An efficient lanthanide(III)-catalyzed diastereo- and enantioselective Michael addition of 3-substituted benzofuran-2(3H)-ones to 4-oxo-enoates was developed. The desired adducts with contiguous quaternary-tertiary stereocenters were obtained in up to 99% yield with up to >95/5 dr and 98% ee.
The asymmetric synthesis of 2-amino-5-oxo-5,6,7,8-tetrahydro-4H-chromene derivatives was achieved through a tandem Michael addition-cyclization reaction of easily available cyclohexane-1,3-dione and ethyl 2-cyano-3-phenylacrylates. Moderate to good yields (up to 81 %) and high enantio-
A highly efficient chiral N,N'-dioxide-Mg(OTf)2 catalyst system has been developed for the asymmetric 1,3-dipolar cycloaddition between methyleneindolinones and N,N'-cyclic azomethine imines. The desired pyrazolidine products with contiguous quaternary-tertiary stereocenters were obtained in up to 99% yields with up to 99% ee and >19:1 dr under mild reaction conditions.
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