Rhodium(III)-Catalyzed Annulative Coupling of Sulfoxonium Ylides and Allenoates: An Arene C-H Activation/Cyclopropanation Cascade.

Rhodium(III)-catalyzed annulative coupling of sulfoxonium ylides with allenoates was achieved, forming highly functionalized cyclopropanes with a quaternary carbon center by means of the sulfoxonium ylide functionality as a traceless bifunctional directing group and C4 synthon via an arene C-H activation and cyclopropanation cascade. The protocol features simultaneous formation of three new C-C bonds in one pot with excellent diastereoselectivity. The resultant cyclopropanation products could be further transformed to diverse synthetically useful compounds.