Alkynes are a crucial class of materials with application across the wide range of chemical disciplines. The alkynylation of alkyl halides presents an ideal strategy for assembling these materials. Current methods rely on the intrinsic electrophilic nature of alkyl halides to couple with nucleophilic acetylenic systems, but these methods faces limitations in terms of applicability and generality. Herein, we introduce a different approach to alkynylation of alkyl halides that proceeds via radical intermediates and uses alkynyl sulfones as coupling partners. This strategy exploits the ability of amine-ligated boryl radicals to activate alkyl iodides and bromides through halogen-atom transfer (XAT). The resulting radicals then undergo a cascade of α-addition and β-fragmentation with the sulfone reagent, leading to the construction of C(sp3)-C(sp) bonds. The generality of the methodology has been demonstrated by its successful application in the alkynylation of complex and high-value molecules.
Interlocked coordination cages are a class of multi-cavity architectures with applications in selective anion recognition, adaptive sensing, and catalysis. Controlling the partitioning of their cavities through ligand design and appropriate anion templates is critical to their guest binding scope, yet remains a challenge. Here, we present a thermodynamically stable [Pd2L4](BF4)4 cage assembled from a bis-monodentate ligand featuring a non-coordinating bis-pyrazole methane backbone. As a result of its idealized dimensions, NMR, ESI-MS, and X-ray analyses reveal that halides can trigger the interpenetration of this cage into a [X@Pd4L8]7+ dimer (X = Cl- or Br-) where the halide template resides only in the central pocket. The anion-cation pattern of this interlocked host facilitates exceptional binding affinity for the bisulfate anion in its two outer pockets (up to 106 M-1 in MeCN), strongly outcompeting other tetrahedral anions of similar size.
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