Table 1.
Asymmetric Henry reactions of various aldehydes with nitromethane catalysed by copper(II) complexes of ligands Ia–c.
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| Aldehyde | Ligand Ia (trans-trans) |
Ligand Ib (cis-trans) |
Ligand Ic (cis-cis) |
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| R | Conva [%] | eeb [%] | Conva [%] | eeb [%] | Conva [%] | eeb [%] |
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| Ph | 99 | 60 (R) | 99 | 38 (R) | 99 | 94 (S) |
| 4-NO2C6H4 | 99 | 29 (R) | 99 | 8 (R) | 99 | 91 (S) |
| 2-CH3OC6H4 | 99 | 80 (R) | 99 | rac | 99 | 94 (S) |
| 4-ClC6H4 | 99 | 52 (R) | 99 | 7 (R) | 99 | 95 (S) |
| 2-thienyl | 94 | 66 (R) | 99 | 20 (R) | 86 | 95 (S) |
| naphth-2-yl | 96 | 69 (R) | 94 | 25 (R) | 94 | 93 (S) |
| PhCH2CH2 | 98 | 73 (R) | 91 | 38 (R) | 95 | 89 (S) |
| t-Bu | 35 | 80 (R) | 30 | 41 (R) | 32 | 96 (S) |
| iPr | 98 | 83 (R) | 94 | 43 (R) | 99 | 91 (S) |
aThe conversion was determined by 1H NMR analysis of the crude product. bThe enantiomeric excess was determined by chiral HPLC.