Fig. 3. Coupling of arylzinc reagents with aryl halides aided by the BDA photoredox catalysis.
The reaction was carried out under nitrogen atmosphere at 25°C for 24 hours using an arylmagnesium bromide (1: 0.56 mmol in 0.6 ml of THF), ZnCl2 (0.60 mmol in 1.4 ml of THF), an aryl halide (2, 2’, or 2”: 0.40 mmol), BDA (4.0 μmol), DMA (2.0 ml), and an LED lamp (λmax = 470 nm, 0.60 W). The yield of the isolated product is based on 2. *The yield of hydrodehalogenation products (4). †The radiated energy of the light is 0.03 W. ‡ZnBr2 was used instead of ZnCl2. §LiCl (0.60 mmol) was added. ¶1,4-Dibromobenzene (0.20 mmol) was used. #LiCl (1.6 mmol) was added. **An arylzinc iodide (1’: 0.56 mmol in THF/Tetramethylurea) with MgCl2 (1.6 mmol) was used. ††Without MgCl2. ‡‡1’k (1.12 mmol) was used in the presence of LiCl (1.6 mmol) instead of MgCl2.