Table 2. Chiral proton-catalyzed Michael addition of nitroethane to β-nitrostyrenes.

Entry a	R	6	dr b	Yield c (%)	ee d (%)
1	Ph	a	20 : 1	85	94
2	2-MeO-C6H4	b	20 : 1	94	92
3	3-MeO-C6H4	c	20 : 1	85	93
4	4-MeO-C6H4	d	20 : 1	81	95
5	3,4-(MeO)2-C6H3	e	20 : 1	83	93
6	4-Me-C6H4	f	20 : 1	88	95
7	2-F-C6H4	g	20 : 1	85	94
8	4-F-C6H4	h	20 : 1	88	95
9	2-Cl-C6H4	i	20 : 1	88	95
10	3-Cl-C6H4	j	18 : 1	80	97
11	4-Cl-C6H4	k	20 : 1	80	96
12	3-Br-C6H4	l	15 : 1	78	97
13	4-CF3O-C6H4	m	20 : 1	81	94
14	1-Naphthyl	n	20 : 1	93	95
15	2-Naphthyl	o	20 : 1	88	95
16	2-Furanyl	p	9 : 1	82	85
17	PhCH2CH2	q	10 : 1	80	90
18	iPr	r	11 : 1	25	91

^aAll reactions were performed on a 0.30 mmol scale (0.2 M) using nitroethane (20 equiv.) and a standard 45 h reaction time at –20 °C.

^bMeasured by ¹H NMR.

^cIsolated yield.

^dEnantiomeric ratios were measured by HPLC using a chiral stationary phase. See ESI for details.