New synthetic strategy for Friedlander condensation of 4-amino-2-oxo-2H-chromene-3-carbaldehyde by heterogeneous catalysis

Chromenopyridines are an important class of compound because of their diverse biological activities. In the present work, we have developed convenient route for the synthesis of chromeno[4,3-b] pyridine derivatives (3a-e, 5a-e, and 7a-d) by Friedlander condensation of 4-amino-2-oxo-2H-chromene-3-carbaldehyde with various active methylene compounds. We have used mixed metal oxide catalyst such as nanomaterial Zinc titanate. The reaction was carried out for various solvent systems, also we have altered the concentration of the catalyst. The 2-propanol/water solvent system and 5 mol% catalyst concentration are best as far as yield and rate of reaction are concerned. The structures of the synthesized compounds were confirmed by H-1 NMR, C-13 NMR, mass spectra, and elemental analysis.