95538-90-2Relevant academic research and scientific papers
Benzopyrans: Part XVIII-Condensation Reactions of 4,5-Dihydro-4--2-phenyloxazol-5-ones with Nitrogen Nucleophiles
Ghosh, Chandra Kanta,Bandyopadhyay, Chandrakanta
, p. 1048 - 1053 (2007/10/02)
Though the title oxazolones (1a-c; R=H, Me and Cl) have more than one electron deficient centres, the nitrogen nucleophiles NHR2R3 bring about transamidation at their lactone function to give the amides (2) which undergo further transformation depending on the reaction conditions and the nature of R2 and R3 groups.Thus, the acrylamides (2; R2=R3=Et, R2R3= -5-, -2O2-), obtained from 1 and aliphatic secondary amines such as diethylamine, piperidine and morpholine, on refluxing in ethylene glycol afford the pyrrole-2-carboxamides (10).With diethylaminein refluxing methanol, the oxazolone 1a, however, undergoes alkoxide induced transformation to methyl pyrrole-2-carboxylate (11; R1 = H).In refluxing acetic acid, the anilide (2; R2=H, R3=Ar) undergoes cyclodehydration to the imidazolone (7), the hydrazide (2; R2 = H, R3 = NMe2) isomerises to the pyridone (8) and the hydrazide (2; R2=H, R3=NHPh) cyclises to the triazine (9).The oxazolones (1a-c) when refluxed with an equimolar or catalytic amount of an aromatic secondary or tertiary amine in ethanol produce the corresponding 2H,5H-pyranobenzopyrans (6a-c), the acrylic ester (2; OEt in place of NR2R3) sometimes contaminating the former (6).
