Chromates, reactions Chromic anhydride

Reaction of chromic anhydride (CrOg) with t-butanol yields t-butyl hydrogen chromate, a powerful oxidant suitable for allylic oxidation of electron-deficient alkenes. Oxidations using t-BuOCr03H in CCI4 are highly exothermic and should be performed with caution. 

When potassium chromate is treated with concentrated sulphuric acid, the chromic acid, which would be formed by double decomposition, becomes dehydrated by the concentrated sulphuric acid and chromic anhydride is produced. A similar reaction takes place when potassium dichromate is treated with concentrated sulphuric acid. 

Oxidation. Reaction of chromic anhydride with HMDO in halogenated solvents leads to dissolution of the solid with formation of bis(trimethylsilyl)chromate (eq 14). 

OL-Iodo ketones, a-lodo ketones are usually prepared by reaction of enol acetates with NIS. A new method involves reaction of an alkene with silver chromate and iodine in the presence of pyridine. The actual reagent is presumably a mixed anhydride of hypoiodous acid and chromic acid. Dichloromethane is the most useful solvent. ... 

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