Glycols oxidation with lead tetraacetate

Oxidation with lead tetraacetate is also useful for dii osii the 1,2-glycol group in nonreducing sugars and derivatives (52). Here the chromatogram is wetted with a spray of xylene, and then a 1% solution of lead tetraacetate in benzene is applied. On evaporation of the benzene the glycols are indicated by white zones on a brown background. 

A few rate coefficients for oxidation by lead tetraacetate have been reported. These, together with those for some carbohydrates, are referred to in the section on glycols (p. 349). 

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... 

By-products of the above reactions are 1,2,6-tribenzoyl-D-mannitol and 1,2,6-tribenzoylsorbitol. The structure of the first was shown in two ways. Brigl and Griiner converted it to the known 1,2,5,6-tetra-benzoyl-3,4-isopropylidene-D-mannitol. Hockett and Fletcher oxidized it to dibenzoyl-D-glyceraldehyde with lead tetraacetate. This, and the fact that the rate of oxidation was like that of glycerol, not of ethylene glycol, established the structure. 1,2,6-Tribenzoylsorbitol consumed... 

The di-(cyclohexylidene)-D-mannitol contained a terminal a-glycol group because (a) oxidative scission with lead tetraacetate consumed one mole of the oxidant and gave one mole of formaldehyde, together with an acid-labile derivative of D-arabinose, and (b) its dimethyl ether yielded the known crystalline 5,6-dimethyl-D-mannitol (1,2- is identical) when heated with aqueous acid.1 0 Since graded acidic hydrolysis of the diketal furnished 3,4-cyclohexylidene-D-mannitol,3 it must have possessed the 1,2 3,4-structure and the parent triketal must have been 1,2 3,4 5,6-tri-(cyclohexylidene)-D-mannitol. 

Methylenecyclobutane has been converted to cyclobutanone by oxidation to the corresponding glycol with performic acid and subsequent cleavage of the glycol with lead tetraacetate (75% over-all). ... 

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. 

The tetrahydrochromane (2) is oxidized by /M-chloroperbenzoic acid to 6-ketonon-anolide (5) under carefully controlled conditions (2.8 equiv. of peracid, methylene chloride, room temperature). The reaction is postulated to involve the hydroxy peracid (4) as an intermediate which undergoes fragmentation. Use of perphthalic acid gives the glycol (3). which on cleavage with lead tetraacetate gives (5). 

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