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Asymmetric Synthesis of 3,4‐Dihydrocoumarins Bearing an α,α‐Disubstituted Amino Acid Moiety
Authors:Joanna Hejmanowska  Anna Albrecht  Jakub Pi&#x;ta  &#x;ukasz Albrecht
Abstract:An organocatalytic approach for the stereoselective synthesis of 3,4‐dihydrocoumarins with an α,α‐disubstituted amino acid moiety incorporated is presented. The developed methodology is based on the cascade reaction between α‐substituted azlactones and 2‐hydroxychalcones. It is initiated by a chiral Brønsted base‐catalyzed enantio‐ and diastereoselective Michael reaction followed by the azlactone ring opening to construct a 3,4‐dihydrocoumarin framework. Products bearing two adjacent stereogenic centers, one being quaternary, were formed with high enantioselectivities and excellent diastereoselectivities. Furthermore, the complete regioselectivity of the new cascade reactivity is worthy of notice.
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Keywords:azlactones  cascade reactions  3  4‐dihydrocoumarins  α    α  ‐disubstituted amino acids  organocatalysis
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