Table 1. Optimizing the Reaction Conditions.
| entry | variationsa | dark reaction | 1H NMR yield (%) of 5 (o:p) |
|---|---|---|---|
| 1 | – | – | 56 (1:2) |
| 2 | no acid | – | 0 |
| 3 | under N2 | – | 22 (1:1) |
| 4b | – | yes | 51 (1:2) |
| 5c | Ru(bpy)3Cl2·6H2O | – | 81 (1.2:1) |
| 6c | Eosin Y | – | 39 (1:2) |
| 7c | [Ir(dtbbpy)(ppy)2]PF6 | – | 32 (1:2) |
| 8c | Ru(bpy)3Cl2·6H2O under N2 | – | 9 (1.5:1) |
| 9c | Ru(bpy)3Cl2·6H2O under N2 | yes | 11 (1.4:1) |
| 10c | Ru(bpy)3Cl2·6H2O without acid | yes | 0 |
a
All reactions were conducted on a 0.0613 mmol scale in d3-acetonitrile, at room temperature, open to air, and at a concentration of 0.1 M, unless stated otherwise.
b
The reaction was carried out in an amber HPLC vial in a blacked out box (including the addition of acid).
c
In cases in which an additive was used, the additive is listed under “variations” and was used at a 2 mol % level.