Periodate-Permanganate Cleavage of Olefins

Caution The order of addition must be observed in this procedure or inflammation may occur. 

A 1-liter flask is equipped with a magnetic stirrer, a thermometer immersed in the reaction mixture, and a drying tube. In the flask is placed 100 ml of anhydrous pyridine, and the flask is cooled in an ice-water bath to 15-20° (lower temperatures impede the complex formation). Chromium trioxide (80 g) is added in small portions to the stirred solvent at a rate so as to keep the temperature below 30°. After about one-third of the chromium trioxide has been added, the yellow complex begins to precipitate. At the end of the addition (about 1 hour), a slurry of the yellow complex in pyridine remains. (This form of the complex is apparently a microcrystalline form and is very difficult to handle.) 

The temperature of the stirred solution is readjusted to 15°, and stirring at this temperature is continued until the precipitate reverts to a deep red macrocrystalline form. Petroleum ether (200 ml) is then added to the reaction mixture, the precipitate is allowed to settle, and the solvent mixture is decanted. The residue is washed three times with 200-ml portions of 30-60° petroleum ether, the solvent being removed each time by decantation. The precipitate is collected by suction filtration, dried at room temperature under a vacuum of 10 mm (higher vacuum causes some surface decomposition), and stored in a desiccator. (The complex readily forms a hydrate, which is not soluble in organic solvents. Consequently, protection from moisture is necessary.) 

Oxidation with Chromium Trioxide-Pyridine Complex General Procedure 

A 5% solution of chromium trioxide-pyridine complex in dry methylene chloride is prepared. The alcohol (0.01 mole) is dissolved in dry methylene chloride and is added in one portion to the magnetically stirred oxidizing solution (310 ml, a 6 1 mole ratio) at room temperature. The oxidation is complete in 5-15 minutes as indicated by the precipitation of the brownish black chromium reduction products. The mixture is filtered and the solvent is removed (rotary evaporator) leaving the crude product, which may be purified by distillation or recrystallization. Examples are given in Table 1.1. 

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