Novel Chromeno[2,3-b]pyridines from Basic Rearrangement of 4-Oxo-chromene-3-carbonitrile

A new series of 2,3-disubstituted-5-oxochromeno[2,3-b]pyridine derivatives has been obtained throughout a 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU)-catalyzed reaction of 4-oxo-4H-chromene-3-carbonitrile with various active methyl and methylene compounds. The Friedlander reaction of 2-amino-4-oxo-4H-chromene-3-carboxaldehyde with the same active methyl and methylene compounds led to the identical products, suggesting that basic catalyzed ring rearrangement took place during the course of reaction.