Visible-Light-Induced Radical Carbo-Cyclization/gem-Diborylation through Triplet Energy Transfer between a Gold Catalyst and Aryl Iodides

• DOI: 10.1021/jacs.0c03197
• Publication Date: 2020-04-30T18:32:49Z
• Authors: Lumin Zhang; Xiaojia Si; Frank Rominger; A. Stephen K. Hashmi
• Keywords: Benzothiophene; Benzofuran; Bond cleavage; Photoexcitation

Geminal diboronates have attracted significant attention because of their unique structures and reactivity. However, benzofuran-, indole-, benzothiophene-based benzylic gem-diboronates, building blocks for biologically relevant compounds, are unknown. A promising protocol using visible light aryl iodides constructing valuable blocks, including via radical carbo-cyclization/gem-diborylation alkynes with a high functional group tolerance is presented. The utility these gem-diboronates has been demonstrated by 10 g scale conversion, versatile transformations, the synthesis approved drug scaffolds two drugs, even polymer synthesis. mechanistic investigation indicates that merging dinuclear gold catalyst (photoexcitation 315–400 nm UVA light) Na2CO3 directly responsible photosensitization 254 UV blue LED (410–490 nm, λmax = 465 nm) through an energy transfer (EnT) process, followed homolytic cleavage C–I bond in iodide substrates.