Table 1.
Optimization for γ-Selective Addition of an Isatin-Derived Azadienolate to Phenylbutadienea
 | ||||||
|---|---|---|---|---|---|---|
| entry | L | NaBArF4 (Y/N) | 3a:3a′ b | conv to 3a/3a′ b (%) | dr of 3ab | er of 3ac |
| 1 | BINAP | N | 1:2.5 | 48 | 1:1 | nd |
| 2 | MeO-BIPHEP | N | 1:2.5 | 66 | 1.5:1 | nd |
| 3 | DTBM-MeO-BIPHEP | N | >20:1 | 49 | 7:1 | nd |
| 4 | SEGPHOS | N | 1:1.1 | 30 | 3:1 | nd |
| 5 | DM-SEGPHOS | N | 1:1.5 | 38 | 3:1 | nd |
| 6 | DTBM-SEGPHOS | N | >20:1 | >98 | 9:1 | 91.5:8.5 |
| 7 | DTBM-SEGPHOS | Y | >20:1 | >98 | 9:1 | 93:7 |
| 8d | DTBM-SEGPHOS | N | >20:1 | >98 | 8:1 | 94:6 |
| 9d,e | DTBM-SEGPHOS | Y | >20:1 | 97 (80)f | 8:1 | 95:5 |
a
Reactions run under N2 with 0.15 mmol of diene 2a (0.75 M).
b
Determined by 376 MHz 19F NMR spectroscopy of the unpurified mixture.
c
Determined by HPLC analysis of purified 3a.
d
1,4-Dioxane as solvent.
e
Reaction for 12 h.
f
Isolated yield of purified 3a. nd = not determined.