2,3-Dichloro-5,6-dicyano-1,4-benzoquinone

Used Chemicals

• DDQ [D1070]
• Trifluoromethanesulfonic Acid (= TfOH) [T0751]
• 9,10-diphenylanthracene [D1689]
• Dichloromethane

Procedure

To a solution of 9,10-diphenylanthracene (200 mg, 0.61 mmol) and DDQ (412 mg, 1.8 mmol, 3.0 equiv) in dichloromethane (19 mL) was added TfOH (1 mL) at 0 °C and the mixture was stirred for 1 hour. The reaction mixture was quenched with sat. NaHCO₃ aq. (20 mL), filtered through celite pad and the insoluble was washed with dichloromethane (100 mL). The organic layer was washed with sat. NaHCO₃ aq. and dried over Na₂SO₄.The solvent was removed under reduced pressure and the residue was purified by column chromatography (hexane:dichloromethane = 0:1 - 1:3 on silica gel) to give rubicene (131 mg, 67%) as a red solid.

実施者コメント

The reaction mixture was monitored by TLC (hexane:dichloromethane = 3:2, R_f = 0.37).
The color of reaction mixtures changed like below;
Before adding TfOH: yellow
After adding TfOH: blue
After quenching with sat. NaHCO₃ aq.: red.

Analytical Data（Rubicene）

¹H NMR (400 MHz, CDCl₃); δ 8.62 (d, J = 8.6 Hz, 2H), 8.34 (d, J = 7.6 Hz, 2H), 8.04 (d, J = 6.8 Hz, 2H), 7.98 (d, J = 7.0 Hz, 2H), 7.79 (dd, J = 8.6, 6.6 Hz, 2H), 7.45 (td, J = 7.6, 0.8 Hz, 2H), 7.39 (td, J = 7.6, 0.8 Hz, 2H).

Lead Reference

• Facile Synthesis of Rubicenes by Scholl Reaction
• M. Kawamura, E. Tsurumaki, S. Toyota, Synthesis 2018, 50, 134.

References

• Protection for the Hydroxyl Group, Including 1,2- and 1,3-Diols
  • P. G. M. Wuts, in Greene’s Protective Groups in Organic Synthesis, 5th ed., ed. by P. G. M. Wuts, John Wiley & Sons, Inc., Hoboken, New Jersey, 2014, Chap. 2, 17.