1,4‐Cycloaddition reactions. III. Synthesis of furo[3,2‐ c ]pyrido[2,3‐ g ]quinolines, Furo[2,3‐ a ] [4,7]phenanthrolines, Furo[3,2‐ c ]pyrrolo[2,3‐ g ]quinolines, Furo[3,2‐ c ]pyrrolo[3,2‐ g ]quinolines, and Furo[3,2‐ c ]furo[2′,3′:4,5]pyrido[2,3‐ g ]quinolines from 2,3‐dihydro‐5‐methylfuran and schiff bases

The 1,4‐cycloaddition of 2,3‐dihydro‐5‐methylfuran (II) to 1‐acetyl‐1,2,3,4‐te trahydro‐6‐[( p ‐hydroxybenzylidene)amino]quinoline (VIII) in the presence of boron trifluoride gave two pairs of epimers, namely dl ‐10‐acetyl‐2,3,3a,4,5,7,8,9,10,11b‐decahydro‐4‐( p ‐hydroxyphenyl)‐11b‐methylfuro[3,2‐ c ]pyrido[2,3‐ g ]quinoline (IXa and b) and dl ‐8‐acetyl‐2,3,3a,4,5,8,9,10,11,‐11c‐decahydro‐4‐( p ‐hydroxyphenyl)‐11c‐methylfuro[2,3‐ a ][4,7]phenanthroline (Xa and b). dl ‐9‐Acetyl‐3,3a,4,5,7,8,9,10b‐octahydro‐4‐( p ‐hydroxyphenyl)‐10b‐methyl‐2 H ‐furo[3,2‐ c ] pyrrolo‐[2,3‐ g ]quinoline (XIIIa) was the predominant product isolated from the reaction of II with 1‐acetyl‐5‐[ p ‐(hydroxybenzylidene)amino]indoline (XII). When 1‐acetyl‐6‐[( p ‐hydroxybenzylidene)amino]indoline (XVI) was treated with 2,3‐dihydro‐5‐methylfuran (II), two epimers of dl ‐7‐acetyl‐3,3a,4,5,7,8,9,10b‐octahydro‐4‐( p ‐hydroxyphenyl)‐10b‐methyl‐2 H ‐furo[3,2‐ c ]pyrrolo[3,2‐ g ]quinoline (XVIIa and b) were obtained. dl ‐2,3,3a,4,5,6b,8,9,9a,10,11,12b‐Dodecahydro‐4,10‐bis( p ‐methoxyphenyl)‐6b,12b‐dimethylfuro[3,2‐ c ]furo[2′,3′:4,5]pyrido[2,3‐ g ]quinoline (XX) was formed when 2,3‐dihydro‐5‐methylfuran was allowed to react with N,N' ‐bis( p ‐methoxybenzylidene)‐ p ‐phenylcnediamine (XIX). Structure assignments were made from NMR spectra. None of the compounds exhibited appreciable biological activity.