Chromium! VI oxide-3,5-dimethylpyrazole

Although chromium(VI) oxide-(3,5-dimethylpyrazole) is also a good oxidant for allylic C—bonds, it is surprising that this reagent has not been more widely adopted. 

Allylic oxidations may also be carried out with the related Chromium(VI) Oxide-3,5-Dimethylpyrazole (DMP) complex. ... 

In contrast to the Collins reagoit, the complex formed by 3,5-dimethylpyrazole with chiomium(VI) oxide (2) is very soluble in dichloromethane. Hence, reactions (up to 0.1 mol scale) can be carried out in the minimum amount of solvent. Generally, 2.5 equiv. of complex, generated in situ, gives good yields of aldehydes and ketones. In addition, upon woric-up most of the chromium salts may be precipitated by dilution with diethyl ether. 

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