Potassium Carbonate to Unlock a GaCl3‑Catalyzed C–H Propargylation of Arenes

• Published in: ACS catalysis Vol. 12; no. 1; pp. 305 - 315
• Main Authors: Vayer, Marie, Rodrigues, Sophie, Miaskiewicz, Solène, Gatineau, David, Gimbert, Yves, Gandon, Vincent, Bour, Christophe
• Format: Journal Article
• Language: English
• Published: American Chemical Society 07-01-2022
• Subjects: C−H propargylation; allenes; kinetic study; gallium; DFT computations
• ISSN: 2155-5435; 2155-5435
• DOI: 10.1021/acscatal.1c03014

A gallium-catalyzed C–H propargylation of electron-rich arenes using bromoallenes is described. The development of this reaction was first hampered by a side hydroarylation process catalyzed by adventitious protons, easily generated from the solvent (1,2-dichloroethane). This hidden Brønsted acid catalysis could be bypassed by using K2CO3 as an insoluble base. The unexpected compatibility of this base with the Lewis acid catalyst GaCl3 allowed a strictly gallium-catalyzed process that was thoroughly studied by kinetics, 71Ga NMR experiments, and DFT computations. The GaCl3/K2CO3 system triggers the C–H propargylation of a wide range of arenes and heteroaromatics using a variety of bromoallenes.