Tetrahedron Green Chem最新文献

This study unveils a novel approach by efficiently loading earth-abundant cobalt onto a covalent organic framework (COF) for catalyzing the hydrogenation of nitroarenes to aryl amines. The synthesized Co@NC650 nanocomposites exhibit enhanced graphitization and catalytic performance, attributed to synergistic interactions between cobalt and the carbon matrix. The Co@NC650 The resulting material is thoroughly characterized using techniques such as PXRD, XPS, FE-SEM, TEM, and FT-IR. Utilizing this synthesized catalyst, a chemoselective reduction of nitroarenes to corresponding amines is demonstrated under relatively mild conditions, employing molecular hydrogen as sole reductant without any additives or bases. The methodology delivers high yields and exhibits tolerance towards wide range of functional groups. The chemoselective hydrogenation is achieved even in the presence of other potentially reducible functional groups such as ketones, carboxylic acids, amides, sulphonamides, and chalcones. Selected examples showcasing the synthesis of biologically important amines are presented. Furthermore, the proposed catalyst demonstrates reusability without any loss of activity.

An eco-friendly, mild and efficient acylation of various nucleophiles with alkenyl carboxylates via inorganic base catalysis is described. Among five inorganic base species examined, K₂CO₃ was proved to be the most efficient catalyst for the acylation. A broad variety of acylated products were achieved within 15 min at room temperature in high yields. In addition, we found that the 3-position of indoles should have a suitable substituent group under this procedure.

Glycols are non-volatile, non-flammable solvents for efficient, facile, and environmentally benign syntheses of various types of symmetric and non-symmetric squaraine dyes, thus providing a viable alternative to conventionally used n-butanol/toluene system.

Ammonia (NH₃) stands as a cornerstone compound across industries, pivotal in agriculture, chemicals, and energy sectors. However, the conventional Haber-Bosch process demands high pressures, temperatures, and fossil fuels, calling for sustainable alternatives. Electrocatalytic Nitrogen Reduction Reactions (E-NRRs) and Photocatalytic Nitrogen Reduction Reactions (Photo-NRRs) present innovative routes, leveraging electricity and direct sunlight to convert nitrogen (N₂) to NH₃ under mild conditions, reducing emissions and softening energy requirements. Catalysts play a strategic role in these approaches, overcoming activation barriers and enhancing efficiency. However, some challenges still need to be addressed. Indeed, noble metals exhibit limits and their scarcity, geopolitical involvement, and often fluctuating costs inhibit large-scale use. Non-noble metals offer promise but require optimization and face durability concerns. Finally, carbon-based catalysts present challenges in optimization and doping. In this scenario, a molecular-based approach, comprising both specific single coordination-based molecules with transition metal centres and either metal centre coordination-based or fully organic multi-dimensional networks originating from direct molecular organic precursors, overcomes these issues while keeping the benefits of the previously mentioned classes of compounds. This mini-review explores the molecular approach to E-NRRs and Photo-NRRs from coordination compounds carrying porphyrins and phthalocyanines as organic ligands to polymeric networks based on coordination compounds between metallic centres and organic ligands (Metal-Organic Frameworks), and to networks of molecular organic units into multi-dimensional structures (Covalent Organic Frameworks). Mechanistic insights into E-NRRs and Photo-NRRs pathways elucidate N₂ conversion to NH₃. A critical comparative evaluation of reported catalysts has been carried out to highlight the limits and the possibilities of each class of compounds. Although challenges persist in terms of stability, cost and complexity of the synthesis, the use of a molecular approach in NRRs represents one of the most promising routes towards the sustainable preparation of ammonia.

A hypervalent iodine-catalyzed phenolic coupling reaction of norbelladine derivatives was examined with a catalytic amount of iodobenzene and meta-chloroperbenzoic acid as the terminal oxidant. The addition of acetic acid dramatically accelerated the reaction rate even at room temperature, and the cyclized products were successfully obtained under mild reaction conditions. The methods were applicable to the racemic total synthesis of oxomaritidine.

Herein we have described the Pd-catalyzed sonochemistry driven by [BMIM]-IL as re-useable solvent to synthesize various carbazole scaffolds from 2,2′-dibromodiphenyl. Diverse primary amines were utilised as coupling partners in the presence of [PAIM][NTf₂], which exhibits an impactful promoter in the IL medium, thereby avoiding the need for hazardous VOC's. The recyclability of ionic liquids highlights the green approach of the reaction. Further, the synthesized carbazole scaffolds were assessed for antimicrobial activity. Compounds 3e and 3g are found to be highly active. The most probable binding sites for these scaffolds were screened through a computer-simulated docking method with targeted protein.

The transformation of biomass derived platform molecules is an interesting approach to produce valuable chemicals from biomass. In addition, process intensification by reducing the number of steps for final chemicals production by performing cascade-type catalytic reactions in one-pot mode is largely desirable in a biorefinery facility. In this review the possibilities of valorization of representative platform molecules such as sugars, itaconic and levulinic acids and furanic aldehydes through one-pot cascade processes using mono and multifunctional heterogeneous catalysts are illustrated through selected examples.

A catalyst-free synthesis of various 2-alkyl or aryl-substituted benzothiazoles and benzimidazoles has been developed at room temperature by simply combining alkyl or arylaldehydes with ortho-phenylenediamines and 2-aminothiophenols, respectively. The synthesis of these widely applicable fused heterocycles is often challenging and requires additives. The advantages of this new benign procedure include: products with nearly quantitative yields, high atom economy and no toxic waste formation, catalyst-free process with no need for catalyst separation and/or recycling, the use of a green and sustainable solvent, ethanol, and mostly room temperature reactions with moderate reaction times to ensure that the protocol is energetically favorable.