A Two-Step Synthesis of Unprotected 3-Aminoindoles via Post Functionalization with Nitrostyrene.

A novel, low-cost method for the preparation of not easily accessible free 3-aminoindoles has been developed. This approach is based on a well-established reaction between indoles and nitrostyrene in the presence of phosphorous acid, which results in the formation of 4'-phenyl-4'H-spiro[indole-3,5'-isoxazoles]. The latter could be transformed to corresponding aminated indoles by reaction with hydrazine hydrate in good or excellent yields upon microwave-assisted heating.

A Convenient Way to Quinoxaline Derivatives through the Reaction of 2-(3-Oxoindolin-2-yl)-2-phenylacetonitriles with Benzene-1,2-diamines.

Microwave-assisted reaction between 2-(3-oxoindolin-2-yl)-2-phenylacetonitriles andbenzene-1,2-diamines leads to the high-yielding formation of the corresponding quinoxalines as sole, easily isolaable products. The featured transformation involves unusual extrusion of phenylacetonitrile molecule and could be performed in a short sequence starting from commonly available indoles and nitroolefins.