Deprotection Chemistry Mediated by ZrOCl2 · 8H2O: An Efficient,Mild, and Green Method for the Conversion of Oximes to Carbonyl Compounds in Aqueous Acetone

Abstract

Less-toxic, moisture-stable, inexpensive, and ecofriendly zirconium oxychloride octahydrate (ZrOCl₂ · 8H₂O) in aqueous acetone (1:1) mediates the conversion of oximes to carbonyl compounds in moderate to good yields. This green methodology is applicable to both aldoximes and ketoximes with tolerance to >C?C<, -NO₂, -OH, and -Cl groups. The reaction and workup are simple.

Protection and deprotection chemistry catalyzed by zirconium oxychloride octahydrate (ZrOCl2·8H2O)

Abstract

An efficient, chemoselective, convenient, and straightforward methodology has been developed for the protection of C=O group of aldehydes/ketones as C=N moiety of hydrazones catalyzed by ZrOCl₂·8H₂O (10 mol%) in acetonitrile and the same catalyst in methanol oxidatively cleaves C=N moiety of hydrazones to provide parent carbonyl compounds in high yields. The reactions have been performed in aerobic condition. The catalyst is inexpensive, readily available, easy to handle, insensitive to air and moisture, easily recoverable and can be reused and importantly less toxic.     

ZrOCl2·8H2O: An Efficient Catalyst for One-Pot Synthesis of α-Amino Phosphonates Under Solvent-Free Conditions

A highly efficient protocol has been developed for the three-component reaction of an amine, an aldehyde, and diethyl phopshite catalyzed by ZrOCl₂·8H₂O, an environmentally friendly catalyst, at ambient temperature. The catalyst exhibited remarkable activity and tolerated a wide variety of functional groups, providing the desired amino phosphonates in excellent yields under solvent-free conditions. Alternatively, the reaction rate can be significantly enhanced by carrying out the reaction in a monomode microwave reactor as a promoter.     

ZrOCl2 · 8H2O as an Efficient Reagent for the Solvent‐Free Synthesis of 3,4‐Dihydropyrimidin‐2‐(1H)‐ones

ZrOCl₂ · 8H₂O, a commercially available reagent, can be used for the promotion of the synthesis of 3,4‐dihydropyrimidin‐2(1H)‐ones under solvent‐free reaction conditions. All reactions were performed at 90°C in good to high yields.     

A Mild and Efficient Deprotection of Geminal Diacetates Catalyzed by FeCl3 ·6H2O in Ionic Liquid

The selective deprotection of geminal diacetates promoted by FeCl3·6H2O in the ionic liquid [bmim] [BF4] canbe efficiently achieved in good yields. The ionic liquid and the catalyst can be recycled easily and the process is car ried out under mild conditions.     

Highly anti–anti selective synthesis of bis-β-amino ketones via three-component direct Mannich-type reaction of terephthalaldehyde catalyzed by ZrOCl2·8H2O

At room temperature, zirconium oxychloride (ZrOCl₂·8H₂O) efficiently catalyzes the direct Mannich-type reaction of a variety of in situ generated bis-imines using terephthalaldehyde and anilines with ketones in a three-component reaction at room temperature. The reaction proceeds rapidly and affords the corresponding bis-β-amino ketones in good-to-high yields with good-to-excellent anti–anti selectivity.     

Crystal Structure and Dynamics of Water Molecules and Fluoride Ions in NaKSbF5·1.5H2O and NaRbSbF5·1.5H2O

The atomic structures of crystal hydrates were determined at 173 and 293 K for NaKSbF₅·1.5H₂O (I) and at 293 K for NaRbSbF₅·1.5H₂O (II). Crystals I and II are isostructural, space group . The dynamics of water molecules and complex ions was investigated by NMR in the range 170-440 K. The existence of a phase transition of order–disorder type in compounds I and II was established. A mechanism leading to the diffusion motion of fluoride ions in II is suggested, and dehydration of the compounds is considered.     

SDS/Ac2O/H2O: Surfactant‐Mediated Cleavage of Imines with Acetic Anhydride to Carbonyls and Acetanilides in Water

Surfactant (SDS)‐mediated cleavage of imines was achieved with acetic anhydride to the corresponding carbonyls (aldehydes and ketones) and acetanilides in water at 25–30°C with very good to excellent yields, thus contributing significantly to the green chemistry concept.     

Intercalation of primary diamines in the lamellar niobate HNb3O8 · H2O

The intercalation of alkyl diamines in the protonic oxide HNb₃O₈ · H₂O is quantitative for the diamines H₂N(CH₂)_nNH₂ with n ranging from 2 to 10. All the intercalated oxides [H₃N(CH₂)_nNH₃]_0.5Nb₃O₈ · yH₂O are hydrated at room temperature; they can be easily and reversibly dehydrated to the oxides [H₃N(CH₂)_nNH₃]_0.5Nb₃O₈. The structural behavior of those compounds is compared to that of the alkyldiammonium titanoniobates [H₃N(CH₂)_nNH₃]_0.5TiNbO₅. An interpretation of their structural properties is given which takes into account the tendency of amines to assume an orientation transverse to oxide layers, the conformation of the amine chains, and the tendency to form dense organic layers.     

Mg(NTf2)2·xH2O: An Efficient Catalyst for the Synthesis of Homoallylic Alcohols in Water

An efficient method has been developed for the allylation of aldehydes with allytributylstannane in the presence of a catalytic amount of Mg(NTf₂)₂·xH₂O at room temperature in water to afford the corresponding homoallylic alcohols in good yields.     

ZrOCl2·8H2O catalyzed one-pot synthesis of 2,4,5-triaryl-1H-imidazoles and substituted 1,4-di（4,5-diphenylimidazolyl）benzene

A simple one-pot synthetic method for the preparation of 2,4,5-triaryl-lH-imidazoles from benzoin or benzil, ammonium acetate, aromatic aldehydes, and ZrOCl2-8H2O catalyst is described. The ZrOCl2-8H2O catalyst was found to be equally effective for aromatic and heteroaromatic aldehydes and also for the preparation of substituted 1,4-di（4,5-diphenylimidazol-yl） benzene.     

ZrOCl2·8H2O as an efficient and recyclable catalyst for the clean synthesis of xanthenedione derivatives under solvent-free conditions

ZrOCl₂·8H₂O was found to be an efficient and recyclable catalyst for the reaction of aromatic aldehydes with dimedone to afford 1,8-dioxo-1,2,3,4,5,6,7,8-octahydroxanthenes under solvent-free conditions. Short reaction time, excellent yields and simple work-up are the advantages of this procedure. The interaction obtained from XRD studies was shown that the catalyst loses H₂O during the reaction but it did not affect catalytic activity of the catalyst and the catalyst could be reused several times.     

Efficient Solar-Driven Water Harvesting from Arid Air with Metal–Organic Frameworks Modified by Hygroscopic Salt

Freshwater scarcity is a global challenge threatening human survival, especially for people living in arid regions. Sorption-based atmospheric water harvesting (AWH) is an appealing way to solve this problem. However, the state-of-the-art AWH technologies have poor water harvesting performance in arid climates owing to the low water sorption capacity of common sorbents under low humidity conditions. We report a high-performance composite sorbent for efficient water harvesting from arid air by confining hygroscopic salt in a metal–organic framework matrix (LiCl@MIL-101(Cr)). The composite sorbent shows 0.77 g g⁻¹ water sorption capacity at 1.2 kPa vapor pressure (30 % relative humidity at 30 °C) by integrating the multi-step sorption processes of salt chemisorption, deliquescence, and solution absorption. A highly efficient AWH prototype is demonstrated with LiCl@MIL-101(Cr) that can enable the harvesting of 0.45–0.7 kg water per kilogram of material under laboratory and outdoor ambient conditions powered by natural sunlight without optical concentration and additional energy input.     

Spin-Enhanced O−H Cleavage in Electrochemical Water Oxidation

Herein we report the vital role of spin polarization in proton-transfer-mediated water oxidation over a magnetized catalyst. During the electrochemical oxygen evolution reaction (OER) over ferrimagnetic Fe₃O₄, the external magnetic field induced a remarkable increase in the OER current, however, this increment achieved in weakly alkaline pH (pH 9) was almost 20 times that under strongly alkaline conditions (pH 14). The results of the surface modification experiment and H/D kinetic isotope effect investigation confirm that, at weakly alkaline pH, during the nucleophilic attack of Fe^IV=O by molecular water, the magnetized Fe₃O₄ catalyst polarizes the spin states of the nucleophilic attacking intermediates. The spin-enhanced singlet O−H cleavage and triplet O−O bonding occur synergistically, which promotes the O₂ generation more significantly than the strongly alkaline case involving only spin-enhanced O−O bonding.     

DTA-TG and XRD study on the reaction between ZrOCl2·8H2O and (NH4)2HPO4 for synthesis of ZrP2O7

In this paper, we report results of thermoanalytical investigation on the reaction between ZrOCl₂·8H₂O and (NH₄)₂HPO₄ in molar ratio 1:2. Differential thermal-thermogravimetric and X-ray diffraction analyses were performed in order to reveal the chemical transformations, which took place during heating of the individual compounds ZrOCl₂·8H₂O, (NH₄)₂HPO₄ and the mixture ZrOCl₂·8H₂O:2(NH₄)₂HPO₄. It was shown that the transformations in the mixture below 160 °C were connected with dehydration of ZrOCl₂·8H₂O and interaction between the components of the mixture, which resulted in the formation of NH₄Cl, NH₄H₂PO₄ and a mainly amorphous zirconium phase, most likely t-ZrO₂. The zirconium component subsequently reacted with ammonium dihydrophosphate (below 200 °C) or with dehydrated phosphate derivatives (above 200 °C), which in both cases yielded an amorphous product. The interaction between the components of the mixture resulting in the formation of ZrP₂O₇ was completed by its crystallisation at 610 °C. Our study indicates an alternative low-temperature approach for the synthesis of the technologically important ZrP₂O₇ material.     

Spectral studies on Ag8+ ions irradiated LAHCl·H2O and LAHBr·H2O single crystals

L-arginine hydrochloride monohydrate and L-arginine hydrobromide monohydrate single crystals are irradiated by 100 MeV Ag8+ swift heavy ions. The residual gases liberated from the irradiated samples are monitored as a function of ion fluence using quadrupole mass analyzer. The C2H3+, C2H2, N2, CO, HCl and CO2 are the dominant gases liberated. Fourier transform infrared spectra of irradiated crystals explain the breaking of bonds in a localized region of the crystals. The crystallinity of irradiated crystals is analyzed by powder X-ray diffractions.     

Thermal Transformations of CuNH4PO4⋅H2O

The isothermal and non-isothermal transformations of polycrystalline CuNH₄PO₄⋅H₂O in vacuum and in various gas atmospheres (in open air and in gaseous ammonia atmosphere) were studied at 20–800°C by means of differential thermal analysis, thermogravimetry, X-ray diffraction, paper chromatography, optical microscopy and chemical analyses. The effects of the gas phase composition on the kinetic peculiarities of total gas evolution and on the partial processes of dehydration, ammonia removal and rearrangement of the anionic sub-lattice were considered. This revised version was published online in August 2006 with corrections to the Cover Date.     

Highly Efficient Esterification of an Equimolar Amount of Carboxylic Acids and Alcohols Catalyzed by ZrOCl_2·8H_2O

Esterification of carboxylic acids with alcohols is one of the most fundamental and useful transformations in organic synthesis. The most common catalysts are H2SO4 and TsOH. However, H2SO4 or TsOH-catalyzed esterification procedure has some problems such as corrosion, side reactions, difficulty in separation. Hence, recently, various solid acid catalysts such as ion-exchanged resins, molecular sieve, and heteropoly acids etc. have been employed for esterification reaction. However, the s…