Nitrogen heterocycles. Part 10. Rearrangement of N-methylisoindolo[1,2-b][3]benzazepinium to N-methyldibenzo[a,g]quinolizinium (N-methylberbinium) ions, and a convenient new route to some alkaloid analogues of the isoquinoline series

Abstract

3-(3,4-Dimethoxybenzylidene)phthalide gives, by reaction with glycine, a mixture of (E)- and (Z)-3-(3,4-dimethoxybenzylidene)phthalimidin-2-ylacetic acids (1), which upon hydrogenation afford 3-(3,4-dimethoxybenzyl)phthalimidin-2-ylacetic acid (2). This compound is cyclised by polyphosphoric acid to 13,13a-dihydro-10,11-dimethoxyisoindolo[1,2-b][3]benzazepine-5,8(7H)-dione (3). The ethylene acetal of (3)[(4)] gives, on reduction with lithium aluminium hydride followed by treatment with methyl iodide, 7,8,13,13a-tetrahydro-10,11-dimethoxy-6-methyl-8-oxo-5H-isoindolo[1,2-b][3]benzazepinium iodide ethylene acetal (6). This compound, by the action of alkali, is converted into a mixture of (Z)-5,6-dihydro-10,11-dimethoxy-6-methyldibenz[c,g]-azecin-8(7H)-one ethylene acetal (7), and 5,6,13,13a-tetrahydro-2,3-dimethoxy-7-methyl-5-oxo-8H-dibenzo-[a,g]quinolizinium iodide ethylene acetal (9). When either (6) or (9) are refluxed with sodium deuterioxide in deuterium oxide the methiodide (9)(formed or recovered) appears to be deuteriated at positions 6, 8, 13, and 13a. The methiodide (9) gives, by Hofmann elimination, (E)-5,6-dihydro-10,11-dimethoxy-6-methyldibenz[c,g]-azecin-8(7H)-one ethylene acetal (11), which may be transformed into 5,6,13,13a-tetrahydro-13a-hydroxy-2,3-dimethoxy-7-methyl-5-oxo-8H-dibenzo[a,g]quinolizinium chloride (14), and its ethylene acetal (13). The ketones derived from (6) and (9)[(8) and (10)] give, by treatment with alkali, the same relatively stable ylide (15) which rearranges on heating to 6,7,12,13-tetrahydro-6,13-imino-2,3-dimethoxy-14-methyldibenzo[a,e]-cyclononen-5-one (16).