Reduction of a nitrile with DIBAH; Aldehydes
Submitted Oct 21, 2010, published Oct 21, 2010
Alpha-bromo-p-tolunitrile (Acros Organics)
DIBAH 1M (Aldrich)
Toluene (distilled over NaH)
All glassware was stored at 110°C or at least 10 hours prior to the reaction. Alpha-bromo-p-tolunitrile (2.99g 1.53x10-2mol) was added to a 250mL 3 necked round bottom flask fixed with a 25mL dropping funnel. The assembled reactor was sealed with rubber septa, purged with Nitrogen (UHP) for 10 min, then dried with a heat-gun under vacuum. Anhydrous toluene (~100mL) was added to the reactor via a solvent bridge. The solution was then stirred and cooled in an ice bath. After 30 minutes at 0°C, 1M DIBAH (17.6mL 1.76x10-2mol) was added to the dropping funnel. The DIBAH was added dropwise from the dropping funnel into the nitrile solution. Once all of the DIBAH was added to the flask, the contents were allowed to react with stirring at 0°C over the course of which the solution turned from colorless to light yellow. After 3 hours, the solution was checked by TLC (80% dichloromethane 20% hexanes) spotted against the starting material and revealed that no nitrile remained.
Cold 1M aqueous HCL(~100mL) was added to the solution and allowed to stir at room temperature for 30 minutes over the course of which the solution turned colorless and white emulsion formed. The entire content of the flask was filtered through Celite. The two phases were then separated. The organic phase was washed 3x50mL with 1M aqueous HCl. Then all of the aqueous phase was washed 3x50mL with dichloromethane. All of the organic solution was collected and dried over sodium sulfate. The dried organic solution was concentrated then analyzed by HNMR in CDCl~3~ to be 98% p-bromomethyl benzaldehyde with a total mass of 2.74g (88% yield).
HNMR in CDCl~3~: 2H singlet 4.44ppm, 2H doublet 7.48ppm, 2H doublet 7.79ppm, 1H singlet 9.94ppm
Changtong, C.; Shuster, C.; Lombardi, J. L.; Connors, R. E. Composite Molecules that Generate, Store, and Release Singlet Oxygen. 34th Northeast Meeting of the American Chemical Society, Binghampton, N.Y., Oct. 2006.
Keywords: aldehydes, DIBAH, DIBAL, DIBALH, diisobutylaluminum, hydride, nitrile, reduction