Table 1.

Substrate scope of L-proline catalyzed aldol reactions of 2, 3-diketoesters with cycloketones.^a

Entry	R1	R2	X	Time	Ratio 3/4b	Yieldc (eed) of 3	Yieldc (eed) of 4
1	Me	Bn	CH2	24 h	74/26	3a/68% (99%)	4a/24% (97%)
2	Me	Me	CH2	32 h	79/21	3b/60% (99%)	4b/16% (97%)
3	Me	Cy	CH2	48 h	77/23	3c/67% (99%)	4c/20% (98%)
4	Et	Me	CH2	32 h	77/23	3d/65% (99%)	4d/19% (97%)
5	Bn	Bn	CH2	48 h	73/27	3e/59% (99%)	4e/21% (98%)
6	C6H5	Et	CH2	32 h	81/19	3f/51% (99%)	4f/12% (98%)
7	p-ClC6H4	Et	CH2	48 h	89/11	3g/58% (99%)	4g/7% (94%)
8	p-BrC6H4	Et	CH2	48 h	89/11	3h/56% (99%)	4h/6% (95%)
9	p-OMeC6H4	Et	CH2	96 h	85/15	3i/25% (99%)	4i/4% (98%)
10	p-CNC6H4	Et	CH2	42 h	84/16	3j/70% (99%)	4j/13% (96%)
11	2-naphthyl	Et	CH2	54 h	79/21	3k/45% (99%)	4k/12% (97%)
12	2-thienyl	Et	CH2	48 h	88/12	3l/67% (99%)	4l/9% (92%)
13	Me	Bn	S	48 h	76/24	3m/56% (99%)	4m/17% (89%)

^aReaction conditions:1 (1.0 mmol), 2 (2.0 mmol), L-proline (20 mol%), DCM (5.0 mL), rt, 24–96 h.

^bDetermined by ¹H NMR spectroscopy or HPLC analysis of the reaction mixture.

^cYield of the isolated product after column chromatography.

^dThe ee value was determined by HPLC using a chiral stationary phase.