We have demonstrated that a new class of l-proline-based organic compounds catalyzed the direct aldol reaction between aldehydes and acetone to provide beta-hydroxy ketones in good yields. The reaction is efficient, and 5-10 mol % of the catalyst and excellent enantioselectivities (97-99% ee) were obtained in both aromatic and aliphatic aldehydes. The presence of a gem-diphenyl group at the beta-carbon is necessary for high enantioselectivity.

A chiral diamine was found to catalyze enantioselective addition of ketones to nitroolefins in aqueous/saline/organic media. The products were obtained with excellent diastereoselectivities (syn/anti = 99:1) and enantioselectivities up to 99%. The reaction could be facilitated using a mild acid. [reaction: see text]

To clarify anomalies in the HPLC traces for compound 2b (Table 2, entry 2), the experiments were redone under similar conditions and subjected to HPLC. The new HPLC traces so obtained are provided in the accompanying Supporting Information.

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