Bis(pinacolato)diboron

Used Chemicals

• Tetrakis(triphenylphosphine)platinum(0) [T2485]
• Diphenylacetylene [D0871]
• Bis(pinacolato)diboron [B1964]
• DMF
• Toluene

Procedure

To a degassed solution of diphenylacetylene (100 mg, 0.561 mmol) and bis(pinacolato)diboron (144 mg, 0.567 mmol) in DMF (0.5 mL) and toluene (0.5 mL) was added Pt(PPh₃)₄ (2 mg, 0.25 mol%). The reaction mixture was heated to 80 °C for 24 hours. After this time, the reaction was diluted with toluene (10 mL) and washed with saturated aqueous NH₄Cl (2 x 10 mL). The organic phase was dried over MgSO₄ and concentrated under reduced pressure. Recrystallization from MeOH afforded 1 as a white solid (241 mg, 0.558 mmol, 99%).

Experimenter’s Comments

The reaction mixture was monitored by TLC (CH₂Cl₂:hexane = 2:1, Rf = 0.45).

Analytical Data（Compound 1）

¹H NMR (400 MHz, CDCl₃); δ 7.02-7.09 (m, 6H), 6.94-6.96 (m, 4H), 1.32 (s, 24H).

¹³C NMR (101 MHz, CDCl₃); δ 141.3, 129.3, 127.4, 125.8, 84.1, 24.9.

Lead Reference

• Platinum(0)-catalyzed diboration of alkynes
• T. Ishiyama, N. Matsuda, N. Miyaura, A. Suzuki, J. Am. Chem. Soc. 1993, 115, 11018.

Other References

• Divergent and Stereoselective Synthesis of Tetraarylethylenes from Vinylboronates
• M. Zhang, Y. Yao, P. J. Stang, W. Zhao, Angew. Chem. Int. Ed. 2020, 59, 20090.

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.

References

• T. Niwa, H. Ochiai, Y. Watanabe, T. Hosoya, J. Am. Chem. Soc. 2015, 137, 14313.

References

• Mild iridium-catalyzed borylation of arenes. High turnover numbers, room temperature reactions, and isolation of a potential intermediate
  • T. Ishiyama, J. Takagi, K. Ishida, N. Miyaura, N. R. Anastasi, J. F. Hartwig, J. Am. Chem. Soc. 2002, 124, 390.

References

• Diastereoselective Construction of Functionalized Homoallylic Alcohols by Ni-Catalyzed Diboron-Promoted Coupling of Dienes and Aldehydes
  • H. Y. Cho, J. P. Morken, J. Am. Chem. Soc. 2008, 130, 16140.