Proline Based Chiral Ionic Liquids for Enantioselective Michael Reaction

Table 2

Reusability of the ionic liquid catalyst 1a for enantioselective Michael reaction^a.

Cycle	Time/h	Yield^b/%	dr^c/syn/anti	ee^d/%
1	48	92	94/6	93
2	48	92	91/9	91
3	72	92	90/10	89
4	96	72	92/8	87

All reactions were carried out using 20 equivalent cyclohexanone and 1 equivalent trans-β-nitrostyrene in the presence of 1a (25 mol%) and trifluoroacetic acid (TFA) (5 mol%) under neat conditions at room temperature. ^bIsolated yield. ^cDetermined by ¹H NMR spectroscopy. ^dDetermined by chiral HPLC analysis (CHIRALPAK AD-H).