Synthesis of 2-iminothiazolidin-4-ones using guanine functionalized SBA-16 as a solid base catalyst

Mesoporous SBA-16/SO3H from waste sugarcane bagasse ash for efficient Biginelli reactions

Sustainable, sulfonated mesoporous SBA-16 catalysts were synthesized from sugarcane bagasse ash (SCBA), an abundant agro-industrial waste from bio-energy production. SBA-16 modification with 3-mercaptopropyltrimethoxysilane (MPTMS) and subsequent oxidation to incorporate sulfonic acid groups, significantly enhanced the textural properties, achieving a surface area of 207 m2/g, while trace impurities from SCBA may enhance Lewis acidity. Such features improved catalytic efficiency and sustainability. A green assessment of catalyst synthesis from SCBA using the DOZN™ Green Chemistry Evaluator revealed that the SCBA-based methods are more sustainable than conventional TEOS-based methods. This study represents the first application of sulfonated SBA-16 for Biginelli reactions, yielding 99% for the reaction between benzaldehyde, methyl acetoacetate, and urea (at 105 °C, 7 h, 10 wt% catalyst, in ethanol). Catalysts demonstrated exceptional durability, with negligible loss of activity (~ 98%) over five consecutive cycles, highlighting its suitability for this application. SBA-16 catalysts exhibited broad substrate compatibility, particularly with electron-withdrawing groups across various aldehydes and β-diketones. The Biginelli reactions aligned with green chemistry principles, achieving favorable values for process mass intensity (PMI: 11.86-33.32 g/g), E-factor (10.86-32.32 g/g), solvent intensity (SI: 9.69-14.50 g/g), and water intensity (WI: 3.28-9.36 g/g). The Green Motion sustainability assessment tool score was 75/100. Sulfonated SBA-16 catalysts offer a sustainable alternative to commercial silica, with superior performance, reduced catalyst loading, and minimized environmental impact, underscoring its potential for use in industrial applications.

Applications of catalytic systems containing DNA nucleobases (adenine, cytosine, guanine, and thymine) in organic reactions

In recent years, nucleobases have attracted special attention because of their abundant resources and multiple interaction sites, which enable them to interact with and functionalize other molecules. This review focuses on the catalytic activities of each of the four main nucleobases found in deoxyribonucleic acid (DNA) in various organic reactions. Based on the studies, most of the nucleobases act as heterogeneous catalytic systems. The authors hope their assessment will help chemists and biochemists to propose new procedures for utilizing nucleobases as catalysts in various organic synthetic transformations. The review covers the corresponding literature published till the end of August 2023.

Cucurbit[6]uril-Supported Fe3O4 Magnetic Nanoparticles Catalyzed Green and Sustainable Synthesis of 2-Substituted Benzimidazoles via Acceptorless Dehydrogenative Coupling

A new composite, cucurbit[6]uril (CB[6])-supported magnetic nanoparticles, Fe3O4-CB[6], was synthesized via a co-precipitation method in air and fully characterized by Fourier transform infrared spectroscopy, powder X-ray diffraction, X-ray photoelectron spectroscopy, field-emission scanning electron microscopy, high-resolution transmission electron microscopy, energy-dispersive X-ray spectroscopy, thermogravimetric analysis, inductively coupled plasma-mass spectrometry, and vibrating sample magnetometry techniques. It has been found to be a highly efficient, economic, and sustainable heterogeneous catalyst and has been employed for the first time for the synthesis of a series of biologically important 2-substituted benzimidazoles from various benzyl alcohols and 1,2-diaminobenzenes under solvent-free conditions via acceptorless dehydrogenative coupling to afford the corresponding products in good to excellent yields (68-94%). The magnetic nature of the nanocomposite facilitates the facile recovery of the catalyst from the reaction mixture by an external magnet. The catalyst can be reused up to five times with negligible loss in its catalytic activity. All the isolated products were characterized by 1H and 13C{1H} NMR spectroscopy.