(2,2'-Bipyridine)bis[2-(2,4-difluorophenyl)pyridine]iridium(III) Hexafluorophosphate

Used Chemicals

• Methyl Pentafluorobenzoate [P1418]
• (2,2'-Bipyridine)bis[2-(2,4-difluorophenyl)pyridine]iridium(III) Hexafluorophosphate (= Ir[(dFppy)₂(bpy)]PF₆) [B4944]
• Quinuclidine [Q0062]
• Tetrahydrofuran
• Dipotassium Hydrogenphosphate

Procedure

To a solution of quinuclidine (22.4 mg, 0.201 mmol, 0.20 eq), Ir[(dFppy)₂(bpy)]PF₆ (18.0 mg, 0.0165 mmol, 1.7 mol%), K₂HPO₄ (0.358 g, 2.07 mmol, 2.1 eq) in THF (10 mL) was added methyl pentafluorobenzoate (0.146 mL, 1.00 mmol, 1.0 eq) at rt under N₂. The mixture was placed at a distance of 2-3 cm from Blue LED lamp. The orange solution was stirred at rt under visible light irradiation. After 4.5 hours of irradiation, the solvent was removed in vacuo. The residue was diluted with dichloromethane and filtered through a silica gel pad. The filtrate was concentrated and purified by column chromatography (hexane : ethyl acetate on silica gel, hexane : ethyl acetate = 9 : 1 → 20 : 3), giving compound 1 as a colorless oil (125 mg, y. 45%).

Experimenter’s Comments

Tetrahydrofuran was degassed with nitrogen for 1 hour before use.
Irradiation of visible light was performed with Kessil A160WE Tuna Blue 40W×2.
The reaction mixture was monitored by ¹H NMR, TLC (hexane : ethyl acetate = 10 : 1, Rf = 0.26).
The reaction was performed at rt, however the internal temperature rose up to 40 ˚C due to the insufficient cooling. Neverthelss, the reaction proceeded without any problems.

Analytical Data（Compound 1）

¹H NMR (400 MHz, CDCl₃); δ 5.27 (t, J = 7.8 Hz, 1H), 4.09 (q, J = 7.3 Hz, 1H), 3.97 (s, 3H), 3.99−3.90 (m, 1H), 2.40−2.31 (m, 1H), 2.24−2.15 (m, 1H), 2.11-2.06 (m, 2H).

¹³C NMR (101 MHz, CDCl₃); δ 160.2, 145.8, 143.4, 124.8, 104.5, 71.7, 69.4, 53.3, 32.4, 27.0.

¹⁹F NMR (376.5 MHz, CDCl₃); δ −140.34 (d, J = 23 Hz, 2F), −142.95 (d, J = 23 Hz, 2F).

Lead Reference

• Direct C-H Multifluoroarylation of Ethers through Hydrogen Atom Transfer Using Photoredox Catalysis
• J. Wang, B. Huang, Y. Gao, C. Yang, W. Xia, J. Org. Chem. 2019, 84, 6895.

Other References

• A Retrosynthetic Approach for Photocatalysis
• D. Petzold, M. Giedyk, A. Chatterjee, B. König, Eur. J. Org. Chem. 2019, 10, 1193.