o-Benzenedisulfonimide as a Recyclable Homogeneous Organocatalyst for an Efficient and Facile Synthesis of 4-Amidotetrahydropyran Derivatives Through Prins–Ritter Reaction

Innovative synthesis of nano-magnetic bio-organocatalysts from red mud waste for green polyhydroquinoline derivatives synthesis

The imperative of transforming waste materials into valuable nanomaterials via ecological recycling has emerged as a pivotal avenue for environmental stewardship. This research contributes to the "greening" of global chemical processes by introducing a magnetic biocatalyst derived from red mud waste. Emphasizing the use of glutamic acid as the second most effective step in obtaining a green catalyst is a key focus of this work. Leveraging cost-effective materials such as FeSO4, amino acid, and Fe2O3 isolated from red mud enhances the economic viability of the synthesized catalyst. Characterization of the newly developed nano-magnetic bio-organocatalysts was conducted using advanced spectroscopic techniques, including Fourier transform infrared (FT-IR), X-ray diffraction (XRD), Transmission Electron Microscopy (TEM), field emission scanning electron microscopy (FE-SEM), Brunauer-Emmett-Teller (BET), energy-dispersive X-ray spectroscopy (EDX), mapping, thermogravimetric analysis (TGA), and vibrating-sample magnetometers (VSM). The catalytic activity of Fe3O4@SiO2@(CH2)3@Gl was examined in the one-pot synthesis of polyhydroquinolines, showcasing short reaction times, high efficiency, ease of catalyst separation, and the potential for catalyst recycling as salient features of this work. This study pioneers the utilization of red mud waste for eco-friendly nanomaterial synthesis and underscores the economic and environmental significance of incorporating glutamic acid as a crucial element in the catalyst synthesis process.

Recent advances of Ritter reaction and its synthetic applications

This review provides a comprehensive survey of Ritter reactions from 2014 to 2020.

Tandem Prins cyclizations for the construction of oxygen containing heterocycles

Tandem Prins cyclization is a versatile method for the synthesis of fused/bridged/spirotetrahydropyran scaffolds. Therefore, it has become a powerful tool for the stereoselective synthesis of oxygen/nitrogen containing heterocycles. Indeed, previous review articles on Prins spirocyclization illustrate the synthesis of spirotetrahydropyran derivatives and the aza-Prins reaction demonstrates its application in the total synthesis of natural products. The current review is devoted specifically to highlight tandem Prins cyclizations for the construction of fused scaffolds and related frameworks with a particular emphasis on recent applications. The mechanistic aspects and the scope of the methods are briefly discussed herein.

Three-Component, Diastereoselective Prins-Ritter Reaction for cis-Fused 4-Amidotetrahydropyrans toward a Precursor for Possible Neuronal Receptor Ligands

Here, we report an unprecedented, highly diastereoselective Prins-Ritter reaction of aldehydes, homoallylic alcohols, and nitriles in a three-component coupling reaction for the synthesis of tetra-cis-substituted 4-amidotetrahydropyrans. In this study, the reaction was not only applied for carbohydrate-based heterobicycles but also for more complex heterotricycles, showing acceptable levels of conversion yield (42-97% BRSM) and exclusive diastereoselectivity. Furthermore, the latter heterotricycles were converted to nine analogues of our neuronal receptor ligands IKM-159 and MC-27. An in vivo assay by intracerebroventricular injection in mice suggested that the substituent at C9 of the novel analogues interferes with the molecular interactions with the AMPA receptor, which was originally observed in the complex of IKM-159 and the GluA2 ligand binding domain. Our research has thus shown the power of a multicomponent coupling reaction for the preparation of a structurally diverse compound collection to study structure-activity relationships of biologically active small molecules.

Synthesis of antiproliferative 13α-d-homoestrones via Lewis acid-promoted one-pot Prins-Ritter reactions of d-secosteroidal δ-alkenyl-aldehydes

A simple one-pot Prins-Ritter route was developed for the synthesis of 16-acylamino-17a-hydroxy-d-homoestrone 3-benzyl and 3-methyl ethers in the 13α-estrone series. The d-secosteroidal δ-alkenyl-aldehydes were allowed to react with different nitriles in the presence of BF3·OEt2 as a Lewis acid catalyst. Prins cyclizations afforded 17a-hydroxy-16-carbenium ions, which underwent Ritter reactions with nitriles, leading to 16α- or 16β-acylamino derivatives. A side-product in which a dihydro-1,3-oxazine was bridged to six-membered ring D at positions 16α,17aα was formed in each reaction. The antiproliferative properties of the novel 13α-d-homosteroids were determined on a panel of human adherent cancer cell lines (HeLa, MCF-7, T47D, MDA-MB-231, MDA-MB-361, A2780 and A431) by means of MTT (3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide) assays. Some compounds proved to be more effective (with submicromolar IC50 values) than the reference agent cisplatin. One of the most potent compounds substantially increased the rate of tubulin polymerization. Cell cycle analyses by flow cytometry indicated a concentration-dependent accumulation of the G2/M cell population.