Abstract
Irradiation of the 2-methylpyridine N-acylimides (12b-d and 17a-c) condensed with a thiophene, furan, or pyrrole ring on the b-side of the pyridine ring gave the corresponding fused 1H-1, 2-(13b-d and 18a-c) and 3H-1, 3-diazepines (14b-d and 19a-c), together with the parent fused pyridines (10 and 15a-c), whereas the N-unsubstituted N-imide (12a) gave only the 1H-1, 2-diazepine (13a) and no 1, 3-diazepine. In this ring-expansion reaction, the initial photo-induced rearrengement may take place on either side of the pyridine nitrogen to give two kinds of diaziridine intermediates (21) and (22) ; the former may give 1, 2-diazepines directly, whereas the latter may further rearrange to the aziridine intermediate (23), followed by ring-expansion to give the 1, 3-diazepines. Some reactions of the new diazepines thus obtained were also examined.
