The heteroatom helps! The introduction of an endocyclic sulfur atom enables fine‐tuning of the reactivity and stability of thiacycloalkynes for copper‐free click chemistry. The stabilizing effect of the endocyclic sulfur atom allows the use of highly activated seven‐membered rings as reagents for bioorthogonal copper‐free click chemistry.
Dibenzoselenacycloheptynes were prepared in 3 steps from commercially available reagents and trapped in situ with benzyl azide to form the corresponding triazoles. Surprisingly, the dibenzoselenacycloheptynes also abstracted hydrogen atoms from solvents such as THF or toluene, forming dibenzoselenacycloheptene products. These alkenyl compounds arise from a hydrogen transfer reaction from solvent to the unisolable intermediate, and we postulate that the reaction proceeds via a radical mechanism originating from the strained alkynyl bond that has unusually high radical character.
Difluorinated cyclooctynes are important
reagents for labeling
azido-biomolecules through copper-free click chemistry. Here, a safe,
scalable synthesis of a difluorinated cyclooctyne is reported, which
involves a key homologation/ring-expansion reaction. Sequential ring
expansions were also employed to synthesize and study a novel difluorinated
cyclononyne.
Das Heteroatom hilft! Die Einführung eines endocyclischen Schwefelatoms ermöglicht die Feineinstellung der Reaktivität und Stabilität von Thiacycloalkinen für kupferfreie Klick‐Chemie. Der stabilisierende Effekt des endocyclischen Schwefelatoms ermöglicht die Nutzung von hochaktivierten siebengliedrigen Ringen als Reagentien für die bioorthogonale kupferfreie Klick‐Chemie.
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