Convenient synthesis of 3-unsubstituted oxindole-1-carboxamides

The multiple reactivity of the mesomeric anion formed by N- or C(3)-deprotonation of 3-unsubstituted oxindoles hampers the selective introduction of substituents onto the nitrogen atom. A conveniently applicable reaction sequence has been elaborated for the synthesis of 3-unsubstituted oxindole-1-carboxamides starting from the easily available 1,3-bis(phenoxycarbonyl)oxindoles. Selective amidation of the N-phenoxycarbonyl moiety and subsequent removal of the C(3)-phenoxycarbonyl moiety furnished the title compounds, which are useful building blocks for further functionalization. Besides the novel methodologies, several new representatives of this valuable compound family and their intermediates are also described below.