Nickel-catalyzed oxidative coupling of alkynes and arylboronic acids using the metal–organic framework Ni2(BDC)2(DABCO) as an efficient heterogeneous catalyst

Abstract

A crystalline porous metal–organic framework Ni₂(BDC)₂(DABCO) was synthesized and characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), thermogravimetric analysis (TGA), Fourier transform infrared (FT-IR), atomic absorption spectrophotometry (AAS), and nitrogen physisorption measurements. Ni₂(BDC)₂(DABCO) could be used as an efficient and recyclable heterogeneous catalyst for the cross-coupling reaction between phenylboronic acids and phenylacetylenes in the presence of molecular oxygen in air as the stoichiometric oxidant. High conversions of the cross-coupling products were achieved with no homo-coupling products being detected by GC. Ni₂(BDC)₂(DABCO) exhibited significantly higher catalytic activity in the coupling reaction than that of other Ni-MOFs such as Ni₃(BTC)₂ and Ni(HBTC)(BPY). Zn₂(BDC)₂(DABCO) and Co₂(BDC)₂(DABCO) were found to be completely inactive for the transformation, while the reaction using Cu₂(BDC)₂(DABCO) as the catalyst led to the formation of a 10% homo-coupling product. To the best of our knowledge, a nickel-based catalyst was not previously used for the oxidative coupling reactions between phenylacetylenes and phenylboronic acids.