Figure 2 : Catalyst design for redox-neutral [4+2] imine/alkyne coupling.

From: Merging rhodium-catalysed C–H activation and hydroamination in a highly selective [4+2] imine/alkyne annulation

Figure 2

(a) Observation of three different annulation products with Rh(I) catalysts. (b) Proposed pathways for imine-directed aromatic C–H bond activation and subsequent alkyne coupling. (c) Proposed N-heterocyclization by intramolecular alkene hydroimination and subsequent competition between oxidative and redox-neutral [4+2] annulation product formations. (d) Mechanistically related reports on intramolecular alkene hydroamination and intermolecular alkyne hydroimination.