Selective oxidation of 1,2-diols

See also page 1234, Section 18 for some other selective oxidations of diols. 

In 1976, Ueno and Okawara highlighted the fact that no oxidation of primary saturated alcohols to aldehydes via tin alkoxides had been reported in the literature and published a procedure for the selective oxidation of secondary alcohols.25 Interestingly, rather than performing the oxidation on pre-formed tin alkoxides, these researchers subjected a mixture of the diol and (Bu3Sn)20 in CH2C12 to the action of Br2. Regardless of the fact that no complete formation of tin alkoxides is secured and no HBr quencher is added, this method may provide useful yields of hydroxyketones during the selective oxidation of diols.26... 

Subsequent researchers introduced substantial improvements on the Ueno and Okawara s protocol of selective oxidations via tin alkoxides and broadened considerably the scope of its application.223 24b,c Thus, it was established that good yields in the selective oxidation of diols—and even triols and tetrols can be achieved in two steps i) pre-formation of a tin alkoxide, by reaction with either (Bu3Sn)20 or Bu2SnO with elimination of water by molecular sieves or azeotropic distillation of water ii) treatment of the tin alkoxide with Br2 or NBS in the presence of a HBr quencher. 

M. Fetizon, M. Golfier, and J. M. Louis, Highly selective oxidations of diols by silver carbonate, Chem. Commun., (1969) 1102 A new synthesis of lactones application to ( )-mevalonolactone, ibid., (1969) 1118-1119. 

Reagent mixtures which utilize a catalytic metal complex, usually with a cooxidant (analogous to the Pt/02 reagent) for the selective oxidation of diols to lactones have been studied recently, with some interesting results. 

The selective oxidation of diols in which one or both hydroxy groups are allylic has been reported on a number of occasions. Reagents which have proved use for this include silver carbonate on Celite, barium manganate/ and manganese dioxide, as illustrated in equations (29)-(31). 

This IncermediaCe can also be implicated in an earlier reagent described by Crosby et al for the selective oxidation of diols (38). Treatment of polymer-bound thloanlsole with chlorine affords the dlchlorlde which can selectively carry out the oxidation by a similar intermediate (Equation 10). 

Likewise, the total synthesis of the antifungal agent GM222712 was accomplished by a selective oxidation of diol 838 to hemiacetal 839 (Scheme 3.332) [1137]. 

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