Propargylamine synthesis via sequential methylation and C–H functionalization of N-methylanilines and terminal alkynes under metal–organic framework Cu2(BDC)2(DABCO) catalysis

• A general methodology for copper-catalyzed propargylamine synthesis via aldehyde-free Mannich-type reaction is reported.
• Cascade methylation by tert-butylperoxide and C–C bond formation of N-methylanilines and terminal alkynes was proposed.
• The catalyst can be facilely recovered and reused.

A crystalline porous metal–organic framework Cu2(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), hydrogen temperature-programmed reduction (H2-TPR), and nitrogen physisorption measurements. The Cu2(BDC)2(DABCO) was used as a heterogeneous catalyst for the direct C–C coupling reaction via cascade methylation and C–H functionalization of N-methylaniline and terminal alkynes. tert-Butyl hydroperoxide also served as the methylating reagent in the transformation, and N-methyl-N-(3-phenylprop-2-ynyl)benzenamine but not N-(3-phenylprop-2-ynyl)benzenamine was produced as the principal product. The Cu-MOF could be recovered and reused several times without a significant degradation in catalytic activity. To the best of our knowledge, the direct oxidative C–C coupling between N-methylaniline and alkynes with methylation transformation was not previously mentioned in the literature.

Figure optionsDownload high-quality image (100 K)Download as PowerPoint slide