Zum Mechanismus der Photochemie des Benzfurazans
Zum Mechanismus der Photochemie des Benzfurazans
复制标题
苯并呋喃光化学的机理
DOI：
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发表时间：
1976
期刊：
影响因子：
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通讯作者：
Paul Gilgen
中科院分区：
文献类型：
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作者：
W. Heinzelmann;Paul Gilgen
苯呋喃赞光化学反应机理研究。
Mechanistic studies on the photochemical reactions of benzfurazan.
From other works it is known that irradiation of benzfurazan (1) in methanol gives the carbaminacid-ester 4, whereas in benzene the azepinederivative 3 is obtained (Scheme 1). The compounds 5–8 (Scheme 2) have been proposed as intermediates.
In our investigations we detected and characterized by means of UV.- and IR.-spectroscopy the two species 5 and 8. Irradiation of 1 with 350 nm light at room temperature in a strongly polar solvent (e.g. H2O) yields exclusively 5 (Fig. 1) with a quantum yield of 0.48. In non polar solvents (e.g. hexane) 5 isomerizes in a second photochemical step to 8 (quantum yield 0.43) (Fig. 3). Thermally, 5 can be converted back to 1. The rate constant for this reaction at room temperature is 2 · 10–5s–1.
The transformation 5 8 was also investigated at low temperature. There was no direct evidence for any intermediates of the type oxazirene (6) or nitrene (7). However, the formation of azepine 3 upon irradiation of 5 in benzene suggests as intermediate the nitrene 7 which could be converted into 8 in a fast thermal reaction (Scheme 3).