Optimization of reaction conditions^a.

Entry	Base	Solvent	trans : cisb	Combined yield (%)c
1	K2CO3	CH3CN	72 : 28	78
2	KOtBu	CH3CN	70 : 30	16
3	KOAc	CH3CN	73 : 27	34
4	K3PO4·3H2O	CH3CN	71 : 29	87
5	DABCO	CH3CN	72 : 28	44
6d	K3PO4·3H2O	CH3CN	71 : 29	46
7e	K3PO4·3H2O	CH3CN	70 : 30	57
8	K3PO4·3H2O	Toluene	54 : 46	6
9	K3PO4·3H2O	CH2Cl2	58 : 42	33
10	K3PO4·3H2O	ClCH2CH2Cl	59 : 41	40
11	K3PO4·3H2O	THF	80 : 20	54
12	K3PO4·3H2O	Acetone	61 : 39	11
13	K3PO4·3H2O	AcOEt	56 : 44	44
14	K3PO4·3H2O	CHCl3	76 : 24	4
15f	K3PO4·3H2O	CH3CN	72 : 28	93

^aUnless otherwise specified, all reactions were carried out using N-tert-butylsulfinyl imine 1a (0.20 mmol) and sulfur ylide precursor 2a (0.50 mmol, 2.5 equiv.) in 2 mL solvent with 0.50 mmol of base at room temperature.

^bDetermined by ¹H NMR (crude reaction mixture).

^cCombined yield of isolated products of trans-3a and cis-3a after column chromatography.

^dK₃PO₄·3H₂O loading is 0.10 mmol.

^eK₃PO₄·3H₂O loading is 0.40 mmol.

^fThe reaction temperature is 30 °C.