A facile one pot synthesis of new tricyclic coumarins from single synthon [1]

Article abstract of DOI:10.1002/jhet.1032

A high yielding method for the synthesis of new tricyclic coumarins is reported herein using 8-formyl-7-hydroxy-4-methyl coumarin as a single synthon. Different strategies were employed to synthesize tricyclic coumarins fused with isoxazole and pyran at C7-C8 position in the coumarin skeleton. Functional group modifications during the construction of pyrazolyl coumarin has resulted in novel oxidative ipso nitration. The O-tosylate was subjected to conditions of pressure in a sealed tube experiment, since it was not possible to replace the 7-hydroxy group of coumarin by regular methods. All the compounds synthesized during the present investigation were characterized by IR, ¹H-NMR, ¹³C-NMR, ESI-MS, and elemental analysis. The X-ray diffraction data of some of the intermediate hydrazones are also reported herein.