SYNTHESIS OF 5-ARYLPYRROLO[2,1-A]ISOQUINOLIN-3(2H)-ONES FROM N-PHENETHYLSUCCINIMIDES AND ORGANOLITHIUM REAGENTS

The 5-aryl-8,9-dialkoxypyrrolo[2,1-a]isoquinolin-3(2H)-ones 1 and 2, which can be considered as 3-arylisoquinoline derivatives, can be efficiently prepared by reaction of the N-1,2-bis(3,4-dimethoxyphenyl)ethylsuccinimides 3 with organolithium reagents, the key steps being a carbophilic addition-cyclization via N-acyliminium ions and Parham-type cyclization, respectively. In both cases, no competition with the cyclization to the five membered nitrogen ring is observed, which is consistent with the fact that when reacted with organolithium reagents N-benzylsuccinimides 4 did not cyclize to the corresponding pyrroloisoindolones 5 and 6.