Two Stages in the Spiro Heterocyclization of 1H-Pyrrole-2,3-dione with a Carbocyclic Enol

Abstract

Methyl 3-benzoyl-1-(4-methylphenyl)-4,5-dioxo-4,5-dihydro-1H-pyrrole-2-carboxylate reacted with a carbocyclic enol, 2-hydroxy-1,4-naphthoquinone, to give 3′-benzoyl-4′-hydroxy-1′-(4-methylphenyl)-2H-spiro[naphtho[2,3-b]furan-3,2′-pyrrole]-2,4,5′,9(1′H)-tetraone. The intermediate product (Michael adduct) in this spiro heterocyclization, methyl 3-benzoyl-4-hydroxy-2-(3-hydroxy-1,4-dioxo-1,4-dihydronaphthalen-2-yl)-1-(4-methylphenyl)- 5-oxo-2,5-dihydro-1H-pyrrole-2-carboxylate, was isolated for the first time.