Simultaneous Formation of 8H-Isoquino[2,1-b][2,7]naphthyridin-8-ones and 13H-Pyrido[4′,3′:3,4]pyrrolo[2,1-b][3]benzazepin-13-ones,a Novel Potential Alkaloidal System

Condensation of 3,4-dihydro-6,7-dimethoxyisoquinoline ( 4 ) with 4-methylnicotinoyl chloride ( 12 ) in refluxing pyridine gives 5,6,13,13a-tetrahydro-2,3-dimethoxy-8H-isoquino2,1-b]2,7] naphthyridin-8-one ( 11 ), along with some of its 13,13a-didehydro derivative 7 . A similar reaction of 4 with 4-(chloromethyl)nicotinoyl chloride ( 14 ) affords, in addition to 7 , the isomeric product 10,11-dihydro-7,8-dimethoxy-13H-pyrido4′,3′:3,4]pyrrolo2,1- b]3]benzazepin-13-one ( 3 ). Analogous pairs of products are obtained from 3,4-dihydro-6,7-(methylenedioxy)- and 3,4-dihydro-6,7,8-trimethoxy-isoquinolines ( 15 and 18 , resp.). The structure of 3 was established by extensive NMR data and confirmed by single-crystal X-ray studies. Structure 7 has the ring system of the Alangium alkaloids like alangimarinc ( 1 ), while the isomeric ring system 3 is predicted to be present in nature on biogenetic reasoning.