Table 1.
Optimization and control studies.a
| entry | catalyst (mol%) | O2 | concn (M) | temp (°C) | yield (3/4)b |
|---|---|---|---|---|---|
| 1c | Ru(bpz)3(PF6)2 (5) | 1 atm | 0.1 | 23 | 29%/30% |
| 2c | Ru(bpz)3(PF6)2 (5) | 3 atm | 0.1 | 23 | 22%/35% |
| 3c | Ru(bpz)3(PF6)2 (5) | 4 atm | 0.1 | 23 | 16%/44% |
| 4c | Ru(bpz)3(PF6)2 (5) | 4 atm | 0.05 | 23 | 16%/49% |
| 5 | Ru(bpz)3(PF6)2 (5) | 4 atm | 0.02 | 23 | 11%/77% |
| 6 | Ru(bpz)3(PF6)2 (5) | 4 atm | 0.02 | 5 | <5%/79% |
| 7 | Ru(bpz)3(PF6)2 (0.5) | 4 atm | 0.02 | 5 | <5%/75%d |
| 8 | Ru(bpy)3(PF6)2 (0.5) | 4 atm | 0.02 | 5 | <5%/<5% |
| 9 | tetraphenylporphyrin (5) | 4 atm | 0.02 | 5 | <5%/<5% |
| 10 | 9,10-dicyanoanthracene (5) | 4 atm | 0.02 | 5 | <5%/<5% |
| 11 | triphenylpyrylium•BF4 (5) | 4 atm | 0.02 | 5 | <5%/20% |
a
Reactions were conducted in a 135 mL glass pressure vessel and irradiated for 30 min with a 200 W incandescent light bulb unless otherwise noted.
b
Yields determined by 1H NMR spectroscopy using an internal standard, unless noted.
c
Irradiated for 2 h.
d
Isolated yield.