Table 1.

Michael addition of diphenyl phosphite (2) to trans-β-nitrostyrene (1a) catalyzed by 4 or 5^[a].

entry	catalyst	time	conv [%][b]	ee [%]
1	4a	45 min	98	81
2	4b	1 h	96	84
3	4c	30 min	98	88
4	4d	30 min	97	95
5	5	15 min	99	96

^[a]Reactions were carried out on 0.20 mmol of 1a with 1.25 equiv of 2 and 10 mol% 4 or 5 in 1.0 mL CH₂Cl₂ at room temperature.

^[b] Reaction conversions were determined by ¹H-NMR.