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 Simple way for Oxidation of Organoboranes: (+)-Isopinocampheol
  • Simple way for Oxidation of Organoboranes: (+)-Isopinocampheol
  • (+)-Isopinocampheol (CAS no.: ), which is also known as (+)-3-Pinanol, could be produced as the following synthetic routes.



    A. (+)-. A dry, 250-mL, three-necked, round-bottomed flask, equipped for magnetic stirring, and with a nitrogen inlet vented through a mercury bubbler, a rubber septum, and a thermometer, is flushed with nitrogen and charged with 13.75 g (0.101 mol) of (-)-α-pinene and 25 mL of tetrahydrofuran). The mixture is cooled to 0°C in an ice-water bath, magnetic stirring is initiated, and 58.0 mL (0.055 mol) of 0.95 M borane-tetrahydrofuran solution is added via syringe at a rate such that the temperature of the reaction mixture remains below 5°C. After the addition is complete, the cooling bath is removed. The reaction mixture is allowed to warm to room temperature and stir for 2 hr to ensure complete reaction.

    B. (+)-Isopinocampheol. To the stirred solution of (+)-diisopinocampheylborane in tetrahydrofuran, prepared above, 50 mL of distilled water is slowly added dropwise via syringe [CAUTION!] followed by the slow addition of 16.41 g (0.107 mol) of solid sodium perborate tetrahydrate through an appropriate addition funnel at a rate such that the temperature of the reaction mixture does not exceed 35°C. Stirring is continued at room temperature (22°C) for 2 hr to ensure completion of the oxidation reaction. The contents of the flask are then poured into 70 mL of ice-cold water in a separatory funnel. After thorough mixing, the organic layer is removed and the aqueous layer is extracted twice with 25 mL of ether. The combined ether extracts are washed twice with 20-mL portions of water and then with 50 mL of saturated aqueous sodium chloride solution. The ether layer is dried over anhydrous magnesium sulfate, filtered, and concentrated on a rotary evaporator. The crude product is purified by short-path vacuum distillation to give 14.1–14.3 g (91–92%) of isopinocampheol, bp 68°C (0.7 mm), as white needles (mp 53–55°C) that crystallize in the receiving flask. Recrystallization from pentane gives pure isopinocampheol as needles, mp 54–55°C (uncorrec.), [α]D25 34.4° (benzene, c10) indicating 96.4% enantiomeric purity based on the highest reported literature value of 35.7°.


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