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International audience; A green method for the production of cobalt/(TEMPO-Cellulose) aerogel heterogeneous catalyst was developed. The preparation implied the reduction of CoSO4 by NaBH4 in TEMPO-Cellulose water dispersion in ambient conditions. The formation of Cobalt nanoparticles is due to the presence of “TEMPO-Cell” which screens the Co2+ ions and prevents their combination with boron. SEM, XRD, EDX, FTIR, TEM and XPS were used to analyze the structure of the catalyst and showed that metallic cobalt particles have nanometric size and are well dispersed in the aerogel. The catalyst showed excellent activity for model reactions such as the reduction of 4-nitroaniline, 4-nitrophenol and 2-nitrophenol in water, in the presence of NaBH4. The reaction kinetic was studied by UV–visible spectroscopy, which showed that this catalyst is efficient to achieve 100 % reduction with high reaction rate and turnover frequency. The aerogel catalyst was reused more than ten times without significant loss of its catalytic activity.

In this study, a cellulose nanomaterial (Cellulose nanofiber, CNF) was employed as solid support and stabilizing agent for the highly active cobalt nanoparticles via in situ green and facile synthesis as an environmentally benign supported catalyst. The process of preparation involves the reduction of cobalt precursors on the surface of CNF in ambient conditions with the presence of NaBH4. The structure of the synthesized organic-inorganic hybrid Co/CNF was characterized by field emission scanning electron microscopy, energy dispersive spectroscopy and Fourier transform infrared spectroscopy. The hybrid aerogel nanocomposite Co/CNF demonstrated excellent catalytic activity for the reduction of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP) in water with NaBH4. Even with a very low amount of catalyst and was found to be good enough to achieve 100% reduction of 4-NP with a higher reaction rate (in 8 min). The heterogeneous nanocomposite catalyst was easily isolated from the reaction mixture by simple filtration and reused 5 times without significant loss of its catalytic activity.

Natural polymers, especially polysaccharides, are explored for application in heterogeneous catalysis as immobilization support for metallic or organometallic catalysts. In this work, we designed a green Pd(0) based supported catalyst for Heck C-C coupling reactions. The support was produced from Nanofibrillated Cellulose (NFC) extracted from the rachis of date palm tree. The NFC was prepared by mechanical and chemical pretreatment by mean of TEMPO oxidation of the palm tree cellulose pulp. The Pd(0)-supNFC catalyst was characterized by mean of FTIR spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM) and elementary analysis (EDX), and tested on Heck cross-coupling reaction in comparison with Pd(OAc)2 with the same reaction under homogeneous conditions. Notable properties were found: eco-friendly processing, good reaction yields, very short reaction times, easy separation and reusability with insignificant loss of catalytic activity. More precisely the catalytic tests showed that the Pd(0)-supNFC catalyst has an excellent reactivity with a high reaction yield (90%) with low catalyst loading and short time reaction. In addition, the catalyst retained its activity even after three cycles.

A three-component, one-pot, stepwise Sonogashira–­heterocyclization–Heck-coupling process was developed starting from either haloarenecarboxamides, halophenols or haloanilines, terminal alkynes and electron-deficient alkenes. Cyclic imidate-, benzofuran-, or indole-type products are obtained, respectively, in useful yields, being typically better than those obtained with isolation of the intermediate Sonogashira adducts. Very high 6-endo selectivity is maintained with imidate-type coupling products despite the presence of copper salts carried over from the Sonogashira coupling.