Palladium-Catalyzed Dearomatization of Benzothiophenes: Isolation and Functionalization of a Discrete Dearomatized Intermediate.

A Pd-catalyzed decarboxylative dearomatization reaction of a heterocyclic substrate enables access to an uncommon reaction intermediate that rearomatizes in the presence of amine bases in a net C-H functionalization sequence. The dearomatized benzo[ b ]thiophene intermediate bears an exocyclic alkene that can be functionalized through cycloaddition and halogenation reactions to deliver complex heterocyclic products.