Enantioselective 1,3-Dipolar Cycloadditions of Azlactones and Electrophilic Alkenes Catalyzed by Dimeric BinapAuTFA Complexes

Abstract

Glycine-derived azlactones react with maleimides using (S)- or (R)-dimeric BinapAuTFA complexes affording the corresponding cycloadducts in good yields and high enantioselections (up to 99% ee). The intermediate carboxylic acids are treated with trimethylsilyldiazomethane and isolated as Δ^¹-pyrroline methyl esters. These cycloadducts are transformed into exo-proline derivatives by reduction with NaBH₃CN in acidic media. On the other hand, N-benzoylalanine-derived oxazolone reacts with tert-butyl acrylate providing the cycloadduct with the ester group at the 3-position with a trans-relative configuration with respect to the methyl ester group.

Key words

gold - Binap - cycloaddition - azomethine ylides - asymmetric catalysis

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  Martín-Rodríguez, M.; Nájera, C.; Sansano, J. M.; de Cózar, A.; Cossío, F. P. submitted for publication

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For the typical procedure and data of the isolated products, see Supporting Information.