Model Michael addition in homogeneous environment catalyzed with Ia–Id under the optimized conditionsa.
| Entry | Catalyst | Reaction time [h] | Conversionb (isol. yieldc) [%] | eed [%] | syn : antib |
|---|---|---|---|---|---|
| 1 | Ia | 48 | 94 (87) | 91 | 95 : 5 |
| 2 | Ib | 72 | Quant. (91) | 94 | 94 : 6 |
| 3 | Ic | 48 | 0 | — | — |
| 4 | Id | 5 | Quant. (79) | 84 | 95 : 5 |
| 5 | Id (10 mol%) | 48 | Quant. (85) | 92 | 97 : 3 |
| 6 | Id (5 mol%) | 120 | 50 (42) | 93 | 95 : 5 |
| 7 | Id (2 mol%) | 120 | 7 (4) | 93 | 96 : 4 |
a
Reaction conditions: nitrostyrene 0.25 mmol, cyclohexanone 1 ml, catalyst 0.05 mmol, acetic acid 0.035 mmol, solvent 1 ml, t = 25 °C.
b
Determined by 1H NMR.
c
Purified by column chromatography (hexane : ethyl acetate = 5 : 1).
d
Determined by chiral HPLC (column YMC amylose C, mobile phase heptane : IPA = 9 : 1, flow rate 0.7 ml min−1).