Covalent Adducts from 2-Substituted 5-Arylazotropones and Nucleophiles and their Fate

Abstract

Working in (CD3)2SO/MeOH 98:2, 2-methoxy-5-[(4-methylphenyl)azo]-2,4,6-cyclohepta- trien-1-one (1a) was found to add either MeO-, giving the stablegcw-dimethoxy α-adduct 2a, or EtS-, to give initially to the C-2 α-adduct 4 a; on neutralization, the latter gave ipso (C-2) replacement of OMe by SEt, while the former returned to the starting material, via the neutral α-adduct 3a. In contrast, in the same medium, 2-ethylthio-5-[(4-methylphenyl)azo]-2,4,6-cy- cloheptatrien-1-one (5 a) was found to add EtS- at both C-2 and C-7; on neutralization prod­ucts of both ipso substitution (5 a) and ipso- plus tele-substitution (C-7) (8) were isolated.