Intermolecular alkene difunctionalization is an effective method for rapidly increasing molecular complexity with two valuable groups. We report a strategy for the photocatalytic radical-mediated desulfonylative carboarylation of alkenes by using strategically designed arylsulfonyl acetates as both arylating and carbonylating reagents. By using an Ir complex as a photocatalyst, aryl and carbonyl groups were simultaneously incorporated into alkenes to afford synthetically useful derivatives under mild reaction conditions. This transformation is characterized by a broad substrate scope and good functional-group compatibility.
107-Methoxy-7-oxo-4-phenylheptyl 4-Methoxybenzoate (3a); Typical Procedure
The reaction was conducted in 16 mL test tube sealed with a PTFE/rubber septum. Methyl (phenylsulfonyl)acetate (1a) (0.12 mmol), CeCl3 (0.01 mmol), and Na2CO3 (0.15 mmol) were combined in anhyd DMF (0.5 mL) under N2, and a solution of TBACl (0.02 mmol) in H2O (0.1 mL) was added. The test tube was sealed and the mixture was stirred at r.t. for 1 h. A solution of pent-4-en-1-yl 4-methoxybenzoate (2a) in DMF (0.4 mL) was added under N2, and the test tube was rapidly purged with N2 (×3) then sealed and placed in a reaction bath equipped with a Kessil 440 nm blue LED (100% intensity) at a distance of 2 cm. The mixture was stirred and irradiated at rt for 16–20 h until the reaction was complete (TLC; EtOAc–hexane, 1:5), then diluted with EtOAc (15 mL) and washed with H2O (3 × 15 mL). The organic layer was dried (Na2SO4), filtered, and concentrated under reduced pressure. The residue was purified by flash column chromatography [silica gel, EtOAc–hexane (1:5 to 1:10)] to give a colorless oil; yield: 18.5 mg (50%)
1H NMR (600 MHz, CDCl3): δ = 7.98–7.92 (m, 2 H), 7.30 (t, J = 7.5 Hz, 2 H), 7.24–7.18 (m, 1 H), 7.17–7.12 (m, 2 H), 6.94–6.88 (m, 2 H), 4.21 (td, J = 6.5, 1.2 Hz, 2 H), 3.86 (s, 3 H), 3.61 (s, 3 H), 2.58 (tt, J = 9.9, 5.0 Hz, 1 H), 2.21–2.09 (m, 2 H), 2.09–2.00 (m, 1 H), 1.93–1.83 (m, 1 H), 1.84–1.77 (m, 1 H), 1.76–1.69 (m, 1 H), 1.69–1.61 (m, 1 H), 1.62–1.53 (m, 1 H). 13C NMR (126 MHz, CDCl3): δ = 174.2, 166.5, 163.4, 144.0, 131.7, 128.7, 127.8, 126.6, 123.0, 113.7, 113.7, 64.7, 55.6, 51.6, 45.3, 33.2, 32.3, 32.0, 27.0. HRMS (ESI+): m/z [M + H]+ calcd for C22H27O5: 371.1853; found: 371.1858.