10.1016/S0040-4020(00)00626-8
The study presents an eco-friendly and cost-effective method for the tosylation of alcohols and selective monotosylation of diols using p-toluenesulfonic acid with metal-exchanged montmorillonite clay as a catalyst. The Fe3+-montmorillonite clay demonstrated the highest effectiveness among the tested catalysts, outperforming Zn2+, Cu2+, Al3+-exchanged montmorillonites and K10 montmorillonite. This method allows for the regioselective tosylation of diols to monotosylated derivatives with high purity, favoring the primary hydroxy group in the presence of secondary hydroxy groups. The catalyst's reusability over several cycles was consistent, as shown in the tosylation of cyclohexanol. This approach minimizes by-product formation, typically just water, and offers advantages such as ease of catalyst recovery, recyclability, and enhanced stability compared to traditional methods using sulfonyl chloride or anhydride with organic bases.
10.1007/s11164-018-3659-7
This study presents the synthesis of montmorillonite (MMT) supported Fe3O4 magnetic nanoparticles, which were used as heterogeneous nanocatalysts for the one-pot synthesis of indeno[1,2-b]indolone derivatives in aqueous media. The MMT@Fe3O4 nanocomposites were characterized using various techniques including X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), vibrating sample magnetometer (VSM), thermogravimetric analysis (TGA), and Fourier transform infrared spectroscopy (FT-IR). The catalyst exhibited high efficiency in promoting the cyclocondensation of ninhydrin, 1,3-diketone compounds, and amine derivatives to generate the desired indeno[1,2-b]indolone derivatives in excellent yields under mild conditions. This study highlights the advantages of using MMT@Fe3O4 as an environmentally friendly, cost-effective, and recyclable catalyst, providing a green and efficient approach for the synthesis of these heterocyclic compounds of biological and pharmacological importance.
10.1039/c3ra42749h
The research focuses on the development and characterization of heterogeneous catalysts composed of Mn-montmorillonite coordinated with novel Schiff-base ligands for the epoxidation of cyclohexene using molecular oxygen under Mukaiyama conditions. The catalysts were synthesized and characterized using various analytical techniques including IR, UV-vis DRS, XRD, SEM, and ICP. The study optimized reaction conditions to achieve high conversion rates and selectivity for the production of epoxycyclohexane, with the best results showing 100% conversion and 90.0% selectivity at 40°C in 5 hours using molecular oxygen as the oxidant in acetonitrile. The catalysts demonstrated stability over at least three cycles, indicating their potential as environmentally friendly and economical options for industrial epoxidation processes. The reactants involved in the catalytic epoxidation reaction included cyclohexene, isobutylaldehyde, and the Mn-montmorillonite composite catalysts. The analysis of the reaction involved the use of GC-MS and GC equipped with specific columns to determine the conversion and selectivity of the epoxide product.
