Metal‐Free Aryl Cross‐Coupling Directed by Traceless Linkers. Issue 70 (21st November 2019)

• Record Type: Journal Article
• Authors: Haensch, Veit G.; Neuwirth, Toni; Steinmetzer, Johannes; Kloss, Florian; Beckert, Rainer; Gräfe, Stefanie; Kupfer, Stephan; Hertweck, Christian
• Is Part Of: Chemistry. Volume 25:Issue 70(2019)
• Page Start: 16068
• Page End: 16073
• Publication Date: 2019-11-21
• Subjects: biaryls -- cross-coupling -- density functional calculations -- photochemistry -- synthetic methods; Chemistry -- Periodicals; 540
• DOI: 10.1002/chem.201903582
• Languages: English
• ISSNs: 0947-6539

Abstract

Abstract: The metal‐free, highly selective synthesis of biaryls poses a major challenge in organic synthesis. The scope and mechanism of a promising new approach to (hetero)biaryls by the photochemical fusion of aryl substituents tethered to a traceless sulfonamide linker (photosplicing) are reported. Interrogating photosplicing with varying reaction conditions and comparison of diverse synthetic probes (40 examples, including a suite of heterocycles) showed that the reaction has a surprisingly broad scope and involves neither metals nor radicals. Quantum chemical calculations revealed that the C−C bond is formed by an intramolecular photochemical process that involves an excited singlet state and traversal of a five‐membered transition state, and thus consistent ipso – ipso coupling results. These results demonstrate that photosplicing is a unique aryl cross‐coupling method in the excited state that can be applied to synthesize a broad range of biaryls. Abstract : Without a trace : The scope and mechanism of (hetero)biaryl synthesis by photochemical fusion of aryl substituents tethered to a traceless sulfonamide linker (photosplicing) are reported. The reaction has a broad scope and involves neither metals nor radicals. Theoretical calculations revealed that the C−C bond is formed by an intramolecular photochemical process that is initiated by formation of a U‐shaped conformation, involves an excited singlet state and traversal of a five‐membered transition state, and thus consistently results in ipso – ipso coupling.