Table 2 In situ NMR analysis of methylating reagents
From: Leveraging long-lived arenium ions in superacid for meta-selective methylation
Entry | Reagent (conditions) | Experimental δ 1H (ppm) | Experimental δ 13C (ppm) | DFT calculateda δ 13C (ppm) | ||
|---|---|---|---|---|---|---|
1 | Me2SO4 (HF/SbF5, −50 °C) | 3.11 | 66.4 | 64.8 | ||
2 | Me2SO4 (Acetone-d6, 20 °C) | 3.98 | 59.4 | 54.8 | ||
3 | Me3PO4 (HF/SbF5, −50 °C) | 2.66 (d, J = 11.5 Hz) | 57.7 (d, J = 7.5 Hz) | 58.5 (d, J = 7.2 Hz) | ||
4 | Me3PO4 (Acetone-d6, 20 °C) | 3.71 (d, J = 11.0 Hz) | 54.4 (d, J = 5.9 Hz) | 53.4 (d, J = 6.4 Hz) | ||
5 | MeOTf (HF/SbF5, −50 °C) | 3.56 3.48 | 71.8 70.4 | 117.3 (q, J = 324 Hz) 117.1 (q, J = 321 Hz) | 71.1b 69.8c | 127.4 (q, J = 370 Hz)b 127.3 (q, J = 369 Hz)c |
6 | MeOTf (CD2Cl2, 20 °C) | 4.22 | 62.6 | 119.1 (q, J = 319 Hz) | 60.2 | 127.1 (q, J = 366 Hz) |
Proposed structures of methylating reagents in HF/SbF5 | ||||||
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