Synthesis of 4-Hydroxyindolin-2-ones via Phosphoric Acid-Mediated Annulation of β-Nitrostyrenes with 1,3-Cyclohexanedione.

The efficient synthesis of 4-hydroxy-3-arylindolin-2-ones via phosphoric acid-mediated annulation of various β-nitrostyrenes and 1,3-cyclohexanedione is described. This annulation reaction gives a practical method for affording a diverse set of oxindoles, having simple experimentation, readily available starting materials, and very good yields. Additionally, substituted 1,3-cyclohexanediones under the same conditions afforded tetrahydrobenzofuran oxime compounds.

Diversity-Oriented Synthesis of Spiro[chromeno[2,3-]pyridine-3,4'-pyrazole] Derivatives via Pseudo-Three-Component Reactions.

A novel one-pot pseudo-three-component reaction of 2-amino-4-chromen-4-ones with 4-benzylidene-5-alkyl-2-aryl-2,4-dihydro-3-pyrazol-3-ones was investigated for the synthesis of the spiro[chromeno[2,3-]pyridine-3,4'-pyrazole] derivatives. This procedure involved Michael addition, elimination, and hetero-Diels-Alder sequences, affording a series of spiropyrazolone-chromeno[2,3-]pyridines in good yields that possessed relationships between two aryl groups and the carbonyl of the pyrazolone unit.

Synthesis of Fully Substituted Pyrazoles with a Dicyanomethyl Group via DBU/Lewis Acid-Mediated Annulation of D-A Cyclopropanes with Arylhydrazines.

The efficient synthesis of fully substituted pyrazoles with a dicyanomethyl group was developed via an annulation reaction of 2-aroyl D-A cyclopropanes with arylhydrazines in the presence of DBU/AlCl reaction systems. This synthetic approach featured a wide range of readily available aroyl-substituted D-A cyclopropanes with diverse functional groups and a diversity of substituents on pyrazole products and had operationally simple and mild reaction conditions.