Table 1.

Catalyst Screening and Reaction Condition Optimizations^a

entry	catalyst	solvent	temp (°C)	time (h)	yield (%)b	ee (%)c
1	1	acetone	rt	24	—	—
2	2	acetone	rt	24	46	72
3	3	acetone	rt	3	93	84
4	3	CH2Cl2	rt	10	76	84
5	3	DMSO	rt	10	45	79
6	3	DMF	rt	10	55	60
7	3	acetone	0	10	95	92
8d	3	acetone	0	24	95	94
9d	3	acetone	-20	24	62	94
10	ent-3	acetone	0	24	91	92e

^aUnless otherwise indicated, all reactions were performed with freshly prepared diethyl formylphosphonate hydrate (4, 0.5 mmol), acetone (0.2 mL), solvent (0.4 mL) and catalyst (10 mol %) at 0 ° C.

^bYield of isolated product after column chromatography.

^cThe enantiomeric excess was determined by chiral GC analysis with a Chiraldex GTA column.

^dWith 5 mol % of catalyst loading.

^e(R)-6a was obtained as the major enantiomer.