A new isatin N,N'-cyclic azomethine imine 1,3-dipole was devised, and an unusual Michael addition with β-nitrostyrene catalyzed by tributylamine under mild conditions has been developed. The new reaction featured the C3 umpolung of oxindole and an unusual formation of double bond. Notably, this new synthon performed as a donor rather than an acceptor. This protocol provided a promising method for the preparation of various 3-aminooxindoles with good yields in moderate diastereoselectivities.
An abnormal [3 + 2]-cycloaddition
and highly effective and convenient
one-step preparation of tetracyclic bispirooxindoles containing two
all-carbon quaternary spirocenters from isatin N,N′-cyclic azomethine imine 1,3-dipole and 3-methyleneoxindole
in the presence of catalytic organic base has been disclosed. A variety
of bispirooxindoles bearing a dinitrogen heterocycle with four adjacent
cycles have been obtained in excellent yields (up to 95%) and diastereoselectivities
(>99:1) under mild conditions.
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