Proline Based Chiral Ionic Liquids for Enantioselective Michael Reaction

Table 1

Enantioselective Michael reaction of trans-β-nitrostyrene with cyclohexanone in the presence of 1a^a.

Entry	1a/mol %	Additive	Temp/°C	Yield^b/%	dr^c/syn/anti	ee^d/%
1	15	none	rt	52	92/8	85
2	15	SA^e	rt	92	92/8	87
3	15	TFA^f	rt	88	91/9	93
4	25	TFA^f	rt	92	94/6	93
5	15	TFA^f	5	60	96/4	95
6	30	TFA^f	5	84	94/6	92

All reactions were carried out using 20 equivalent ketone and 1 equivalent trans-β-nitrostyrene moieties in the presence of 1a and additive (5 mol%) under neat conditions at room temperature for 48 h. ^bIsolated yield. ^cDetermined by ¹H NMR spectroscopy. ^dDetermined by chiral HPLC analysis (CHIRALPAK AD-H). ^eSalicylic acid. ^fTrifluoroacetic acid.