Strain-Release-Driven Phosphine and Rhodium Catalysis: Facile Synthesis of Unsymmetrical Tetrasubstituted Alkenes

Tetrasubstituted alkenes are one of the most importantclassesof aggregation-induced emission luminogens with wide applicationsin analytical chemistry, bioimaging science, luminescent materialsand cancer treatment. However, general methods for the assembly oftetrasubstituted alkenes, especially for unsymmetrical species, remainelusive. The established methods typically require prefunctionalizedsubstrates, sensitive organometallic reagents and multiple-step operation.Herein, we report a dual phosphine/rhodium catalysis for the directsynthesis of unsymmetrical tetrasubstituted alkenes from readily availablecyclopropenones, aryl halides and water. This reaction was achievedin a highly efficient and chemoselective manner by a synergistic mergerof phosphine-mediated hydration with rhodium-catalyzed arylation,furnishing a diverse set of carboxyl acid-based tetrasubstitutedalkenes (>80 examples). The resulting carboxylate groups can beemployedas universal tags for the downstream synthesis of unsymmetrical tetraarylethenes.A range of the obtained compounds were demonstrated to be solid-stateluminogens with obvious aggregation-induced emission properties. Thesuccess of late-stage functionalization of bioactive compounds furtherillustrate the synthetical utility of this protocol in material developmentand drug discovery.