Gold-Catalyzed Ascorbic Acid-Induced Arylative Carbocyclization of Alkynes with Aryldiazonium Tetrafluoroborates

• Published in: ACS catalysis Vol. 11; no. 15; pp. 8968 - 8977
• Main Authors: Medina-Mercado, Ignacio, Colin-Molina, Abraham, Barquera-Lozada, José Enrique, Rodríguez-Molina, Braulio, Porcel, Susana
• Format: Journal Article
• Language: English
• Published: American Chemical Society 06-08-2021
• Subjects: gold; aryldiazonium salts; arylative carbocyclization; ascorbic acid; polymorphism
• ISSN: 2155-5435; 2155-5435
• DOI: 10.1021/acscatal.1c01826

We describe, herein, arylative carbocyclization of alkynes catalyzed by gold. In this process, Au­(I) is oxidized to Au­(III) with aryldiazonium tetrafluoroborates following a photosensitizer-free and irradiation-free protocol. Ascorbic acid acts as a radical initiator, generating aryl radicals. According to DFT calculations, these radicals are added to Au­(I), leading to a Au­(II) species that is further oxidized to Au­(III) with the assistance of a tetrafluoroborate anion. The overall arylative carbocyclization process is very energetically favorable, transforming arylpropargyl ethers into valuable 3,4-diaryl-2H-chromenes in a completely regio- and stereoselective fashion. Furthermore, we show that one of the synthesized 3,4-diaryl-2H-chromenes exhibits polymorphism with marked differences in the color of its crystals, a property that could lead to the development of colored derivatives in the future.