Rhodium-Catalyzed [5 + 2] Annulation of Pyrrole Appended BODIPYs: Access to Azepine-Fused BODIPYs

Abstract

Rhodium-catalyzed C-H/N-H [5 + 2] annulations of 8-(pyrrol-2-yl)-appended boron-complexed dipyrromethenes (BODIPYs) with internal alkynes have been established to afford a series of azepine-fused BODIPYs with good yields and excellent regioselectivity, in which the pyrrol-2-yl unit serves as the directing group as a rare example. A Rh^I intermediate was obtained to indicate a Rh^I/Rh^III catalytic process involved in this reaction. Importantly, the [5 + 2] C-H annulation is demonstrated as a concise strategy to change the optical properties of BODIPY.