Tandem oxidative amidation of benzylic alcohols by copper(II) supported on metformin-graphitic carbon nitride nanosheets as an efficient catalyst

In this research, an efficient heterogeneous catalyst based on graphitic carbon nitride nanosheets (CN) has been reported. The CN was functionalized by 1,3-dibromopropane as a linker (CN–Pr–Br) and subsequently modified with metformin (CN–Pr–Met). Furthermore, the copper(II) was coordinated on modified CN (CN–Pr–Met–Cu(II)) and during this process, 7.94% copper(II) was loaded into the catalyst structure. The synthesized catalyst was evaluated by various techniques including fourier-transform infrared spectroscopy (FT-IR), energy dispersive X-ray spectroscopy (EDS), field emission scanning electron microscopy (FE-SEM), thermogravimetric analysis (TGA), X-ray diffraction (XRD), and inductively coupled plasma atomic emission spectroscopy (ICP-OES). CN–Pr–Met–Cu(II) was used as a catalyst in the synthesis of amides via the oxidation of benzyl alcohols. The conditions of this reaction were optimized in terms of temperature, time, amount of catalyst, type of base, oxidant, and solvent. Moreover, a variety of amides with an efficiency of 75–95% were synthesized. The reaction was carried out in the presence of benzyl alcohols, amine hydrochloride salts, tert-butyl hydroperoxide (TBHP), CaCO₃, and CN–Pr–Met–Cu(II) at 80 °C of acetonitrile solvent. The synthesized catalyst can be easily separated from the reaction medium and reused for 7 consecutive runs without a significant reduction in reaction efficiency.

Structural features influencing the activity of bis-biguanide ligands in the Suzuki–Miyaura cross-coupling reaction in neat water

Catalytic reactions play an integral role in the development of green chemistry. Herein, we report new bis-biguanide compounds containing alkyl and aryl spacers as ligands for the Suzuki–Miyaura cross-coupling reaction in water. These ligands show similar catalytic activity to metformin independently of the nature of the spacer between the two biguanide units.

The chemistry of biguanides: from synthetic routes to applications in organic chemistry

In this minireview, we discuss the chemistry of biguanides and their applications in catalysis. We present their super basicity as a consequence of their structure, the most efficient ways to synthesize symmetric and unsymmetric functionalized biguanides, and their applications in organic catalysis as triazine precursors and ligands in organometallic catalysis.

Biological and catalytic potential of sustainable low and high valent metal-Schiff base sulfonate salicylidene pincer complexes

ONO-Pincer Schiff base salicylidene (HSaln ligand) complexes with VO2+, UO2 2+, MoO2 2+ and Mn2+ ions (MSaln complexes = VOSaln, UO2Saln, MoO2Saln and MnSaln, respectively) were synthesized and fully characterized by different physico-chemical tools. The VOSaln complex was further treated with 1,10-phenanthroline which afforded a new VO-complex (VOSaln-Ph). All complexes and their ligands, as eco-friendly reagents, were explored for their biological potential as antibacterial and antifungal agents. Reactivity of MSaln complexes against the tested pathogen strains exhibited a remarkable inhibitory effect compared to the coordinated ligand (HSaln) and applicable standard drugs. Moreover, the MSaln complex-DNA interaction was investigated by ultraviolet-visible spectroscopy, viscosity and gel electrophoresis techniques affording binding strengths in the order: UO2Saln > MnSaln > MoO2Saln > VOSaln-Ph > VOSaln. Additionally, the biological potential of the investigated compounds was further explored by molecular docking to illustrate the nature of the drug-DNA interactions. All MSaln complexes show respectable anti-proliferative potential as anticancer agents against selected human carcinoma cell lines. Aside from the biological activities these complexes (MSaln complexes) were also investigated for catalytic efficiency in the Suzuki-Miyaura cross-coupling system of phenylboronic acid with 2-bromopyridine in water, sustainably. The results indicated that the MnSaln catalyst performed well with high yield. The catalytic potential of MnSaln was compared in water, water-ionic liquid mixtures and ionic liquids.

Synthesis and Characterization of Biguanide and Biguanidium Surfactants for Efficient and Recyclable Application in the Suzuki-Miyaura Reaction

We report here the synthesis and thorough characterization of a new family of alkylbiguanides and alkylbiguanidium chlorides by ¹H and ¹³C NMR and X-ray diffraction. Their critical micelle concentration was first determined by surface tension measurements. Hexylbiguanide was then studied as a surfactant in the micellar Suzuki-Miyaura cross-coupling reaction. The unexpected low reactivity of the system at high Pd/hexylbiguanide ratios was due to the change of the size and the shape of the aggregates, observed by transmission electron microscopy. The best catalytic activity was obtained for a 1:1 Pd/hexylbiguanide ratio for which the micellar conditions were conserved. Better results were obtained for several substrates, when compared to those previously obtained with metformin under the same reaction conditions. Higher yields and a better recyclability were obtained under micellar conditions with hexylbiguanide.