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TCI Practical Example: C(sp³)-H Arylation Catalyzed by the Photoredox Catalyst

We are proud to present the C(sp³)-H arylation catalyzed by Ir[(dFppy)₂(bpy)]PF₆.

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 (= THF)
• Dipotassium Hydrogenphosphate (= K₂HPO₄)

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 = 9:1 - 20:3 on silica gel), 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 x 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. Nevertheless, 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 Reference

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