Regioselective Synthesis of Spiro[Naphthalene-2(1 H ),3′-[3 H ]Pyrazol]-1-Ones Utilizing 1,3-Dipolar Cycloaddition of Nitrilimines

Abstract

1,3-Dipolar cycloaddition reaction of nitrilimines to a variety of 2-arylmethylidene-3,4-dihydro-1-naphthalenones 1a–h afforded the corresponding spiro[naphthalene-2(1H),3′-[3H]pyrazol]-1-ones 3 and not the isomeric spiro[naphthalene-2(1H),4′-[4H]pyrazol]-1-ones 4, in high regioselectivity. The structure of the isolated products was established through different spectroscopic techniques and confirmed via HMBC.