Nucleophilic [3+3]-addition of N-unsubstituted enamine to monocyclic 1H-pyrrole-2,3-diones

A reaction is described of substituted 1H-pyrrole-2,3diones (methyl 1-aryl-3-aroyl-4,5-dioxo-4,5-dihydro-1Hpyrrole-2-carboxylates) with N-alkyland N-arylsubstituted 3-amino-5,5-dimethyl-2-cyclohexen-1-ones providing 1-alkyland 1-aryl-susbtituted 6,6-dimethyl2,4-dioxo-2,3,4,5,6,7-hexahydro-1H-indole-3-spiro2'-(1'-aryl-3'-aroyl-4'-hydroxy-5'-oxo-2',5'-dihydro1'H-pyrroles) [1, 2]. The reaction proceeds as successive attacks of β-CH and NH groups of the enamino fragment of the carbocyclic enamines first on the carbon atom in the position 2 and then on the carbonyl group of the methoxycarbonyl moiety (substituent in the position 2) of pyrrolediones followed by methanol elimination. In reaction of methyl 1-aryl-3-benzoyl-4,5-dioxo-4,5dihydro-1H-pyrrole-2-carboxylates Ia and Ib with N-unsubstituted 3-amino-5,5-dimethyl-2-cyclohexen-1-one (II) taken in a ratio 1:1 performed by boiling in anhydrous benzene for 1–2 min (to the disappearance of the bright red color of initial compounds Ia and Ib) we unexpectedly obtained methyl 11-aryl-12-benzoyl-9-hydroxy-5,5dimethyl-3,10-dioxo-8,11-diazatricyclo[7.2.1.02,7]dodec2(7)-ene-1-carboxylates IIIa and IIIb. Spectral characteristics of compounds IIIa and IIIb are close to those of a model substituted 3,10,13-triazapentacyclo[10.7.1.01,10.04,9.014,19]eicosa-4,6,8,14(19)-tetraene, whose structure was confirmed by XRD analysis [3]. Evidently the bridged compounds IIIa and IIIb formed by the addition of β-CH and NH2 groups of the enamino fragment of carbocyclic enamine II to atoms C2 and C4 respectively of monocyclic pyrrolediones Ia and Ib.