Rhodium-Catalyzed Diastereoselective C–H Activation/[4 + 2] Annulation of α,β-Unsaturated Amides with Bicyclic Alkenes

Abstract

Herein, we report a rare example of rhodium-catalyzed C−H activation/[4 + 2] annulation of alkenyl amides with bicyclic alkenes under mild and green conditions. The reactivity of the rhodium catalyst in this study differed from that observed in cobalt-catalyzed C− H activation/[3 + 2] annulation between vinylic amides and bicyclic alkenes. In addition, the reaction was performed in EtOH at room temperature, which also displayed excellent diastereoselectivity, good functional group tolerance, and air compatibility. A series of novel bridged-ring skeletons were obtained in good to excellent yields. Scale-up experiments were carried out with 1 or 0.75 mol % rhodium catalyst, affording the desired bridged-ring skeleton in excellent yields.

Accessing 7,8-Dihydroquinoline-2,5-diones via Rh-Catalyzed Olefinic C–H Activation/[4+2] Cyclization

“…We hypothesized whether iodonium ylides derived from cyclohexane-1,3-diones could serve as coupling partners in C–H activation reactions to access 7,8-dihydroquinoline-2,5-diones. With our interests in building novel drug-like heterocyclic scaffolds, we present an efficient and mild method for synthesizing 7,8-dihydroquinoline-2,5-diones and analogues through a rhodium-catalyzed C–H activation/[4+2] cyclization reaction between α,β-unsaturated amides and iodonium ylides (Scheme b). The merits of this methodology encompass broad substrate scope, good functional group tolerance, good to excellent yields, environmentally friendly solvent, water and air compatibility, scale-up synthesis with low catalyst loading (0.25–1.5 mol %), and mild reaction conditions.…”