Aryne Generation from Aryl Halides Via Photothermal Red-Light Activation

Multistep synthetic methods requiring harsh conditions and poor atom economy are central to the generation of aryne precursors. The Kobayashi method remains the standard for aryne generation, and newer methods have relied on similar strategies for activated precursors for mild aryne generation. Here, we show the generation of arynes from commercially available aryl or heteroaryl halides via photothermal conversion in air using red light. With photothermal conversion, a high-energy aryne intermediate is formed via inhomogeneous thermal gradients. Nitrogen nucleophiles then readily trap the aryne intermediate to forge C-N bonds, an essential bond in pharmaceutical and agrochemical synthesis, simplifying traditional methods that use aryl halides as aryne precursors. A wide range of readily available heteroaryl and aryl halides undergo amination in less than 20 min under red light irradiation of carbon black. The product regioselectivity matches the expected distribution from aryne trapping, further supporting an aryne mechanism. Additionally, we show aryne trapping via a [4 + 2] cycloaddition, with a sulfur nucleophile, and a one-pot double amination with 1,2-dibromobenzene. This photothermal method using commercially available aryl/heteroaryl halides enables on-demand access to arynes without inert conditions, solvent, and additional synthetic steps, overcoming operational barriers of existing approaches.