Convenient Replacement of the Hydroxy by an Amino Group in 4 Hydroxycoumarin and 4-Hydroxy-6-methyl-2-pyrone under Microwave IrradiationAuthor(s): Edmont V. Stoyanov | Ivo C. Ivanov
Journal: Molecules ISSN 1420-3049
Volume: 9; Issue: 8; Start page: 627; Date: 2004;
Keywords: 4-Hydroxycoumarin | 4-aminocoumarins | 4-hydroxy-2-pyrones | 4-amino-2-pyri- dones | microwave irradiation | nucleophilic replacement.
The reaction of 4-hydroxycoumarin (1) with some primary amines 2a-h and morpholine (2i) under microwave irradiation occurred without opening of the lactone ring to give N-substituted 4-aminocoumarins 3a-i in excellent yields. Under the same experimental conditions, 4-hydroxy-6-methyl-2-pyrone (4) reacted with benzylamine (2e) or 2-phenyl- ethylamine (2f) to give the corresponding N,N'-disubstituted 4-amino-6-methyl-2-pyridones 5e,f. The main advantages of this procedure are dramatically shortened reaction times, higher amine utilization and considerably improved yields.