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 crystalline porous metal-organic framework Cu-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), hydrogen temperature-programmed reduction (H-2-TPR), and nitrogen physisorption measurements. The Cu-2(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. (C) 2014 Elsevier Inc. All rights reserved.