A study of the reactions of 2-aryl-4-hydroxy-6H-1,3-thiazin-6-ones with chromone-3-carboxaldehydes

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

“…148 The compound 172 is also formed from 1 and 3-bromo-4-hydroxycoumarin (1:2 molar ratio) in MeOH-pyridine under reflux. 150 Shutov et al 151 have rectified their earlier report 152 …”

“…234 The compound 372 arises by a sequence of intramolecular lactonizationdelactonisation of the initially formed bis(coumarin-3-yl)(chromon-3-yl)methane 172. 149,151 An equimolar mixture of 1, dimedone and β-naphthol in hot AcOH gives the naphthopyran 373; use of Meldrum's acid in place of dimedone in the above reaction produces the naphthopyrone 374 admixed with the pentacyclic compound 375. Proper mechanisms for the formation of 373-375 have been proposed.…”

“…The formation of the furocoumarin 385 and biscoumarin 386 by treating ChrCHO with 4-hydroxycoumarin and cyclohexylisocyanide in ethanol-pyridine under reflux has been rationalized. 240 The compound 386 is also obtained by reacting bis(coumarin-3-yl)(chromon-3-yl) methane 172 149,151 with cyclohexylamine under similar condition. 240 An equimolar mixture of ChrCHO, cyclohexylisocyanide and ninhydrin in a boiling mixture of DCM and MeOH (7:1 by volume) affords the furochromone 387a that on hydrolysis by HCl-MeOH leads to the fused furanone 387b, no dehydration taking place.…”

Synthesis and Chemical Reactivity of 4‐Oxo‐4H‐1‐benzopyran‐3‐carboxaldehyde

“…Substituted 3‐formylchromone 1 condensed readily with 92 in THF at 60°C in the presence of pyridine giving three products 93 , 94 , and 95 in 55–75% combined yield. The yield was dependent on the nature of the substituent on the chromone and reaction medium (Scheme ).…”

Synthesis of 2,5-Disubstituted Derivatives of Pyrano[2,3-d][1,3]thiazines via the Interaction of 2-Substituted 4-Hydroxy-6H-1,3-thiazine-6-ones with Aldehydes

“…Previously , we studied the reaction of 2‐aryl‐4‐hydroxy‐6 H ‐1,3‐thiazin‐6‐ones with chromone‐3‐carboxaldehydes and discovered one of the products to be a pyranothiazine derivative 3 . Enrapt with this fact, we expanded the set of carbonyl compounds and performed a systematic study of the thiazine 4 reaction with aliphatic and aromatic aldehydes.…”