Novel Heteroannulated Chromeno[2,3-b]pyridines and Related Compounds Using 6-Methylchromone-3-carbonitrile

Abstract

6-Methylchromone-3-carbonitrile (1) was utilized as synthetic intermediate for construction of a diversity of annulated chromones. Heteroannulated chromeno[2,3-b]pyridines 2-8 were synthesized from reaction of carbonitrile 1 with some methylene active nitriles and cyclic active methylene ketones. Reaction of carbonitrile 1 with isomeric cyclohexanediones in 2:1 molar ratio gave three isomeric (bischromeno)phenanthrolines. Applying Vilsmeier-Haack formylation on 8-methyl-1,2-dihydro-4H-chromeno[2,3-b]quinoline-4,6(3H)-dione (11) produced cyclic β-chloroenaldehyde derivative 14 which upon condensation with benzylamine and p-toludine afforded the corresponding Schiff bases. Condensation reactions of β-chloroenaldehyde 14 with hydrazine hydrate and hydroxylamine hydrochloride produced the novel angularchromeno[2,3-b]pyrazolo[3,4-f]quinoline 17 and chromeno[2,3-b]isoxazolo[5,4-f]-quinoline 18, Structures of the new synthesized products were deduced based on their analytical and spectral data.

Synthetic Approaches for Construction of Novel Angular Heterocyclic Systems Containing Chromeno[2,3-b]quinoline

“…The aldehyde function that was seen in the IR spectrum of compound 1 at 1704 cm -1 has vanished, in the IR spectrum of compound 2. 15 The mass spectra of compound 2 proved the postulated structure and demonstrated the parent ion peak at m/z 379, that matches with its exact mass 379.13. The 1 H NMR spectrum appeared three specific singlets at their typical chemical shift (δ 7.92, 8.62 and 8.85 ppm) assignable to H-11, H-4pyridine and H-3pyrazole.…”

“…The reactivity of the aldehyde group towards nucleophilic reagents is better than the chloro function as previously reported. 15 Firstly, the chemical reactivity of cyclic β-chloroenaldehyde 1 was tested towards a variety of 1,2-binucleophilic reagents. So, reacting compound 1 with phenylhydrazine, in DMF containing triethylamine (TEA) under reflux, afforded the novel chromeno [2,3-b]pyrazolo [3,4-f]quinoline (Scheme 1).…”

“…was prepared according to literature method. 15 All other chemicals used are commercially available.…”

“…13 β-Chloroenaldehyde on variable heterocyclic rings represent an electron deficient substrates and widely utilized as building block for creation of some novel heterocyclic rings through reactions with different binucleophilic reagents. 14 In our previous work, 15 1-chloro-9-methyl-11-oxo-3,4-dihydro-11H-chromeno [2,3-b]quinoline-2carboxaldehyde (1) was synthesized and its reactivity was investigated towards some primary amines, as well as hydrazine hydrate and hydroxylamine. The current work aimed to inspect the reactivity of compound 1 with a diversity of 1,2-and 1,3-as well as 1,4-binucleophiles to create a variety of novel angular heterocyclic compounds including chromeno [2,3-b]quinoline moiety and estimate their antimicrobial efficiency.…”

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

“…Consequently, treating compound 1 with 1,3-cyclohexanedione in molar ratio 1:1 led to 3,4-dihydrochromeno [4,3-b]quinoline-1,11(2H)-dione (6) (Scheme 3). 24 Repeating the reaction in molar ratio 2:1 afforded the novel bis [1]chromeno [4,3-b:4`,3`-J] [1,7]phenanthroline-6,16-dione (7) (Scheme 3).…”