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

Abstract

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 1H NMR, 13C NMR, mass spectra, and elemental analysis.

4-Amino-3-formylcoumarin as Building Block for Construction of Novel Heteroannulated Coumarins: Synthesis, Characterization and Antimicrobial Evaluation

“…4-Amino-3-formylcoumarin (1) was prepared according to the published method. 29 Biological method. The test for the antimicrobial activity was performed on medium potato dextrose agar (PDA) which contained infusion of 200 g potatoes, 6 g dextrose and 15 g agar.…”

Synthesis, Characterization and Antimicrobial and Anticancer Evaluations of Some Novel Heteroannulated Difuro[3,2-c:3′,2′-g]Chromenes

“…A wide range of furo[3,2-g]chromenes and benzofurans have been synthesized using khellin containing electron-withdrawing substituents at position 6 [18,19]. Compounds bearing neighboring amino and carbonyl functions widely serve as good precursors to react with active methylene ketones through Friedländer reactions [20][21][22]. In our previous works, reaction of 4,9-dimethoxy-5-oxo-5H-furo[3,2-g]chromene-6-carboxaldehyde (1) with hydroxylamine hydrochloride in aqueous ethanol yielded carbonitrile derivative 2 which, upon treatment with chloroacetone, yielded the target precursor 3, as shown in Figure 1 [23,24].…”

Facile access to 2‐amino‐4‐aryl‐5H‐chromeno[4,3‐b]pyridine‐3‐carbonitriles through a strategy of one‐pot Michael/cyclization reaction

“…Similarly, the already existing chroman-4-ones [25,26], or their intermediates formed in the reaction process [27], can be used for the preparation of chromeno [4,3-b]pyridine skeleton. In addition to these methods, there are many other methods for constructing these polyheterocycles, such as cycloisomerization [28], Friedlander condensation [29], and cyclization [30,31]. Despite all this progress, it is still urgent to explore easy access to more diverse chromeno [4,3-b]pyridine derivatives.…”