Table 2. Effect of 1 equiv of Base on 1H NMR (600 MHz, CDCl3, 25 °C) Nonequivalences (ppm) for 5 (30 mM) in the Presence of 1 equiv of 1-TU.
| base |
|||
|---|---|---|---|
| proton | DABCO | DMAP | NBu4+ |
| o-DNB | 0.129 | 0.140 | 0.088 |
| p-DNB | 0.079 | 0.081 | 0.052 |
| NH | 0.010 | 0.040 | 0.028 |
| CH | 0.034 | 0.009 | 0.022 |