Chromic acid resin supports

A compound prepared and first described as nicotinium dichromate (NDC) by Palomo et al.,379 was later shown by X-ray-crystal analysis380 to be a betainic mixed anhydride of nicotinic and chromic acid (NACAA). Because of its unique structure, it deserves a close scrutiny of its oxidative properties.381 Replacement of the chloride anion in the quaternary ammonium resin, Dowex 1-X8, for the dichromate anion, leads to a polymer supported dichromate, which is able to make selective benzylic oxidations.382 Finally, poly[vinyl(pyridinium dichromate)] (PVPDC), a polymeric analogue of PDC, must be mentioned whose use in the oxidation of alcohols allows for a very easy work-up.383... 

Chromic acid also becomes a selective oxidant for the preparation of aldehydes and ketones when it is supported on an anion exchange resin (Amberlyst A-26 Table 16). The reaction appears to be general and highly tolerant of a wide range of solvents, unlike many resin-based oxidations where the availability of the oxidant is critically dependent upon the nature of the solvent. 

Cainelli, G., Cardillo, G., Orena, M., Sandri, S. Polymer supported reagents. Chromic acid on anion exchange resins. A simple and practical oxidation of alcohols to aldehydes and ketones. J. Am. Chem. Soc. 1976, 98, 6737-6738. 

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