Table 4.
Optimization of the Non-Phenolic Oxidative Coupling on the Model Substrate 35
| Oxidant (equiv) | Lewis Acid (equiv) | Temp (Time) | Solvent | Results | ||
|---|---|---|---|---|---|---|
| % Yield | M:P | |||||
| 1 | PIFA (0.6) | BF3·Et2O (2.5 equiv) | 0 °C - rt (2 h) | DCM | nd | nd |
| 2 | PIFA (1.02) | BF3·Et2O (4 equiv) | 0 °C - rt (8 h) | DCM | 11 | 3 : 2 |
| 3 | PIFA (1.02) | BF3·Et2O (4 equiv) | −0 °C - rt (1.5 h) | DCM | 20 | 3 : 2 |
| 4 | PIFA (0.8) | BF3·Et2O (3 equiv) | −40 °C (0.5 h) | DCM | 30 | 4 : 1 |
| 5 | PIFA (0.8) | BF3·Et2O (3 equiv) | −78 °C (0.5 h) | DCM | 25a | 4 : 1 |
| 6 | PIDA (0.8) | BF3·Et2O (3 equiv) | −40 °C (2.5 h) | DCM | nd | nd |
| 7 | Tl(OCOCF3)3 (0.8) | BF3·Et2O (3 equiv) | rt (15 min) | MeCN | nd | nd |
| 8 | Tl(OCOCF3)3 (0.8) | BF3·Et2O (3 equiv) | −40 °C (20 min) | MeCN | 38 | 2 : 3 |
| 9 | Tl(OCOCF3)3 (0.5) | BF3·Et2O (2.5 equiv) | −78 °C (40 min) | MeCN | 30 | 3 : 7 |
| 10 | Tl(OCOCH3)3 (0.7) | BF3·Et2O (3 equiv) | −40 °C (1.25 h) | MeCN | 67a | 3 : 7 |
PIFA: phenyliodine(III) bis(trifluoroacetate); PIDA: Phenyliodine(III) diacetate.
a
The yield is based on recovered starting material 36.
%Yield is based on isolation of both the diasteromers.
nd: not determined.