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

A crystalline porous metal–organic framework Ni 2 (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. Ni 2 (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. Ni 2 (BDC) 2 (DABCO) exhibited significantly higher catalytic activity in the coupling reaction than that of other Ni-MOFs such as Ni 3 (BTC) 2 and Ni(HBTC)(BPY). Zn 2 (BDC) 2 (DABCO) and Co 2 (BDC) 2 (DABCO) were found to be completely inactive for the transformation, while the reaction using Cu 2 (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.