Lead tetraacetate, glycol cleavage

Lead tetraacetate and periodic acid complement one another in their applicability as reagents for glycol cleavage. The water sensitive lead tetraacetate is used in organic solvents, while periodic acid can be used for cleavage of water-soluble diols in aqueous medium. 

Lead tetraacetate is an important reagent for glycol cleavage, which has the stoichiometry... 

Cyelobutanone has been prepared by (1) reaction of diazomethane with ketene,4 (2) treatment of methylenecyclobutane with performic acid, followed by cleavage of the resulting glycol with lead tetraacetate,s (3) ozonolysis of methylenecyclobutane, (4) epoxidation of methylene-cyclopropane followed by acid-catalyzed ring expansion,7 and (5) oxidative cleavage of cyclobutane trimethylene thioketal, which in turn is prepared from 2-(co-chloropropyl)-l,3-dithiane.8... 

Another is the oxidation of a secondary alcohol to a ketone (9-3), where A and B are alkyl or aryl groups and Z is also CrOjH. In the lead tetraacetate oxidation of glycols (9-7) the mechanism also follows this pattern, but the positive leaving group is carbon instead of hydrogen. It should be noted that the cleavage shown is an example of an E2 elimination. 

GRUNDMANN ALDEHYDE SYNTHESIS. Transformation of an acid into an aldehyde of the same chain length by conversion of the acid chloride via the diazo ketone to the acetoxy ketone, reduction with aluminum isopropoxide and hydrolysis to the glycol, and cleavage with lead tetraacetate. 

Review.1 The reactions of C6H5I(OAc)2 are mainly oxidations in which iodine(III) is reduced to iodine(I) and closely resemble those of lead tetraacetate, such as cleavage of glycols. For this reaction, phenyliodine(III) bis(trifluoroacetate) is the preferred reagent (6, 301). 

II. Mechanism of Glycol-cleavage Oxidation by Lead Tetraacetate. 11... 

Although carbinols were found not to be oxidized by lead tetraacetate in acetic acid, they were attacked in less polar solvents, and glycol-cleavage was also more rapid in these solvents23 for example, the rate of oxidation of trans-l, 2-cyclohexanediol in tetrachloroethane was 5,000 times that in acetic acid. The kinetics was no longer true second-order in the media of low polarity, but approached this state as the concentration of acetic acid... 

This lack of an entirely consistent pattern has not prevented the successful application of glycol-cleavage by lead tetraacetate to a wide variety of structural problems. In relating oxidation data to structure, it has been necessary only to recognize that a single approach to a chemical problem is never fully adequate and that other lines of evidence must be sought. 

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