Table 1.

Optimization of the Michael reaction.

Entry	Catalyst	Conditions[a]	Yield[b]	ee [%][c]
1	A	DBU, THF	6	–
2	A	KN(SiMe3)2, THF[d]	11	–
3	A	iPr2EtN, THF, 45°C	50	–
4	B	iPr2EtN, toluene/THF[e]	61	–
5	C	iPr2EtN, toluene/THF[e,f]	61	93
6	C	Et3N (0.1 m), toluene/THF[e]	62	93
7	C	iPr2EtN (0.1 m), CH2Cl2, −20°C	49	93
8	D	iPr2EtN (0.1 m), toluene/THF[e]	53	99
9	D	iPr2EtN (0.05 m), toluene/THF[e]	66	99
10	D	iPr2EtN (0.05 m), CH2Cl2	68	99
11	D[g]	iPr2EtN (0.05 m), CH2Cl2	68	99

^[a]Base (20 mol %), 1a (0.2 m) at 23°C unless otherwise noted. DBU = 1,8-diazabicyclo[5.4.0]undec-7-ene.

^[b]Yield of isolated product.

^[c]Determined by HPLC (Chiracel AD-H). Absolute and relative configuration of 3 assigned by X-ray crystallography.[16] See the Supporting Information for details.

^[d]Carbene generated prior to addition of substrate.

^[e]10:1 toluene/THF.

^[f]Base (1.2 equiv).

^[g]D (10 mol %).