Enantioselective aldol reactions with aqueous 2,2-dimethoxyacetaldehyde organocatalyzed by binam-prolinamides under solvent-free conditions |
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| Institution: | 1. A. I. Herzen State Pedagogical University of Russia, 191186 St. Petersburg, Russian Federation;2. Department of Crystallography, St. Petersburg State University, 199034 St. Petersburg, Russian Federation;1. Key Laboratory for Advanced Materials and Institute of Fine Chemicals, East China University of Science & Technology, Shanghai 200237, PR China;2. Division of Theoretical Chemistry & Biology, School of Biotechnology, KTH Royal Institute of Technology, SE-10691 Stockholm, Sweden;3. Key Laboratory of Photochemical Conversion and Optoelectronic Materials, Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Beijing 100190, PR China |
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| Abstract: | Aqueous 2,2-dimethoxyacetaldehyde (60% wt solution) is used as an acceptor in aldol reactions, with cyclic and acyclic ketones and aldehydes as donors, organocatalyzed by 10 mol % of N-tosyl-(Sa)-binam-l-prolinamide (Sa)-binam-sulfo-l-Pro] at rt under solvent-free conditions. The corresponding monoprotected 2-hydroxy-1,4-dicarbonyl compounds are obtained in good yields and with high levels of diastereo- and enantioselectivity mainly as anti-aldols. In the case of 4-substituted cyclohexanones a desymmetrization process takes place to mainly afford the anti,anti-aldols. 2,2-Dimethyl-1,3-dioxan-5-one allows the synthesis of a useful intermediate for the preparation of carbohydrates in higher yield, de and ee than with l-Pro as the organocatalyst. |
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