Iron Catalysis in Organic Synthesis

The ability of hydrogen-transfer transition-metal catalysts, which enable increasingly rapid access to important structural scaffolds from simple starting materials, has led to a plethora of research efforts on the construction of heterocyclic scaffolds. Transition-metal-catalyzed hydrogen-transfer annulations are environmentally benign and highly atom-economical as they release of water and hydrogen as by-product and utilize renewable feedstock alcohols as starting materials. Recent advances in this field with respect to the annulations of alcohols with various nucleophilic partners, thus leading to the formation of heterocyclic scaffolds, are highlighted herein.

Transition-metal-catalyzed hydrogen-transfer annulations: access to heterocyclic scaffolds.

Iron phthalocyanine as an efficient and versatile catalyst for N-alkylation of heterocyclic amines with alcohols: one-pot synthesis of 2-substituted benzimidazoles, benzothiazoles and benzoxazoles

Several new bisbenzoxazolyl iridium(III) complexes have been synthesized and characterized through X-ray crystallography. These complexes exhibit excellent catalytic activity in C–C and C–N bond formation reactions from the alkylation of amine with amine, amine with alcohol, ketone with alcohol, and alcohol with alcohol through a borrowing hydrogen reaction. Moreover, these iridium(III) complexes are effective catalysts for the alkylation of amine with alcohol and ketone with alcohol under solvent-free conditions. The catalytic activity of these complexes is greatly enhanced by noncoordinating, while the experiments have excluded the possibility of a “silver effect” (bimetallic catalysis or silver-assisted metal catalysis) from the experiments.

Synthesis, Structures of Benzoxazolyl Iridium(III) Complexes, and Applications on C–C and C–N Bond Formation Reactions under Solvent-Free Conditions: Catalytic Activity Enhanced by Noncoordinating Anion without Silver Effect

Herein, we present the base-metal-catalyzed dehydrogenative coupling of primary alcohols and aromatic diamines to selectively form functionalized 2-substituted benzimidazoles, liberating water and hydrogen gas as the sole byproducts. The reaction is catalyzed by pincer complexes of Earth-abundant cobalt under base-free conditions.

Direct Synthesis of Benzimidazoles by Dehydrogenative Coupling of Aromatic Diamines and Alcohols Catalyzed by Cobalt

Iron-catalyzed 2-arylbenzoxazole formation from o-nitrophenols and benzylic alcohols.

The reaction of nitrophenols with benzylic and heterobenzylic alcohols tolerates a wide range of functional groups.

Iron‐Catalyzed 2‐Arylbenzoxazole Formation from o‐Nitrophenols and Benzylic Alcohols.

Polysaccharides have multiple pharmacological activities without toxicity or side effects. In the present study, the structure, antioxidant and lipid-lowering activities of alfalfa (Medicago sativa L.) polysaccharides (APS) were reported. Three alfalfa root polysaccharides (RAPS), RAPS-1, RAPS-2, and RAPS-3 were isolated, purified, and characterized. The structural analyses demonstrated that the homogeneous RAPS had molecular weights of 22.60, 26.95, and 38.25 kDa, respectively. Furthermore, RAPS-1 was composed of rhamnose, arabinose, xylose, glucuronic acid, glucose, and galactose with molar ratios of 10.25%, 12.53%, 6.58%, 4.56%, 15.74%, and 36.30%, RAPS-2 comprised rhamnose, arabinose, xylose, glucose, and galactose in the molar ratios of 24.07%, 14.48%, 1.24%, 15.05%, and 39.37%, while RAPS-3 was composed of rhamnose, arabinose, xylose, glucuronic acid, mannose, glucose, and galactose in the molar ratios of 31.61%, 11.78%, 1.93%, 5.49%, 3.18%, 14.56%, and 24.63%. The SEM analysis suggested that with the increase of the molecular weight of polysaccharides, its structure is more compact and the stability is stronger. In vitro, RAPS showed strong scavenging ability against DPPH and ABTS free radicals. In addition, RAPS had potent antioxidant activity and reduced the accumulation of lipids in oleic acid-induced NAFLD in HepG2 cells, with RAPS-1 being the most effective. Furthermore, RAPS-1 decreased MDA production, improved the activities of SOD and the total antioxidant capacity of cells, demonstrating that RAPS could effectively restrict lipid accumulation in HepG2 cells induced by oleic acid by restoring the antioxidant system. Western blot analysis indicated that the RAPS-1 can activate the Nrf2/HO-1 signaling pathway to relieve oxidative stress induced by oleic acid, thus playing a role in the treatment of NAFLD. 

Juan Liu

Papers

Iron-catalyzed 2-arylbenzoxazole formation from o-nitrophenols and benzylic alcohols.

Iron‐Catalyzed 2‐Arylbenzoxazole Formation from o‐Nitrophenols and Benzylic Alcohols.

Structural characterization of polysaccharides from Medicago sativa L. roots and lipid-lowering activity in oleic acid-induced HepG2 cells

A novel tandem reactor design based on nano-Cu electrocatalysts and microbial biocatalysts for converting CO2 into ethylene and acetate