Hydroxy- or a-Alkoxy-substituted

Stannylene derivatives of carbohydrates are converted by brominolysis into a-ketols [equation (30)], °° and a-alkoxy-, a-aryloxy-, and a-benzyloxy-alde-hydes are obtained in good yield from the osmium tetraoxide oxidation of the olefinic bond of allyl ethers.  

Tamura, T. Kawasaki, N. Gohda, and Y. Kita, Tetrahedron Lett., 1979, 1129. 

Electrolysis of a,a -dibromo-ketones in acetic acid gives reasonable yields of a-acetoxy-ketones the ratio of secondary to tertiary products can be controlled by the choice of conditions [equation (32)].  

Sonoda, Y. Seki, and K. Kawamoto, Angew. Chem. Int. Ed. Engl., 1979,18, 393. 

The anion of a-trimethylsilyloxybenzylphosphonate reacts with acid chlorides or anhydrides to give good yields of mixtures of a-ketols in which the benzylic alcohol predominates [equation (33)].  

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Treatment of a-hydroxy- or a-alkoxy-substituted hexahydro-oxazolo[3,4-r ]pyridin-3-ones with an acid allows for the generation of bicyclic iV-acyliminium ions which can then smoothly react with nucleophiles, usually with high diastereoselectivities (Scheme S3) <2001EJ01267, 1998SL206>. 

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