ISSN:
0018-019X
Keywords:
Chemistry
;
Organic Chemistry
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Notes:
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).
Additional Material:
4 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/hlca.19760590812
