Table 3.
Screening of reaction times using F8BT-based polymer 2-S as starting polymer.
| Starting polymer | DMDO [equiv] | Reaction time | Result (analysis by 1H NMR spectroscopy, also see Figure 6) |
|---|---|---|---|
| 2-S | 2.5 | 0 min | Incomplete oxidation |
| 2-S | 2.5 | 5 min | Complete and selective oxidation to 2-SO2 |
| 2-S | 2.5 | 1 h | Complete and selective oxidation to 2-SO2 |
| 2-S | 3.0 | 24 h | Complete and selective oxidation to 2-SO2 (no byproduct signals) |
| 2-F | 2.5 | 5 min | No reaction, no change of 1H NMR spectrum |
Final conditions for the synthesis of 2-SO2 highlighted in gray. The selectivity was investigated by treating 2-S with a large excess of DMDO for prolonged time (3.0 equiv, 24 h) and by control experiments using 2-F. Reaction procedure: DMDO in acetone (0.104 M) added to stirred polymer solutions in chlorobenzene (concentration of repeat unit: 0.01 M) at room temperature. Work-up: evaporation of solvents (and excessive DMDO) under reduced pressure at 50°C.