Synthesis of hybrid polycycles containing fused hydroxy benzofuran and 1H-indazoles via a domino cyclization reaction

Abstract

A stoichiometry controlled domino cyclization reaction of hydrazone and p-benzoquinone to an angularly fused 3H-benzofuro[3,2-e]indazole core with an embedded oxygenated dibenzofuran framework under mild reaction conditions is disclosed. The reaction involves palladium catalyzed 5-hydroxy-1H-indazole formation followed by TFA mediated [3+2] annulation between the in situ formed 5-hydroxy-1H-indazole and p-benzoquinone. The developed method is attractive because of the concomitant formation of two heterocyclic rings with consecutive multiple bond forming events that include two C-C, one C-N and one C-O bonds. Spectroscopic and theoretical studies of the blue emissive benzofuroindazole derivatives have also been described. 2019 The Royal Society of Chemistry and the Centre National de la Recherche Scientifique.