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

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 intermediate was obtained to indicate a Rh/Rh 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.

Efficient Synthesis of Multiply Seven-Membered-Ring Fused Porphyrins by Rhodium-Catalyzed [5+2] Annulation.

Rhodium-catalyzed reaction of meso-pyrrol-2-yl Ni porphyrins with internal alkynes proceeded smoothly to give singly, doubly, and quadruply seven-membered-ring fused Ni porphyrins as the first example of [5+2] annulation reaction for porphyrin substrates, where the meso-appended pyrrole unit serves as a directing group. These reactions are operationally quite simple and easy. A plausible reaction mechanism was proposed on the basis of the isolation of a key intermediate.