Photochemisches Verhalten von 1‐ und 2‐alkylierten 1,2‐Dihydronaphtalinen

Abstract

AbstractIrradiation of 1‐alkyl‐substituted 1,2‐dihydronaphthalenes (10, 11, 12) with a lowpressure mercury lamp yields by ring opening ω‐vinyl‐o‐quinodimethanes, which undergo [1, 7] H‐shifts to give 1,2‐divinyl‐benzenes (8, 18, 23; cf. schemes 2, 3 and 4). In a further photoreaction of the divinylbenzenes, benzobicyclo [3.1.0]hex‐2‐enes (17, 19, 22) are formed. 2‐Alkyl‐substituted 1,2‐dihydronaphthalenes (13, 14, 15, 16) are transformed by irradiation into ω‐vinyl‐o‐quinodimethanes, which show [1, 7] H‐shifts to yield in this case 2‐(buta‐1′, 3′‐dienyl)‐toluenes (9, 25, 26, 27; cf. schemes 6 and 7). The irradiation of 1‐methyl‐ (10) and 1‐ethyl‐1, 2‐dihydronaphthalene (11) with a high‐pressure mercury lamp produces, besides the products of irradiation using the lowpressure lamp, 2‐ethyl‐allenylbenzene (24), and (from 11) 4‐exo‐ethyl‐benzobicyclo[3.1.0]hex‐2‐ene (exo‐20) and 2‐propyl‐allenylbenzene (21), respectively (cf. scheme 5). Obviously, these products arise from a photreaction of the primarily formed ω‐vinyl‐o‐quinodimethanes a.