Pyrrolo[1,2-b]isoquinoline-5,10-diones and indolizine-5,8-diones

Abstract

The synthesis of pyrroloisoquinolinediones from phthalic anhydride and pyrrolylmagnesium halides has been improved. A new synthesis, by cyclization of the novel 1-(2-carboxybenzoyl)pyrroles, was generally preferable. From pyrrolylmagnesium bromide and dimethylmaleic anhydride, followed by cyclization, 6,7-dimethylindolizine-5,8-dione was obtained. The process failed with maleic anhydride. Pyrrolo[1,2-b]isoquinoline-5,10-dione could be dinitrated in the pyrrolo ring (with some oxidation to isoquinoline-1,3,4-trione), reduced to 10-hydroxy-3,5-dihydropyrrolo[1,2-b]isoquinolin-5-one by zinc and acetic acid, and hydrogenated over palladium on carbon to 10-hydroxy-1,2,3,5-tetrahydropyrrolo[l,2-b]isoquinolin-5-one. The dihydro derivative reverted in air to the dione.