Benzyne, a highly reactive strained cyclic intermediate, is instrumental in the synthesis of a variety of complex molecules, such as natural products, materials, and pharmaceuticals. Benzyne generation is commonly approached through the Kobayashi method which relies on a fluoride base and prevents the use of functional groups that are unstable to fluoride, making the development of alternative methods desirable. Furthermore, the current method for photochemical generation, photolysis of N-acetyl-N-methyltriazeno benzoic acid, results in the extrusion of two equivalents of gas and limited substrate scope due to the broad range of functional groups activated by harsh UV light. The purpose of this project is to develop a new method of benzyne generation using o-phenylsulfonyl benzoic acid as a readily synthesized starting material. o-Phenylsulfonyl benzoic acid was successfully synthesized from iodobenzoic acid and sodium benzenesulfinate through a dual photoredox/nickel-catalyzed cross-coupling reaction. NMR analysis confirmed product formation. We are developing a photochemical reaction using visible light, a transition metal, and o-phenylsulfonyl benzoic acid to generate benzyne and subsequently trap with a diene in a Diels–Alder reaction. We will be using various iron (III) species to coordinate to the carboxylic acid and become excited by light to undergo ligand-to-metal charge transfer (LMCT). Experimental conditions, including solvent choice, reagent ratios, and light wavelength, will be varied to optimize the process. This method is expected to be tolerant to a wider range of functional groups and minimize gas production, allowing for broader use in complex molecule synthesis and offering a safer alternative to current methods.
Photochemical Generation of Benzyne
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Student Abstract Submission