Cycloaddition in Condensed Isoindoles. 3. Synthesis of Novel Tricyclic Derivatives of the 7-Azabenzonorbornene System

We have studied the reaction of 6-methyl-5,6-dihydroisoindolo2,1-a]quinazolin-5-one with maleinimide derivatives for a 1:2 reagent ratio. We have shown that the reaction products are tricyclic derivatives of the 7-azabenzonorbornene system, and specifically 11-(2,5-dioxo-1-R-tetrahydro-1H-3-pyrrolyl)-2-methyl-20-R-2,10,20-triazahexacyclo9.6.5.0^1,10.0^4,9.0^12,17.0^18,22]docosa-4(9),5,7,12(17),-13,15-hexaene-3,19,21-triones. We discuss a hypothesis for a probable reaction mechanism.