Reaction of phthalic anhydride with ethyl cyanoacetate: a route to the 2H-indeno[2,1 -c]pyridine-1,9-dione, 2H-indeno[2,1-c]pyridine-3,9-dione, 2H-indeno[2,1-c]pyridazine-3,9-dione, and indeno[2,1-c]pyran-1,9-dione systems

Abstract

The Knoevenagel condensation of phthalic anhydride with ethyl Cyanoacetate gives (Z)-ethyl 2-carbamoyl-8-cyano-3-hydroxybenzofulvene-8-carboxylate (2) in good yield. This compound provides a ready entry into the 2H-indeno[2,1-c]pyridine-1,9-dione, 2H-indeno[2,1-c]pyridine-3,9-dione, 2H-indeno[2,1-c]pyridazine-3,9-dione, and indeno[2,1-c]pyran-1,9-dione systems.