Synthesis of 1H-benzo[g]indazole derivatives: propargyl-allenyl isomerization and 6π-electrocyclization involving two aromatic π-bonds

An efficient synthesis of 1H-benzo[g]indazoles starting from Morita-Baylis-Hillman (MBH) adducts is disclosed. The synthesis was carried out from MBH bromide via a sequential copper-catalyzed alkynylation, one-pot synthesis of pyrazole, propargyl-allenyl isomerization, and a 6π-electrocyclization involving two aromatic π-bonds and an allenyl π-bond.