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Pipecolic acid-catalyzed direct asymmetric mannich reactions.

ABSTRACT: Mannich reactions between aldehydes and N-p-methoxyphenyl-protected alpha-imino ethyl glyoxylate have been performed using (S)-pipecolic acid as catalyst. The reactions give both syn- and anti-products (dr=1.4-2:1) with high enantioselectivities (>98% ee). In contrast, (S)-proline-catalyzed reactions give mainly syn-products with high enantioselectivities. Computational studies reveal that the energetic preference between the transition structures involving the s-cis-enamine and the s-trans-enamine is smaller for the pipecolic acid as compared to proline, yielding the (2S,3R)-anti and the (2S,3S)-syn Mannich product in nearly equal amounts.

SUBMITTER: Cheong PH

PROVIDER: S-EPMC3164113 | biostudies-literature | 2006 Mar

REPOSITORIES: biostudies-literature

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Pipecolic acid-catalyzed direct asymmetric mannich reactions.

Cheong Paul Ha-Yeon PH Zhang Haile H Thayumanavan Rajee R Tanaka Fujie F Houk K N KN Barbas Carlos F CF

Organic letters 20060301 5

Mannich reactions between aldehydes and N-p-methoxyphenyl-protected alpha-imino ethyl glyoxylate have been performed using (S)-pipecolic acid as catalyst. The reactions give both syn- and anti-products (dr=1.4-2:1) with high enantioselectivities (>98% ee). In contrast, (S)-proline-catalyzed reactions give mainly syn-products with high enantioselectivities. Computational studies reveal that the energetic preference between the transition structures involving the s-cis-enamine and the s-trans-enam ...[more]

PMID: 16494447

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