Efficient and robust superparamagnetic copper ferrite nanoparticle-catalyzed sequential methylation and C–H activation: aldehyde-free propargylamine synthesis

Abstract

We have described a method for oxidative cross-coupling reactions between N-alkyl anilines and terminal alkynes forming N-aryl-N-methylpropargylamines. Superparamagnetic CuFe₂O₄ nanoparticles were employed as efficient and robust catalyst. The optimum conditions involved the use of tert-butyl hydroperoxide (TBHP) as oxidant and methylating reagent in dimethylacetamide (DMA) solvent at 140 °C. The two-step reaction, methylation and C–C cross-coupling, proceeds efficiently and has high selectivity, and good conversions were achieved in short reaction times. Preliminary mechanistic investigation was conducted. The CuFe₂O₄ nanoparticles could be facilely separated from the reaction mixture by magnetic decantation and could be reused several times with only a slight decrease in catalytic activity.