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 4n;‐π and (4n + 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.