An organocatalytic asymmetric vinylogous Michael addition of dicyanoolefins to vinylogous imine intermediates generated in situ from arenesulfonylalkylindoles has been developed. This protocol provides an easy and convenient approach to C-3 alkyl-substituted indole derivatives with high yields (up to 93%), diastereomeric ratios (up to 99:1 dr) and enantioselectivities (up to 99% ee). The resulting adducts can be also readily converted to pyrazolo derivatives or a-alkylation products of ketones without any decrease of the diastereoselectivities and enantioselectivities.
Enantioselective Michael addition of oxazolones to in situ generated vinylogous imine intermediates is reported. A series of optically active 3-alkylindole derivatives with adjacent quaternary and tertiary stereocenters was obtained. The[a] Chemical Synthesis and Pollution 456 resulting adducts can readily be converted into syn-configured α,β-disubstituted tryptophan derivatives without compromising the stereoselectivities.
Organocatalytic Asymmetric Michael Addition of Oxazolones to Arylsulfonyl Indoles: Facile Access to syn-Configured α,β-Disubstituted Tryptophan Derivatives. -For the first time the highly stereoselective title Michael addition reaction is presented. The resulting adducts [e.g.(III)] with quaternary and tertiary stereocenters can be readily converted into syn-configured α,β-disubstituted tryptophan derivatives [cf. (IV)] without a decrease in dia-and enantioselectivities. -(CAI, C.-W.; ZHU, X.-L.; WU, S.; ZUO, Z.-L.; YU, L.-L.; QIN, D.-B.; LIU, Q.-Z.; JING*, L.-H.; Eur. J. Org. Chem. 2013, 3, 456-459, http://dx.
The present first Michael addition provides an easy and convenient approach to C‐3 alkyl‐substituted indole derivatives with high enantioselectivities whereas diastereoselectivity depends on the cyano substrate.
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