Table 3. Effects of Concentrations for the Reaction of 5 and 2a to Afford 6a.
| entry | toluene (mL) | 2a (equiv; mM) | DBU (equiv; mM) | time (h) | yield of 6 (%)b |
|---|---|---|---|---|---|
| 1c | 0.5 | 1.5; 135 | 0.1; 9.0 | 2 | 76 |
| 2c | 1.0 | 1.5; 67 | 0.1; 4.5 | 3 | 94 |
| 3c | 1.0 | 1.05; 47 | 0.1; 4.5 | 2 | 96 |
a
For the reactions, to a solution of 5 (0.045 mmol, 1.0 equiv) and 2a (0.067 mmol, 1.5 equiv or 0.047 mmol, 1.05 equiv) in toluene (indicated volume), DBU (0.0045 mmol, 0.1 equiv) was added, and the mixture was heated at 60 °C.
b
Determined by 1H NMR analysis.
c
Results reported in ref (1j) are interpreted (concentrations are calculated for this study).