164) to the action of dimethylsulfonium niethylide and acid hydrolysis leads to the formation of unsaturated lactone (165).lts furan silyl ether derivative is caused to undergo Diets-Atder reaction with methyl acrylate to obtain salicyctic ester (166) which is converted by standard organic reactions toabietane ether (167). It is converted to aiiylic alcohol (168) by epoxidation and elimination. Alcohol (169) obtained from (168) yields orthoamide which undergoes transformation to amide (170). Its conversion to the previously reported intermediate has been achieved by epoxidation, elimination and hydrolysis. 

Cleavage of ketals (12, 347-348). Certain chiral cyclic ketals are cleaved by R2CuLi/BF30(C2H5)2 diastereoselectively to chiral secondary alcohols.4... 

The combined reagent system 2,2 -bipyridinium chlorochromate / MCPBA cleaves 2-phenyl-l,3-dioxolanes to give the 2-hydroxyalkyl benzoates <97TL1733> and the role of single electron transfer in the photosensitised cleavage of ketals has been the subject of a detailed mechanistic study <97T2219>. 

Cleavage of ketals. Dimethyl and diethyl ketals are converted into ketones in 85-95% yield by treatment with iodotrimethylsilane in chloroform saturated with propene, added to eliminate traces of HI in the reagent. Ethylene ketals also react, but give a complex mixture of products. Thioketals are completely stable. The probable mechanism is shown in equation (I). 

Sulfuric acid Dehydration of alcohols with cleavage of ketals... 

Ketones from y -ketocarboxylic acid esters with protection of the keto group as cyclic ketal Decarboxylation with cleavage of ketals... 

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