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

Tetrasubstituted alkenes are one of the most important classes of aggregation-induced emission luminogens with wide applications in analytical chemistry, bioimaging science, luminescent materials and cancer treatment. However, general methods for the assembly of tetrasubstituted alkenes, especially for unsymmetrical species, remain elusive. The established methods typically require prefunctionalized substrates, sensitive organometallic reagents and multiple-step operation. Herein, we report a dual phosphine/rhodium catalysis for the direct synthesis of unsymmetrical tetrasubstituted alkenes from readily available cyclopropenones, aryl halides and water. This reaction was achieved in a highly efficient and chemoselective manner by a synergistic merger of phosphine-mediated hydration with rhodium-catalyzed arylation, furnishing a diverse set of carboxyl acid–based tetrasubstituted alkenes (>80 examples). The resulting carboxylate groups can be employed as universal tags for the downstream synthesis of unsymmetrical tetraarylethenes. A range of the obtained compounds were demonstrated to be solid-state luminogens with obvious aggregation-induced emission properties. The success of late-stage functionalization of bioactive compounds further illustrate the synthetical utility of this protocol in material development and drug discovery.