Synthesis and characterization of new chromeno[2,3-b]pyridines via the Friedländer reactions of 8-allyl-2-amino-4-oxo-4H-chromene-3-carboxaldehyde

Acid-Mediated Synthesis of Chromeno[2,3-b]pyridine Derivatives via Condensation of 2-Amino-3-formylchromones and 1-(Methylthio)-2-nitroenamine Derivatives

“…recent years. For example, Kumar et al reported an efficient method for the formation of fused chromeno[2, 3-b]pyridine derivatives under mild conditions via Au(III)-catalyzed aldol reaction (Scheme 1a) [10] ; Abdel-Rahman et al reported the synthesis of benzochromeno[2, 3-b]-pyridine derivatives from amino-benzochromone-carbaldehydes and ethyl cyanoacetate in 2006 (Scheme 1b) [11] ; Ibrahim synthesized chromeno[2, 3b]pyridines via the Friedländer reactions of 8allyl -2amino -4oxo -4Hchromene -3carboxaldehyde with some carbonyl compounds containing a reactive α-methyl or methylene group in 2010 (Scheme 1c) [12] . Although various synthesis methods for certain substrates have been widely covered in literature, more convenient and effective approaches for the synthesis of chromeno[2, 3-b]pyridine derivatives need to…”

[3+3] Annulation Reaction of 2‐Amino‐4H‐chromen‐4‐ones with Cinnamaldehydes or Aromatic Aldehydes and Ethanal in One Pot: Access to 2‐Aryl‐5H‐Chromeno[2,3‐b]pyridin‐5‐ones

“…[7] In 2020, Alizadeh and co-workers developed a Et 3 N-catalyzed three-component reaction of alkylidenemalononitriles, 3-formylchromones and hydroxylamine hydrochloride to yield 2-aryl-5H-chromeno [2,3-b]pyridin-5-ones (Scheme 1, iii). [19] Compared with substituted chromene substrates such as 3-formylchromones, [20] chromone-3-carbonitrile, [21] 2-methylchromone-3-carbonitrile, [22] 2-amino-chromone-3-carbonitrile, [18] or 2-amino-3-formylchromone, [14a,23] the readily available 2-aminochromones [24] as promising building blocks played a crucial role in the synthesis of polycyclic compounds via annulation reactions. [25] Thus, the annulation of 2-aminochromones was an efficient strategy for chromeno [2,3-b]pyridine synthesis.…”

“…[17] Subsequently, a novel synthesis of 2-arylchromeno [2,3-b]pyridines via the Friedländer reactions of 2-amino-4-oxo-4H-chromene-3-carb-oxaldehyde with acetophenone was contributed by the same lab. [18] In 2013, Patel et al also discovered a modified-Friedländer reaction of 2-aminochromone-3-carbonitrile with acetophenone in AcOH and in the presence of a catalytic amount of concentrated H 2 SO 4 solution to synthesize 2-arylchromeno [2,3b]pyridine derivatives used as antimycobacterial and antimicrobial agents. [7] In 2020, Alizadeh and co-workers developed a Et 3 N-catalyzed three-component reaction of alkylidenemalononitriles, 3-formylchromones and hydroxylamine hydrochloride to yield 2-aryl-5H-chromeno [2,3-b]pyridin-5-ones (Scheme 1, iii).…”

DBU-Promoted Cascade Selective Nucleophilic Addition/C–C Bond Cleavage/Hetero-Diels–Alder Reactions of 2-Amino-4H-chromen-4-ones with β-Nitrostyrenes and/or Aryl Aldehydes: Access to 5H-Chromeno[2,3-b]pyridin-5-ones

“…Subsequently, the Friedländer reaction of 8-allyl-2-amino-4-oxo-4 H -chromene-3-carboxaldehydes and active methyl and methylene compounds were reported for the synthesis of 5 H -chromeno­[2,3- b ]­pyridines bearing an allyl group . Simultaneously, the ring opening and recyclization reactions of chromone-3-carbonitrile with 1,3-bis­(silyloxy)-1,3-butadienes, 2-cyano- N -phenylacetamide, 2-cyano- N -benzyl acetamide, or 1,3-benzothiazol-2-ylacetonitrile in the presence of piperidine were investigated for the construction of 5 H -chromeno­[2,3- b ]­pyridines …”

“…20 Subsequently, the Friedlander reaction of 8-allyl-2-amino-4oxo-4H-chromene-3-carboxaldehydes and active methyl and methylene compounds were reported for the synthesis of 5Hchromeno[2, 3-b]pyridines bearing an allyl group. 21 Simultaneously, the ring opening and recyclization reactions of chromone-3-carbonitrile with 1,3-bis(silyloxy)-1,3-butadienes, 22 2-cyano-N-phenylacetamide, 2-cyano-N-benzyl acetamide, or 1,3-benzothiazol-2-ylacetonitrile in the presence of piperidine were investigated for the construction of 5Hchromeno[2,pyridines. 13d , 23 Hu also described an efficient synthesis of similar compounds via a Domino reaction by employing 2-methyl-4-oxo-4H-chromene-3-carbonitrile with 3-(3-(4-nitrophenyl)-3-oxoprop-1-en-1-yl)-4H-chromen-4-one in the presence of DIPA.…”