Table 1. Optimization toward Benzotriazin-4(3H)-one 2a.
| Entrya | Solvent (mM) | Wavelength | Yield (SM%)b |
|---|---|---|---|
| 1 | MeCN (18) | 365 nm | 41 (57) |
| 2 | AcOEt (35) | 365 nm | 30 (54) |
| 3 | MeOH (38) | 365 nm | 97 |
| 4 | MeCN/H2O (2/1) (38) | 365 nm | 96 |
| 5 | DCM (50) | 365 nm | 84 |
| 6 | Acetone (35) | 365 nm | 0 (99) |
| 7 | DCM/MeOH (1/3) (50) | 365 nm | 95 |
| 8 | DCM/MeOH (1/3) (50) | 420 nm | 96c |
| 9d | DCM/MeOH (1/3) (50) | 420 nm | 68 (28) |
| 10 | DCM/MeOH (1/3) (50) | – | 0 (99) |
a
Reaction conditions: Unless otherwise specified all the reactions were performed at 0.3 mmol scale in the corresponding solvent (homogeneous solution at 22–25 °C) with a residence time of 10 min (flow rate 1 mLmin-1) using the corresponding high-power LEDs with an input power of 50 W and a system pressure of 3 bar.
b
qNMR yields were calculated using 1,3,5-trimethoxybenzene as the internal standard.
c
88% isolated yield (0.91 mmol scale).
d
5 min residence time (2 mL/min).