Proline Based Chiral Ionic Liquids for Enantioselective Michael Reaction

Table 3

Enantioselective Michael reaction of various trans-β-nitrostyrene derivatives with several ketones and an aldehyde in the presence of 1a^a.

Entry	R1	R2	R3	Yield^b/%	dr^c/syn/anti^c	ee^d/%
1	–(CH2)4–		Ph	92	94/6	93
2	–(CH2)4–		4-CH3O–Ph	92	94/6	95
3	–(CH2)4–		4-Cl–Ph	96	92/8	90
4	–(CH2)4–		2-furyl	85	87/13	89
5	–(CH2)4–		2-thienyl	83	85/15	86
6	–(CH2)3–		Ph	79	62/38	68
7	–(CH2)3–		4-CH3O–Ph	79	71/29	70
8	CH3	H	H	92	—	24
9^e	H	CH(CH3)2	H	12	86/14	68

All reactions were carried out using 20 equivalent ketone and 1 equivalent trans-β-nitrostyrene moieties in the presence of 1a (25 mol%) and trifluoroacetic acid (TFA) (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) according to references [22–24]. ^eAmount of 1a was 15 mol% and reaction time was 7 days.