Atomically Precise [Cu-Cu₅₄] Nanocluster-Catalyzed Three-Component Borylative Coupling of Alkynes with Alkyl Bromides...

The well-defined metal nanoclusters (NCs) have emerged as versatile and sustainable catalysts for organic synthesis. However, development of catalyst for simultaneous C─C and C─B bond-forming reactions based on NCs is still unknown. Herein, we developed an atomically precise, mixed-valence (Cu^I/Cu^II), high-nuclearity binary NC, Cu₅₅S₂₀(S^tBu)₂₀(O₃S^tBu)₁₂ [Cu-Cu₅₄], synthesized in high yield via a reducing agent-assisted trithiocarbamate dissociation approach. The [Cu-Cu₅₄] NC was characterized by single-crystal X-ray diffraction (SCXRD), X-ray photoelectron spectroscopy (XPS), electron paramagnetic resonance (EPR), and nuclear magnetic resonance (NMR) spectroscopy. SCXRD uncovers a nested concentric layers architecture with a core {Cu@Cu₁₂@S₁₂@S₈} and a shell {Cu₂₄@Cu₁₂@Cu₆@(S^tBu)₂₀(O₃S^tBu)_{1 2}}, featuring a metal-centered icosahedral Cu@Cu₁₂ unit that has never been observed in copper sulfide [Cu-S] NCs. Distinctly, [Cu-Cu₅₄] NC serve as an efficient catalyst for the highly selective three-component difunctionalization of alkynes with bis(pinacolato)diborane (B₂pin₂) and alkyl electrophiles including alkyl chlorides under mild reaction conditions. The desired trisubstituted vinylboronate esters were obtained in excellent yields with a wide range of electronically diverse carbon electrophiles and alkyne. Additionally, in the absence of electrophiles, the hydroboration of alkynes efficiently afforded vinylboronate esters in high yields with excellent regioselectivity. The synthetic transformations and gram-scale reaction further highlight the usefulness of this protocol.