Table 1. Optimization of the Reaction Conditions for the Synthesis of Thioethers via Thiol–Yne Click Reaction in the Aqueous Mediumc.
| entry | solventa | initiator (mol %) | additive (mol %) | external stimulus | time (min) | yields (%)b |
|---|---|---|---|---|---|---|
| 1 | H2O | TBHP (1.0) | FeCl3 (0.5) | sunlight | 30 | 77 |
| 2 | H2O | TBHP (1.0) | FeSO4 (0.5) | sunlight | 30 | 71 |
| 3 | H2O | TBHP (1.0) | Fe(NO3)3 (0.5) | sunlight | 30 | 72 |
| 4 | H2O | TBHP (1.0) | CuCl (0.5) | sunlight | 30 | 78 |
| 5 | H2O | FeCl3 (0.5) | sunlight | 30 | ND | |
| 6 | H2O | FeSO4 (0.5) | sunlight | 30 | ND | |
| 7 | H2O | Fe(NO3)3 (0.5) | sunlight | 30 | ND | |
| 8 | H2O | CuCl (0.5) | sunlight | 30 | ND | |
| 9 | H2O | TBHP (1.0) | sunlight | 30 | 85 | |
| 10 | H2O | H2O2 | sunlight | 30 | 10 | |
| 11 | H2O | DTBP | sunlight | 30 | 80 | |
| 12 | DMF | TBHP (1.0) | sunlight | 30 | 91 | |
| 13 | THF | TBHP (1.0) | sunlight | 30 | 92 | |
| 14 | dioxane | TBHP (1.0) | sunlight | 30 | 89 | |
| 15 | H2O | TBHP (0.5) | sunlight | 30 | 83 | |
| 16 | H2O | TBHP (0.1) | sunlight | 30 | 83 | |
| 17 | H2O | TBHP (0.05) | sunlight | 30 | 91 | |
| 18 | H2O | TBHP (0.05) | UV light | 30 | 90 | |
| 19 | H2O | TBHP (0.05) | dark condition | 30 | <10 | |
| 20 | H2O | TBHP (0.05) | TEMPO (0.5) | sunlight | 30 | ND |
a
The reaction was performed using 0.46 mmol 1a (1 equiv) and 1.0 mmol 2a (2.2 equiv) under sunlight.
b
Yields of purified compounds.
c
ND = not detected, DMF = N,N-dimethylformamide, THF = tetrahydrofuran.