Table 1.
Optimization of the reaction conditions under photo-initiated conditions
| ||
|---|---|---|
| Alternation from above conditions | 2a conv. | 3a yield |
| None | 100% | 96% (92%) |
| No I2 | 0% | ND |
| No Ru(bpy)3Cl2 | 0% | ND |
| White light instead of blue light | 95% | 85% |
| In the dark | 0% | ND |
| Ir(dtbbpy)(bpy)2PF6 instead of Ru(bpy)3Cl2 | 75% | 65% |
| Eosin Y instead of Ru(bpy)3Cl2 | 0% | ND |
| 10 mol% 1a′ instead of I2 | 100% | 94% |
| 10 mol% Br2 instead of I2 | 0% | ND |
| No I2, 1 equiv. of 1a′ instead of 1a | <5% | Trace |
| No I2, 1 equiv. of 1a′ instead of 1a i-Pr2EtN (1 equiv.), Na2S2O3 (1 equiv.), MeCN instead of DCE (Suero’s condition, Ref. 22) |
55% | 35% |
| Addition of 1 equiv. of TEMPO | 0% | ND |
Reaction conditions: 1 mol% photocatalyst and 10 mol% I2 were added to a DCE (3 mL) solution of 2a (0.3 mmol) and EDA 1a (0.3 mmol), and reaction was kept under argon (degassed) at room temperature under blue light for 24 h. Conversion and yield were determined by 1H NMR spectroscopy using 1,3,5-trimethoxybenzene as internal standard. Isolated yield are given within parentheses.
EDA ethyl diazoacetate, DCE 1,2-dichloroethane, r.t. room temperature, 1H NMR proton nuclear magnetic resonance, TEMPO (2,2,6,6-tetramethylpiperidin-1-yl)oxyl or (2,2,6,6-tetramethylpiperidin-1-yl)oxidanyl, ND not determined