Lead tetraacetate oxidations glycol cleavage mechanisms

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. 

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

Oxidative cleavage of 1,2-glycols. Trahanovsky et al.1 have studied the relative rates of oxidative cleavage of 1,2-glycols with CAN and with lead tetraacetate and have concluded that the mechanism in the case of CAN involves formation of a monodentate complex followed by a one-electron cleavage to give an intermediate radical that is oxidized further (scheme I). The cleavage with lead tetraacetate (1, 554-... 

The mechanism of 1,2-cleavage of glycols with sodium bismuthate is generally considered to be similar to that with lead tetraacetate and periodic acid [40CB563], although there is still some controversy [50JCS(C)1907]. A cyclic bismuthate diester is postulated as a plausible intermediate, though the rates of oxidation observed are not so different between cis- and trans-, 2-cyclohexanediols. 

Lead tetraacetate is an alternative to periodate for glycol cleavage. It is particularly useful for glycols that have low solubility in the aqueous media used for periodate reactions. A cyclic mechanism is indicated by the same kind of stereochemistry-reactivity relationships discussed for periodate. Unlike periodate, however, glycols that cannot form cyclic intermediates are eventually oxidized. For... 

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