Organocatalyzed aldol reaction of acetone with phenylglyoxylic acid^a.

Entry	Cat	T	% convb	e. r.c
1	4	NO	93	75 : 25
2	6a	NO	54	89 : 11
3	6b	NO	85	92 : 8
4	4	YES	100	60 : 40
5	6b	YES	38	72 : 28

^aReaction conditions: acetone (0.25 mmol), phenylglyoxylic acid (0.025 mmol), catalyst (10 mol%), N-hexylthymine (0 or 0.125 mmol), CH₂Cl₂ (100 μL), 25 °C, 2 days.

^bDetermined by ¹H NMR from the crude reaction.

^ce. r. determined by HPLC using a Daicel ChiralPak AS-H column. For analytical reasons, the adduct 12 was derivatized to its methyl ester (see the ESI).