Cyclic acyloxonium ions

Paulsen, H., Cyclic Acyloxonium Ions in Carbohydrate Chemistry, 26, 127-195... 

Paulsen, H, Cyclic acyloxonium ions in carbohydrate chemistry, Adv. Carbohydr. Chem. Biochem.,... 

There are several ways to prepare cyclic acyloxonium ions. We will only discuss the reaction of antimony pentachloiide with vicinal diacetates and vicinal chloro- or bromo-acetates because this technique has allowed a most interesting reaction in carbohydrate chemistry (reaction 7.9). The acyloxonium cation can react in two ways the so-called kinetic reaction takes place at the most charged site as, for example with H2O and OH, to give the unstable orthoester 7.20 which opens to the cis-hydroxyl ester 7.21. The so-called thermodynamic reaction, with acetate in an acidic medium, choride, and bromide leads to the formation of the trans product 7.22 (X = AcO, Cl, Br). 

Paulsen, H., Cyclic Acyloxonium Ions in Carbohydrate Chemistry, 26,127-195 Paulsen, H., and TODT, K., Cyclic Monosaccharides Having Nitrogen or Sulfur in the Ring, 23, 115-232 Paulsen, H. See also, Heyns, K. 

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