Bis(pinacolato)diboron

Details:

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Used Chemicals

• 3-Iodobenzalehyde [I0611]
• Bis(pinacolato)diborane [B1964]
• Palladium(II) Acetate (Purified) [P2161]
• Potassium Acetate [P2786]
• DMF

Procedure

To the solution of 3-iodobenzalehyde (1.16 g, 5.00 mmol) in dry DMF (15.0 mL) were added potassium acetate (981 mg, 10.0 mmol), palladium(II) acetate (112 mg, 0.500 mmol, 10 mol%) and bis(pinacolato)diborane (1.27 g, 5.00 mmol). The reaction mixture was stirred at 80 ºC for 7 h. The reaction mixture was cooled to room temperature and quenched with H₂O (15 mL) and saturated NH₄Cl aq. (10 mL), then the mixture was extracted twice with hexane : EtOAc = 4 : 1. The combined organic layer was washed with H₂O (50 mL) and brine (50 mL), dried over Na₂SO₄, and concentrated under reduced pressure to afford the crude product as a yellow oil. The crude product was purified by column chromatography on silica-gel (hexane → hexane : EtOAc = 1:1) to afford 3-formylphenylboronic acid pinacol ester as a yellow oil (500 mg, 2.15 mmol, 43%).

Experimenter's Comments

(1) DMF was dried over molecular sieves.

(2) Completion of the reaction was confirmed by TLC (hexane : EtOAc = 1 : 1, Rf = 0.30) and GC.

Analytical Data（3-Formylphenylboronic Acid Pinacol Ester）

¹H NMR (400 MHz, CDCl₃); δ 10.1 (s, 1H), 8.30 (s, 1H), 8.06 (d, J = 4.0 Hz, 1H), 7.99 (ddd, J = 1.6, 1.8, 7.8 Hz, 1H), 7.53 (t, J = 8.0 Hz, 1H), 1.37 (s, 12H).

Lead Reference

• The bulky side chain of antillatoxin is important for potent toxicity: rational design of photoresponsive cytotoxins based on SAR studies
  • K. Okura, S. Matsuoka, M. Inoue, Chem. Commun. 2013, 49, 8024.