A Facile One Pot Synthesis of New Tricyclic Coumarins from Single Synthon [1

Abstract

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.