Synthesis, characterization and biological screening of different carbamates derived from 7-hydroxy-4-methyl-2H-1-benzopyran-2-one

A facile and environmentally benign series of carbamates derived from coumarin were synthesized. The synthesis of 7-hydroxy-4-methyl-2H-1-benzopyran-2-one (3) was carried out by gearing up resorcinol (1) and ethyl acetoacetate (2) in a strong acidic media. Carbamates 7 and 8 were synthesized by reacting phenylchloroformate (4) with substituted aliphatic amines 5 and 6 under dynamic pH control in aqueous media in the presence of Na₂CO₃ solution. The molecules 3, 7, and 8 were brominated to 3a, 7a and 8a. The molecules 9, 9a, 10, and 11 were synthesized by further reaction of 3 and 3a with the electrophilic carbamates 7, 7a, and 8 in a polar aprotic solvent using LiH as an activator. Finally, the compound 12 was synthesized by the nitration of 10. Structures of all the compounds were determined by IR, ¹H-NMR, ¹³C-NMR and EI-MS spectroscopic techniques. The bioactivity results of all the synthesized compounds against four gramnegative and two gram-positive bacteria showed that the synthesized coumarin derivatives exhibited moderate to good %age inhibition activity.