Magnetic‐based picolinaldehyde–melamine copper complex for the one‐pot synthesis of hexahydroquinolines via Hantzsch four‐component reactions

Abstract

A picolinaldehyde–melamine copper complex was loaded on a magnetic Fe3O4 core, so that it contained 0.33 mmol of Cu per gram, and was used as an efficient catalyst. The as‐synthesized catalyst was characterized using various techniques, including Fourier transform infrared spectroscopy, X‐ray diffraction, energy‐dispersive X‐ray spectroscopy, field emission scanning electron microscopy, transmission electron microscopy, vibrating sample magnetometry and thermogravimetric analysis. The catalyst was used to activate the raw materials in the synthesis of hexahydroquinoline derivatives in one‐pot four‐component reactions. Low reaction time (minutes versus half an hour), solvent‐free condition and magnetically separable catalyst are some salient features of the developed catalyst. Also, the optimum amount of catalyst and temperature were determined as 0.07 g and 87.6 °C, respectively, which were obtained using response surface methodology and optimization techniques.

A novel Hercynite‐supported tetradentate Schiff base complex of manganese catalyzed one‐pot annulation reactions

“…In addition, PXRD and FE-SEM analyses of the spent [Hercynite@SiO 2 -Schiff base-Mn(II)] catalyst were compared with the fresh one, indicating that no noticeable crystalline and morphological change is observed instead of surface roughening, slight accumulation, and agglomeration of Hercynite nanoparticles, respectively (Figures 9 and 10), and thus providing strong evidence for excellent durability and stability of the catalyst. [45] 2 15 97 251-253 251-253 [45] 3 15 97 280-283 282-284 [45] 4 12 96 249-250 250-252 [45] (Continues) [45] 6 25 91 248-250 247-248 [69] 7 10 96 233-234 231-233 [45] 8 30 91 238-240 239-241 [45] 9 10 95 279-281 281-283 [45] T [45] 12 20 93 206-263 259-261 [45] 13 30 98 201-203 200-203 [70] (Continues) [70] 16 30 97 257-260 257-259 [70] 17 75 91 199-201 200-201 [70] T [70] 19 75 92 197-199 198-200 [70] 20 95 92 225-228 225-227 [70] 21 30 94 249-252 248-250 [70] (Continues) [70] 23 40 94 218-220 218-220 [71] 24 55 94 234-237 234-236 [70] 25 115 82 305-307 305-307 [72] a Conditions: arylaldehyde (1 mmol), malononitrile (1 mmol), and 2-hydroxy-1,4-naphthoquinone or dimedone (1 mmol), [Hercynite@SiO 2 -Schiff base-Mn (II)] (35 mg), and EtOH (3 ml) under reflux conditions. b Isolated yield.…”

Synthesis of 1‐aminoalkyl‐2‐naphthols derivatives using an engineered copper‐based nanomagnetic catalyst (Fe3O4@CQD@Si (OEt)(CH2)3NH@CC@N3@phenylacetylene@Cu)

“…However, accentuations and small frequency shifts are observed in the cyan IR spectrum; Cu-N peaks at 592 and 693 cm À1 confirm the dative bond formation between copper and nitrogen atoms. [33,47,50]…”

“…[24,25] MNPs have a high affinity to agglomeration, and therefore, suitable protective materials have been investigated for their stabilization. [26][27][28][29][30][31][32][33][34] Surfactant/polymer, silica, and carboncoating or embedding them in a matrix/support are some of the critical approaches adopted to stabilize nanostructured particles. [35,36] It is noteworthy to note that the outer protective shells created as a result of the coating not only stabilize nanoparticles but also provide interaction sites with other synthetic atoms, nanoparticles, and organic groups suitable for their intended applications.…”