A novel synthesis of N-(4-nitrophenyl)-2-oxo-2H-chromene-3-carboxamide, N-(4-bromophenyl)-2-oxo-2Hchromene- 3-carboxamide and methyl-4-morpholino-2-oxo-2H-chromene-3-carboxylate from the reaction of coumarins with aliphatic and aromatic aminoes