Multicomponent Petasis Reaction for the Synthesis of Functionalized 2-Aminothiophenes and Thienodiazepines

Multicomponent Petasis reaction has been widely applied for the synthesis of functionalized amine building blocks and biologically active compounds. Employing primary aromatic amines that are not typical reactive substrates contributes to expand the application scope of the Petasis reaction. In this study, we demonstrated the synthesis of functionalized 2-aminothiophenes using Gewald-reaction-derived 2-aminothiophenes as the amine substrates, whose low reactivity in the Petasis reaction was overcome using hexafluoro-2-propanol as the solvent in a mild condition. The obtained Petasis products are amenable for further transformations owing to the presence of multiple functional handles. A following intramolecular cyclization of selected Petasis products afforded substituted tricyclic heterocycles that incorporate a pharmaceutically interesting thienodiazepine moiety.