Highly diastereo- and enantioselective direct aldol reactions of cycloketones with aldehydes catalyzed by a trans-4-tert-butyldimethylsiloxy-l-proline amide

An organocatalyst derived from trans-4-hydroxy-l-proline and (1S,2S)-1,2-diphenyl-2-aminoethanol catalyzes the direct aldol reactions of cycloketones with a wide scope of aldehydes in high yields and with excellent diastereoselectivities of up to >99:1 and enantioselectivities of up to >99% ee.

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(2S,1′S,2′S)-Pyrrolidine-4-trans-TBS-protected hydroxy-2-carboxylic acid (2-hydroxy-1,2-diphenyl-ethyl)-amideC25H37N2O3Si[α]D20=-17.2 (c 0.5, CH2Cl2)Source of chirality: asymmetric synthesis