Poly -chromium trioxide

Again, as with pyridopyrimidines, the main reaction is oxidation of di- or poly-hydro derivatives to fully aromatic structures, often merely by air or oxygen. In some cases the reagent of choice is mercury(II) oxide, whilst other reagents used include sulfur, bromine, chloranil, chromium trioxide-acetic acid, hydrogen peroxide, and potassium ferricyanide, which also caused oxidative removal of a benzyl group in the transformation (306) (307)... 

Small quantities can be distilled at about 75°C/1.3 mbar, but larger amounts are liable to explode violently owing to local overheating [1], An attempt to prepare an analogous poly(dimethylsilyl) chromate by heating a polydimethylsiloxane with chromium trioxide at 140°C exploded violently after 20min at this temperature [2], See related alkylsilanes, metal oxides... 

I. Hoffman, B. Lindberg, and S. Svensson, Determination of the anomeric configuration of sugar residues in acetylated oligo- and poly-saccharides by oxidation with chromium trioxide in acetic acid, Acta Chem. Scand., 26 (1972) 661-666. 

Poly(vinylpyridinium) chlorochromate (PVPCC) is obtained as a liright-orange solid by adding chromium trioxide and concentrated hydrochloric acid to an aqueous suspension of cross-linked poly(vinylpyridine) (PVP) resin (50-100 mesh). Oxidations of primary and secondary alcohols to carbonyl compounds are carried out on heating with a slight excess of the resin at 75-80 °C. The reaction is best carried out in cyclohexane [612]. 

Because the reagent is slightly acidic, it cannot be used to oxidize acid-sensitive compounds [605. For easier isolation of the products, the complex may be formed in the presence of alumina. After the reagent is stirred with the alcohol at room temperature for 2 h, the aldehyde is isolated by filtration and evaporation of the filtrate [604. Another solid-support oxidant of pyridinium chlorochromate is prepared by treatment of cross-linked poly(vinylpyridine) with chromium trioxide and hydrochloric acid (equation 212) [612]. 

---