Di-π-Methan-Umlagerungen einfacher Allylbenzolderivate mit π-Donorsubstituenten

Abstract

The photochemistry of the three isomeric (1'-methylallyl)anisoles 3, of 2-(1',1'-dimethylallyl)anisole (7) as well as of 2-(2'-butenyl)-N,N-dimethylaniline (15) and 2-(3'-methyl-2'-butenyl)-N,N,4-trimethylaniline (17) under direct irradiation in methanol is investigated (see scheme 2, 3, 5 and 6). In all cases di-π-methane rearrangements of the reactants in the triplet state are observed. But the products from the reaction of o- and p-3, 7 and 17 are accompanied by compounds arising from consecutive photo-reactions of the primarily formed cyclopropane derivatives. Side-reactions of the starting materials, i.e. photo-fragmentation and intramolecular [2 + 2]-cycloaddition of the allyl group, respectively, interfere when p-2 (see scheme 3) and 7 (see scheme 3 and 4) are irradiated in methanol. A novel type of photo-Emde degradation seems to concur to the unusual transformation of the di-π-methane rearrangement product of 17 (see scheme 6).