Current Organocatalysis - Volume 5, Issue 2, 2018

Background: The principal goal of this review is to provide a detailed study of various modified zeolites as catalysts for the synthesis of diverse organic biologically active compounds. The use of zeolites in organic synthesis is noteworthy since they are compatible with the reactants, ecofriendly, non-toxic, non-corrosive, insoluble in many solvents, resistive at high temperatures, and reusable with high yield and purity. Methods: Zeolites are three dimensional structures of crystalline, micro porous, hydrated aluminosilicates of alkali and alkaline earth metals. Primary building blocks of zeolites are the basic tetrahedral anions, i.e. [SiO4]4- and [AlO4]5-. Based on the Si/Al ratios, zeolites are classified into three major divisions and the composition ratios present in them can be altered. Molecules within the diverse zeolites cavities can be trapped because of their electrostatic and Vander walls types of attractive forces. Nanocrystalline zeolites have larger surface areas with internal surface porosity. Results: As a result, an increase in the surface area of specific zeolites is possible and thus superior adsorption of reactant molecules on its surface may take place. The whole structural orientation results in characteristic catalytic property within the zeolite systems. Conclusion: Greater catalytic activity is achieved with polyvalent ions rather than monovalent ions. Interestingly, the yield of drug intermediates depends on various parameters of catalysts (i.e. zeolite porosity, surface area, properties of doped metal ions/complexes, Si/Al ratio, number of Lewis and Bronsted acid sites, etc.). Medium and large pore containing zeolite gives a higher yield of products in comparison to zeolite that has a small pore. In addition, a zeolite with a higher surface area and higher Si/Al ratio exhibits higher catalytic efficiency.

Background: The rising number of health problems and diseases leads to demands and medical advancement. These increasing demands have led us to work on catalysis which ultimately increases the yield of pharmaceutically important drugs. Methods: Synthesis of 9, 10-diarylacridine-1, 8-dione has been carried out by single-pot, efficient and environmentally benign Hantzsch condensation reaction, which includes three component reactants i.e. aldehyde, amine and 5, 5-Dimethyl-1, 3- cyclohexanedione (dimedone). Zeolite LTL has been synthesized and modified by using three different metal oxides i.e. SrO, CuO and Cr2O3. Comparative studies based on %yield at varying parameters have been performed with different metal oxide modified zeolite-LTL which signifies the catalytic efficiency of various metal oxides and H-form zeolite. The competency of nanoporous modified zeolite-LTL has also been observed under various parameters (i.e. different solvent, temperature, catalyst concentration, time interval and catalytic recycling) with respect to the percentage yield of various compounds. Results: The synthesized nanoporous zeolites have been characterized by the help of Fourier Transform Infrared Spectroscopy (FTIR), X-Ray Diffraction (XRD), BET Surface Area and Porosity Analysis and Scanning Electron Microscopy- Energy dispersive X-ray spectroscopy (SEM-EDX) while the structures of the drug derivatives have been confirmed by Fourier Transform Infrared Spectroscopy (FTIR), 1H-Nuclear Magnetic Resonance Spectroscopy (1H-NMR) and Liquid Chromatography-Mass spectrometer (LC-MS). XRD, FT-IR and BET studies confirmed that the structure of zeolite hadn’t deformed/altered by incorporation of metal oxide nanoparticles. Also, BET and XRD results confirmed the mesoporous structure of zeolite LTL. The reactivity was found highest in ethanol with HLTL at 90°C for 60 min. i.e. 89.88%. Conclusion: The main advantages were short reaction time, excellent yield, low catalyst loading, high purity of the products due to the heterogeneous and harmless properties of zeolite. The protonated form of zeolite was found to be highly reactive due to presence of high surface area and greater number of active acid sites (Bronsted Active sites). The expeditious yield has been achieved by using catalysts which can be helpful to fulfill the demands of increasing health problems. The recyclability, heterogeneous nature and thermal stability of zeolites also increase the merit of this protocol.

Enhancement the oxidation constant (Kox) of Vitacid-C (Vit-C) in potassium chromate catalyzed by phosphate was studied. Molecular mechanics calculations suggest that the potential energy of the optimum molecular geometric structure of Vit-C is at least ten times of magnitude more stable than the PE of the molecular geometric structure of the same matrix. The oxidation constant Kox of Vit-C by K2CrO4 catalyzed by different mineral acids and different phosphate buffer are computed and discussed. Background: Ascorbic acid can be easily degraded depending on several variables. It has been reported that the degradation kinetics are significant affected by many environment factors such as pH, temperature, light, and the presence of enzymes, oxygen, and metallic catalyzers. The multifaceted nature of the debasement instruments prevents the improvement of mechanistic models, and pseudo- kinetic model, for example, zero order, first- order or second- order kinetics are frequently connected so as to get a solid match to the test information. Methods: Stock solutions of Vit-C and potassium chromate (K2CrO4) (Aldrich), Milwaukee, WI) were prepared. Thermo Electron-Vision pro Software V 4.10 UV/Vis spectrophotometer (190-1100 nm) with 1.0 cm quartz cell (scan speed, 5.0 nms-1) was used for spectrophotometric measurements. Results: The absorption spectra of K2CrO4 (0.5 mmol L-1) in different mineral acids were recorded as shown in Fig. (2). The decrease of the absorbance at about λmax =350 nm with increasing the concentration of Vit-C was observed. A good linearity (r ≥ 0.98) of the plotting absorbance vs. Vit-C concentration at constant an oxidant and acid, the slope of this straight line corresponding to the oxidation constant (Kox). The Kox increases according to the following series. HClO4 > H2SO4 >HNO3 >HCl >H3PO4. Conclusion: The Vit-C -Na3PO4 complex is a more favorable for the oxidative degradation than the Vit-C-H3PO4 matrix. The molar absorpitivity (ε) of the third-derivative (D3) is more sense about threeorder (2.36x103) of magnitude higher than D0 order (normal spectra). The limit of detection can be as low as 4.93 ppm (mgL-1) of Vit-C without treatment. This is about eight times (8.21) lower than that reported previously The molar absorpitivity (ε) of the third-derivative (D3) is more sense about threeorder (2.36 x 103) of magnitude higher than the normal spectra (zero-order, D0). The oxidation constant Kox of Vit-C by K2CrO4 catalyzed by different mineral acids according to the following series: HClO4 > H2SO4 > HNO3 > HCl > H3PO4. The oxidation constant Kox of Vit-C by K2CrO4 catalyzed by different phosphate buffer were computed and discussed.

Background: Multicomponent reactions (MCRs) are one of the most revolutionary concepts in synthetic organic chemistry. By definition, an MCR is a convergent chemical process involving three or more reactants to fabricate products which retain all structural and substructural features of the starting materials. The value of MCRs lies in all areas of synthetic chemistry, as they offer shorter reaction time, uncomplicated process protocol and high yield. We here reported a novel, effortless, ecofriendly multi-component one-pot synthesis of potent 2,3-dihydroquinazoline-4(1H)-ones is disclosed. Methods: The method causes condensation of isatoic anhydride, ammonium salts and aromatic aldehydes in ethanol. The reaction further employs metal chloride catalyst and offers significant advantages including the use of green solvent and unsophisticated work-up methodology. Additionally, the method is of value owing to the excellent yield obtained by the reaction. Results: The multicomponent reaction of isatoic anhydride and ammonium chloride with various aldehydes was investigated in presence of ethanol at reflux for 1.5 h. The catalytic MCR of a substituted aldehyde with ammonium chloride and isatoic anhydride generates 10 products with percentage yield ranging from 84-95%. Conclusion: In a nutshell, it can be stated that indium chloride-catalyzed multi-component reaction is a novel and efficient method for the synthesis of 2,3-dihydroquinazoline-4(1H)-ones. Significant advantages of the method include the use of simple and readily available precursors, high yield and easy workup with short reaction times. Better reactivity of ammonium chloride and high catalytic activity of InCl3 is an added advantage while using ethanol as a green solvent renders the reaction an ecocompatible status.

Background: A nucleophilic substitution between hydroxylactam and diarylphosphine oxide was developed for synthesizing α-aminophosphine oxide. Methods: Without a catalyst, hydroxylactams reacted with diarylphosphine oxides smoothly to furnish a series of isoindolo-β-carboline-derived phosphine oxide. Result: Isoindolo-β-carboline-derived phosphine oxides were obtained in 70-99% yields under mild reaction conditions. Notably, only water was a by-product. The mechanism of the atom-economic synthetic process was also discussed. Conclusion: The synthetic process is simple, efficiency, atom-economic and with great practical worth.

Background: In the recent times, organo-nano catalysis has emerged as a growing field in catalytic science with widespread applications in organic synthesis. In the present article, we have focused on the preparation of an organo-nano catalyst and its application in the synthesis of pyranopyrazole derivatives. Method: The catalyst was fabricated by the functionalization of vitamin B1 on silica coated ferrite (Fe2O3@SiO2) nanoparticles and was characterized by different analytical techniques viz., FT-IR, TGA, TEM, SEM, EDX, VSM and powder XRD. This organo-nano catalyst was employed for the one-pot synthesis of pyranopyrazole derivatives from aromatic aldehyde / isatin, malononitrile, hydrazine hydrate and ethyl acetoacetate in water-ethanol mixture at room temperature stirring condtion. Results: A library of pyranopyrazole derivatives was synthesized by using a simple, efficient and environmentally benign protocol. The products obtained were pure with considerably higher yields (87- 98%). The catalyst was easily retrieved from the reaction mixture and reused up to six runs without any significant decrease in its catalytic activity. Conculsion: A simple eco-friendly method, mild reaction conditions, high product yields, short reaction times, easy catalyst recovery and recyclability make this synthetic approach an efficient and sustainable protocol.