Copper-Catalyzed Oxidative Electrophilic Carbofunctionalization of Acrylamides for the Synthesis of Oxindoles

Abstract

A novel and efficient copper-catalyzed tandem oxidative cyclization of arylacrylamides with diaryliodonium salts is reported. This reaction provides a novel approach for the synthesis of oxindoles and various functional groups were well tolerated.

Key words

copper-catalyzed - acrylamides - diphenyliodonium ­triflate - oxindoles - electrophilic arylation

• References and Notes


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• 10 Typical Procedure: An oven-dried 10-mL Schlenk tube containing CuCl (4.5 mg, 15 mol%), N-arylacrylamide 1a (90.3 mg, 0.3 mmol), and diphenyliodonium triflate (2a; 154.8 mg, 0.36 mmol) was evacuated and purged with nitrogen three times. DTBP (68.8 mg, 0.36 mmol) in freshly distilled CH₂Cl₂ (2.0 mL) was added to the system at r.t. The reaction mixture was heated with stirring at 60 °C for 24 h. The reaction mixture was allowed to cool to ambient temperature, and then transferred to a round-bottom flask. Silica gel (3.0 g) was added, and the solvent was removed under reduced pressure to afford a free-flowing powder. This powder was then dry-loaded onto a silica gel column and purified by flash chromatography using petroleum ether–EtOAc (20:1) as the eluent to give the product 3a. Yield: 75 mg (81%). MS (ESI): m/z = 274.0 [M + Na]⁺. ¹H NMR (400 MHz, CDCl₃): δ = 7.03–7.18 (m, 6 H), 6.83–6.85 (m, 2 H), 6.62 (d, J = 7.7 Hz, 1 H), 3.12 (d, J = 13.0 Hz, 1 H), 3.01 (d, J = 13.0 Hz, 1 H), 2.98 (s, 3 H), 1.47 (s, 3 H). ¹³C NMR (100 MHz, CDCl₃): δ = 179.9, 142.9, 136.0, 132.9, 129.7, 127.6, 126.3, 123.2, 121.9, 107.6, 50.0, 44.4, 26.7, 22.6.