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TCI Practical Example: Trifluoromethylation Catalyzed by Photoredox Catalyst

We are proud to present the aminotriluoromethylation of alkenes catalyzed by Ru(bpy)₃(PF₆)₂.

Used Chemicals

• 4-Methylstyrene (stabilized with TBC) [M0428]
• Tris(2,2'-bipyridine)ruthenium(II) Bis(hexafluorophosphate) (= Ru(bpy)₃(PF₆)₂) [T3435]
• 5-(Trifluoromethyl)dibenzothiophenium tetrafluoroborate
• Acetonitrile
• Ion-Exchanged Water

Procedure

To a solution of 5-(trifluoromethyl)dibenzothiophenium tetrafluoroborate (0.171 g, 0.50 mmol, 1.0 eq),  Ru(bpy)₃(PF₆)₂ (0.0022 g, 0.0025 mmol, 0.5 mol%) in acetonitrile (10 mL) and ion-exchanged water (1 mL) was added 4-methylstyrene (0.079 mL, 0.60 mmol, 1.2 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 5 hours, water (10 mL) and dichloromethane (15 mL) was added. The reaction mixture was separated. The water phase was extracted with dichloromethane (5 mL, 2 times). The organic phase was corrected, washed with brine (50 mL), dried over sodium sulfate and filtered. The solvent was removed under reduced pressure and the residue was purified by column chromatography on silica gel (hexane:ethyl acetate = 11:1 - 71:29 - 1:4), giving N-(1-(4-methylphenyl)-3,3,3-trifluoropropyl)acetamide as a white solid (80 mg，y. 65%).

Experimenter’s Comments

Acetonitrile was degassed by 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.

Analytical Data

N-(1-(4-Methylphenyl)-3,3,3-trifluoropropyl)acetamide

¹H NMR (400 MHz, CDCl₃); δ 7.20–7.10 (m, 4H), 6.27 (brs, 1H), 5.30 (q, 1H, J = 7.8 Hz), 2.80-2.50 (m, 2 H), 2.34 (s, 3 H), 1.99 (s, 3 H).

¹³C NMR (101 MHz, CDCl₃); δ 169.2, 138.1, 136.8, 129.7, 126.3, 124.1 (q, J = 272 Hz), 48.1, 39.3 (q, J = 27.8 Hz), 23.4, 21.1.

¹⁹F NMR (376.5 MHz, CDCl₃, rt); δ -63.61.

Lead Reference

• Intermolecular Aminotrifluoromethylation of Alkenes by Visible-Light-Driven Photoredox Catalysis
• Y. Yasu, T. Koike, M. Akita, Org. Lett. 2013, 15, 2136.

Other Reference

• Visible Light Photoredox Catalysis with Transition Metal Complexes: Applications in Organic Synthesis
• C. K. Prier, D. A. Rankic, D. W. C. MacMillan, Chem. Rev. 2013, 113, 5322.