Synthesis of some new 4-Heteroaryl substituted 3-cyano coumarins starting from 3-formylchromones

Abstract

A series of new 4-pyrazolyl/benzopyrano[4,3-6]pyridinyl/pyrazolo[l,5a]pyrimidinyl-3-cyanocoumarins (5, 6 & 7) have been synthesized starting from 3formylchromones (1).

Chemistry and application of 4‐oxo‐4H‐1‐benzopyran‐3‐carboxaldehyde

“…Both 2-aminochromone 162 [146] and 4-amino-2H-1-benzopyran [39] behave as enamines to undergo initial Michael addition to the , -unsaturated aldehyde 1 to give ultimately the fused pyridines 164 and 165, respectively. 5-Aminopyrazole 166 (R = alkyl, aryl), however, behaves differently from the aforesaid two aminobenzopyrans; it undergoes through its exocyclic and endocyclic nucleophilic nitrogens a [3+3]cyclization with 1 with concomitant opening of the pyran ring to afford the pyrazolo[1,5-a]pyrimidine 167 [147].…”

“…Condensation of 33 with ethyl cyanoacetate leads to a coumarin derivative 36 [39]. The thiosemicarbazone 34 (X = S, R = H) undergoes cyclisation with BrCH 2 CO 2 Et and ClCH 2 COMe to give the thiazole derivatives 37 (X = OH, keto form), and 37 (X = Me), respectively [40].…”