Struktur und Reaktivität von isoanellierten heterocyclischen Systemen mit 4n;‐π‐ und (4n + 2)‐π‐Elektronen, XVIII. Benzo[c]thiophene mit symmetrischer Struktur: Modifizierte und optimierte Herstellung nach der S‐Oxid‐Route

Structure and Reactivity of Isoannullated Heterocyclic Systems with 4 n ;‐π and (4 n + 2)‐π Electrons, XVIII. – Benzo[ c ]thiophenes with Symmetric Structure: Modified and Optimized Preparation by the S ‐Oxide Route Benzo[ c ]thiophenes ( 15 ) with symmetric structure have been prepared efficiently from 1,3‐dihydrobenzo[ c ]thiophene 2‐oxides ( 9 ) by reaction with aluminium oxide, by O ‐acylation with trifluoroacetic anhydride, or O ‐alkylation with methyl trifluoromethanesulfonate. The aromatization of the S ‐oxides 9 is achieved by O ‐functionalization, subsequent elimination, and consecutive deprotonation.