A versatile route to 2-alkyl-/aryl-amino-3-formyl- and hetero-annelated-chromones, through a facile nucleophilic substitution at C2 in 2-(N-methylanilino)-3-formylchromones

Chemistry of 2-amino-4-oxo-4H-1-benzopyran-3-carboxaldehydes

“…heating in 70% or conc. sulfuric acid 13,25 or by heating with a secondary amine as sarcosine, piperidine or Et 2 NH in DMF under reflux. …”

“…A primary amine instead of initially condensing with the aldehyde function of 3 and 4 undergoes an aza-Michael addition to their α,β-unsaturated carbonyl moiety with concomitant expulsion of the nucleofugal disubstituted amine; the net result is thus an amine exchange reaction. [22][23][24][25][26][27][28] As for example, in 8-isopropyl-5-methyl-2-(dimethylamino)chromone-3-aldehyde on treatment with tri-or pentamethylenediamine the dimethylamino group is replaced by NH(CH 2 ) n NH 2 (n = 3 or 5). 22,23 Reactions involving equimolar amounts of 19 and n-propanamine in refluxing toluene gives the amino-aldehyde 33 that can react with a second molecule of n-propanamine giving the imine 34.…”

“…25 A similar amine exchange reaction in the aminochromone 3b is presented in Section 9. Many cyclic amines like pyrrolidine, piperidine, morpholine etc.…”

Synthesis of new benzo[h]‐ and benzo[f]chromeno[2,3‐b]‐pyridine‐5‐ones

“…Ethyl 10-methyl-7-oxo-7H-benzo [7,8] [5,6] 3a and 3b were also prepared according to general procedure B via reaction of 1b, 2b with ethyl acetoacetate (yield 60%, 70% respectively). mp, TLC, IR, and 1 H NMR were identical with that obtained by general procedure A.…”

Synthesis and reactions of 8-allylchromone-3-carboxaldehyde

“…12 Also, the 8-allyl derivatives were used as a precursor for the synthesis of the 8-acetic acid derivatives which exhibit anticancer properties. [13][14][15] Heteroannulated chromones showed significant biological activity including pharmacological, 16 anti-inflammatory and antiplatelet activities.…”