Diisobutylaluminum Hydride (19% in Hexane, ca. 1.0mol/L)

• Diisobutylaluminum Hydride (19% in Hexane, ca. 1.0mol/L) (= DIBAL) [D2971]
• Sodium tert-Butoxide (= NaOtBu) [S0450]
• Ethyl 2-Bromobenzoate [B1514]
• THF

To a solution of NaOtBu (460 mg, 4.8 mmol) in THF (2.4 mL) was added dropwise DIBAL (4.8 mL, 4.8 mmol) at 0 °C and the mixture was stirred at rt for 2 hours to prepare SDBBA solution as a colorless liquid.
Ethyl 2-bromobenzoate (230 mg, 1.0 mmol) in THF (2 mL) was added SDBBA (2.4 mL, 1.6 mmol, ca. 0.67 mol/L in THF/hexane) at 0 °C and the mixture was stirred at same tempferature for 1 hour. After that quenched by 2 mol/L HCl aq. (5 mL) and the residue was diluted with dichloromethane (20 mL x 2) and dried over sodium sulfate and filtered. The solvent was removed under reduced pressure and the residue was purified by column chromatography (on silica gel, dichloromethane:hexane = 1:4), giving 2-bromobenzaldehyde as a colorless liquid (109 mg, 59% yield).

The reaction mixture was monitored by UPLC.
Hydrogen gas was produced during the preparation of SDBBA solution.
SDBBA can reduce esters to aldehydes under the mild conditions compared to other reducing agents.

2-bromobenzaldehyde

¹H NMR (400 MHz, CDCl₃); δ 10.4 (s, 1H), 7.92 (m, 1H), 7.66 (m, 1H), 7.45 (m, 2H).

• New Method for Synthesis of Aldehydes from Esters by Sodium Diisobutyl-t-butoxyaluminum Hydride
• S. J. In, A. D. Keun, Chem. Lett. 2007, 36, 886.