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.
对2-
甲基吡啶N-
酰亚胺(12b-d和17a-c)进行辐射后,与
噻吩、
呋喃或
吡咯环在
吡啶环的b侧缩合,得到了相应的融合1H-1, 2-二氮杂环(13b-d和18a-c)和3H-1, 3-二氮杂环(14b-d和19a-c),以及母体融合
吡啶(10和15a-c);而N-未取代的N-
亚胺(12a)只生成了1H-1, 2-二氮杂环(13a),没有生成1, 3-二氮杂环。在这个环扩展反应中,初始的光诱导重排可能发生在
吡啶氮的任一侧,从而生成两种二氮杂中间体(21)和(22);前者可能直接生成1, 2-二氮杂环,而后者可能进一步重排为氮杂环中间体(23),然后通过环扩展生成1, 3-二氮杂环。因此,得到的新二氮杂环的一些反应也得到了研究。