Synthesis of Isoquinolone, 1,2-Benzothiazine, and Naphtho[1′,2′:4,5]imidazo[1,2-a]pyridine Derivatives via Rhodium(III)-Catalyzed (4 + 2) Annulation

In this study, we report a novel and efficient synthetic method to construct isoquinolone scaffold via the Rh(III)-catalyzed (4 + 2) annulation of benzamide with an unreported coupling reagent methyl 2-chloroacrylate. Accordingly, other valuable 1,2-benzothiazine and naphtho[1′,2′:4,5]imidazo[1,2-a]pyridine derivatives are also obtained through a similar synthetic protocol. Thus, our developed method is highlighted by high yield and reaction versatility.