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C-H Activation of Methyl Arenes in the MnO2-Mediated Aroylation of N-Chlorosulfoximines

Daniel L. Priebbenow and Carsten Bolm*

*Institute of Organic Chemistry, RWTH Aachen University, Landoltweg 1, D-52074 Aachen, Germany, Email: carsten.bolmoc.rwth-aachen.de

D. L. Priebbenow, C. Bolm, Org. Lett., 2014, 16, 1650-1652.

DOI: 10.1021/ol5003016

Abstract

A method for the synthesis of N-aroylated sulfoximines involves a manganese oxide promoted C-H activation of methyl arenes to form an aroyl intermediate which then reacts readily with N-chlorosulfoximines to form a series of valuable aroyl sulfoximine derivatives in high yields.

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General Procedure 1 for synthesis of N-aroylated sulfoximines:

To a solution of N-chlorosulfoximine (0.50 mmol) in acetonitrile (2 mL) was added methyl arene (5.0 mmol), TBHP (70% in H2O, 2.0 mmol, 4.0 equiv.) and MnO2 (43.5 mg, 0.50 mmol, 1.0 equiv.). The reaction mixture was stirred at 80°C for 48 hours. After this time, the contents were cooled to room temperature, filtered over a pad of silica, which was subsequently washed with ethyl acetate. The filtrate was evaporated under reduced pressure to afford the product, which was then purified by silica gel column chromatography using pentane/ethyl acetate (2:1) as eluent. Where possible, the product was further purified by vapour diffusion crystallization using CH2Cl2/pentane.

General Procedure 2 for synthesis of N-aroylated sulfoximines:

N-Chlorosuccinimide (0.60 mmol) was added to a solution of NH-sulfoximine (0.50 mmol) in acetonitrile (2 mL) and stirred at room temperature for 2 hours. To this solution was then added methylarene (5.0 mmol), TBHP (70% in H2O, 2.0 mmol, 4.0 equiv.) and MnO2 (43.5 mg, 0.50 mmol, 1.0 equiv.). The reaction mixture was stirred at 80 °C for 48 hours. After this time, the contents were cooled to room temperature, filtered over a pad of silica, which was subsequently washed with ethyl acetate. The solvent was evaporated under reduced pressure to afford the product, which was then purified by silica gel column chromatography using pentane/ethyl acetate (2:1) as eluent. Where possible, the product was further purified by vapour diffusion crystallization using CH2Cl2/pentane.

Key Words

sulfoximines, MnO2, TBHP, NCS

ID: J54-Y2014