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TCI Practical Example: Oxidation of a Hydroxy Group Using TPAP

We are proud to present the oxidation of trans-2-phenyl-1-cyclohexanol using TPAP as an oxidation catalyst. TPAP can oxidize hydroxy groups in a catalytic amount in the presence of a reoxidant. Additionally, work-up and removal of TPAP can be done easily.

Used Chemicals

• trans-2-Phenyl-1-cyclohexanol [P1174]
• Tetrapropylammonium Perruthenate (= TPAP) [T1559]
• 4-Methylmorpholine N-Oxide (= NMO) [M2192]
• Dichloromethane

Procedure

TPAP (10.0 mg, 0.03 mmol) was added to a suspension of trans-2-phenyl-1-cyclohexanol (68.3 mg, 0.39 mmol), NMO (104.7 mg, 0.89 mmol) and MS4A (156 mg) in dichloromethane (2.8 mL) at room temperature and the mixture was stirred for 3 hours. After the addition of MS4A (220 mg), the reaction mixture was stirred at room temperature for overnight. Then the mixture was directly purified by column chromatography (on silica gel, ethyl acetate:hexane = 0:1 - 9:91) to give 2-phenylcyclohexanone (58.4 mg, 87% yield) as a white solid.

Experimenter’s Comments

The reaction mixture was monitored by TLC (ethyl acetate:hexane = 2:1, Rf = 0.70).
TPAP and NMO were weighed quickly due to their hygroscopicity.
MS4A was heated and dried using a heat gun under reduced pressure before use.

Analytical Data

2-Phenylcyclohexanone

¹H NMR (270 MHz, CDCl₃); δ 7.37-7.22 (m, 3H), 7.16-7.13 (m, 2H), 3.61 (dd, J = 5.4, 11.6 Hz, 1 H), 2.58-2.39 (m, 2H), 2.33-2.78 (m, 6H).

¹³C NMR (67.8 MHz, CDCl₃); δ 210.3, 138.7, 128.5 (2C), 128.3 (2C), 126.9, 57.4, 42.2, 35.1, 27.8, 25.3.

Other References

• Preparation and use of tetra-n-butylammonium per-ruthenate (TBAP reagent) and tetra-n-propylammonium per-ruthenate (TPAP reagent) as new catalytic oxidants for alcohols
• • W. P. Griffith, S. V. Ley, G. P. Whitcombe, A. D. White, J. Chem. Soc. Chem. Commun. 1987, 1625.