Hydroxyketone cleavage periodic acid

Periodic acid is a selective reagent for the cleavage of 1,2-dioIs and related substances, such as l-amino-2-hydroxy compounds, 1,2-diketones and a-hydroxyketones. With periodic acid, corticosteroid compounds (where R= H, OH), can be transformed into 17(Lcarboxylic acids and formaldehyde. 

The aldol addition of Figure 13.47 can also be carried out in such a fashion that the crude silyl ether-containing aldol adducts are treated directly with periodic acid without prior aqueous workup. In that case, the silyl ether and oc-hydroxyketone cleavages both occur in one operation. 

Oxidative cleavage of the 1,2-dihydroxy- and a-hydroxyketone moieties to carbonyl and carboxylic acid groups, respectively, was accomplished with lead tetracetate and periodic acid (Scheme 74) <1997JOC7430, 2005AGE6187>. 

Periodic acid also cleaves carbon-carbon bonds of a-hydroxyketones and a-hydroxyaldehydes by a similar mechanism. Following are abbreviated structural formulas for these functional groups and the products of their oxidative cleavage by periodic acid. As a way to help you understand how each set of products is formed, each carbonyl in a starting material is shown as a hydrated intermediate that is then oxidized. In this way, each oxidation can be viewed as being analogous to the oxidation of a glycol. 

Notable were highly enantioselective additions of N-phosphonyl imines with dialkyl zinc or hydroxyketones and a one-pot reaction of alkynylzirconocenes with alkynyl phosphazenes and zinc carbenoids to give single isomer cyclopropylphosphonamides. The importance of enantioselective and dynamic kinetic asymmetric transformations is illustrated in many publications. Other interesting reports cover the use of phosphoramidates for the synthesis of allylic amines as well as the first example of C-P cleavage of a-aminophosphono acids using periodate. 

Schmid and co-workers (124) have described a new degradation of (-)-kopsine (325) to (-)-aspidofractinine (326). Sodium periodate cleavage of the hydroxyketone under acidic conditions gave a keto acid which was esterified. Oxidation with chromium trioxide in pyridine at room temperature for 48 hr then gave the 5,6-dehydro compound 327. Hydrolysis of 327 under acidic conditions gave the unstable enamine 328... 

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