Condensed Heterotricycles. Synthesis and Reactions of b ‐Fused 1(2 H )‐Isoquinolinones with unusual enaminic properties

Homophthalic acid ( 1 ) undergoes reaction with 1,2‐, 1,3‐, and 1,4‐diamines to give condensed 1(2 H )‐isoquinolinones like 2 , 4 , 13 , and 25 , which exhibit marked enamine character. These are attacked by electrophiles at the N or C terminus. Some notable reactions of imidazoisoquinolone 2 are those with maleic and acrylic acids to form the tetracycles 48 and 51 , respectively. With propiolic acid, 5 underwent an interesting reaction to form the benzimidazonaphthyridine 53 . An equally interesting behaviour was elicited from 2 in its reaction with formaldehyde, when in addition to the expected methylene‐bridged molecule 59 , the novel spiro derivative 60 was formed by the dimerisation of a presumed azadiene intermediate 63 .