Simultaneous Formation of 8 H ‐Isoquino[2,1‐ b ][2,7]naphthyridin‐8‐ones and 13 H ‐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‐8 H ‐isoquino[2,1‐ 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‐13 H ‐pyrido[4′,3′:3,4]pyrrolo[2,1‐ 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.