Table 1.
Condition Survey for [3 + 2] Cycloaddition Leading to Bicyclic Acetals
 | ||||
|---|---|---|---|---|
| Entry | Photosensitizer (PS) | Solvent | DHP (Eq.) | Yield (%) |
| 1 | PS-A | DCE | 1 | 25 |
| 2 | PS-A | DCE | 4 | 95 (81) |
| 3 | PS-B | DCE | 4 | 10 |
| 4 | PS-C | DCE | 4 | 5 |
| 5 | Ru(bpy)3Cl2 | DCE | 4 | 0 |
| 6 | Ir[dF(CF3)ppy]2(dtbbpy)PF6 | DCE | 4 | 0 |
| 7 | PS-A | MeCN | 4 | 35 |
| 8 | PS-A | toluene | 4 | 0 |
| 9 | PS-A | DMF | 4 | 0 |
Unless otherwise specified, reactions were performed using photosensitizer (0.01 mmol, 5 mol%), PhSSPh (0.04 mmol, 20 mol%), cinnamyl alcohol (0.2 mmol), dihydropyran (DHP) in 3 mL of solvent. Yield of 1 was determined by GC using n-decane as internal standard. Number in parentheses is isolated yield.