Perchlorate Hexahydrate Research Articles

Zinc perchlorate catalyzed one-pot synthesis of 3,4-dihydropyrimidinones under solvent-free conditions

In this paper, we report zinc perchlorate hexahydrate [Zn(ClO4)2•6H2O] as a highly effective catalyst for the synthesis of 3,4-dihydropyrimidin-2(1H)-ones under solvent-free conditions. These improved reaction conditions allow the preparation of a wide variety of substituted dihydropyrimidinones in high yields and purity under mild reaction conditions. Compared with the classical Biginelli reaction, this method has the advantage of excellent yields and short reaction time in solvent-free conditions.

Unusual complexation of Cu(I) by pyrimidine/pyridine-pyrazole derived ligands exploiting the molecular function of 2-mercapto-4,6-dimethylpyrimidine – Syntheses, crystal structures and electrochemistry

Reaction of 2 equiv. amount of copper(II) chloride dihydrate with 2 equiv. of methyl-5-methyl-1-(4,6-dimethyl-2-pyrimidyl)pyrazole-3-carboxylate (DpymPzC) in presence of 1 equiv. of 2-mercapto-4,6-dimethylpyrimidine (DpymtH) at pH ∼ 6 afforded the tricoordinated copper(I) complex [Cu(DpymPzC)Cl] ( 1). The same reaction with copper(II) perchlorate hexahydrate, as the metal salt under the same equivalent ratio at pH ∼ 6 formed the tetracoordinated copper(I) complex [Cu(DpymPzC) 2]ClO 4 ( 2). In both the cases, the role of DpymtH is nothing but only to reduce the copper(II) salt in situ finally forming the copper(I) complex. On the other hand, the direct reaction between the copper(I) thiocyanate and DpymPzC in 2:2 equiv. ratio produced a tricoordinated copper(I) complex [Cu(DpymPzC)SCN] ( 3). In a similar reaction of 2 equiv. amount of copper(II) chloride dihydrate with 2 equiv. amount of ethyl-5-methyl-1-(2-pyridyl)pyrazole-3-carboxylate (PyPzC) in presence of 1 equiv. of DpymtH at pH ∼ 6, an intense red coloured microcrystalline compound ( 4) was obtained. In contrast, 1 equiv. of PyPzC and 2 equiv. of DpymtH on reaction with 1 equiv. of copper(II) chloride dihydrate at pH ∼ 6 produced a novel tetranuclear mixed coordinated [Cu 4(DpymtH) 4Cl 4] complex ( 5). Here DpymtH plays dual role – a reducing agent for the copper(II) salt followed by a chelating ligand towards copper(I) so formed in situ. Among the above species, 1, 2 and 5 are crystallographically characterized. In 1, the central copper atom is in distorted triangular planar geometry with N 2Cl chromophore whereas in 2, the same is in distorted tetrahedral geometry with N 4 chromophore. Notably, the extent of distortion from the ideal geometry is more in 2. In 5, which is in chair conformation, out of four copper atoms, two being in S 2Cl chromophore are tricoordinated and the remaining two are tetracoordinated with NS 2Cl chromophore. The metal centers are bridged through DpymtH in its ‘thione’ form. Interestingly, the chelation (in part) results in formation of the highly stable four-membered two chelate rings around the two tetracoordinated copper atoms in 5. The two copper centers along the long arm of the chair are separated through a distance of 5.190 Å while those in the short arm are at a length of 3.629 Å. The electronic, IR spectra and electrochemistry of the complexes 1, 2 and 5 have also been investigated.

Copper perchlorate hexahydrate: a highly efficient catalyst for the cyanosilylation of aldehydes

AbstractCu(ClO4)2·6H2O has been found to be an efficient catalyst for cyanosilylation reaction of aldehydes in THF at room temperature with low catalytic loading (1.0 mol%) in short reaction time (mostly within 10 min). Copyright © 2008 John Wiley & Sons, Ltd.

Raman spectra of crystalline iron perchlorate hexahydrate

AbstractRaman studies of crystalline iron perchlorate hexahydrate (Fe(ClO4)2·6H2O) in the region of lattice and anion internal modes were carried out in the temperature range 80–385 K. The temperature‐dependent Raman results are consistent with those from previous works, showing that two phase transitions occur around 336 and 245 K. The transition at 336 K may be considered as an order–disorder transformation, while the one at 245 K is associated with the configurational disorder of the tetrahedron of the perchlorate ions. Copyright © 2008 John Wiley & Sons, Ltd.

Synthesis and Crystal Structure of Tetraethylammonium Tris(1,10-phenanthroline)manganese(II) triperchlorate (Et4N)[Mn(phen)3](ClO4)3

The title complex was serendipitously obtained by reacting imidazole-4,5-dicarboxylic acid, tetraethylammonium hydroxide, 1,10-phenanthroline, and manganese(II) perchlorate hexahydrate in ethanol-water mixed solvent. It crystallizes in the monoclinic system, space group Cc with a = 24.8043(6), b = 8.7973(2), c = 24.2475(2)A, β = 118.844(1)°, V = 4634.6(2)A3 and Z = 4. A most noteworthy structural feature is that two counterions, namely Et4N+ and ClO4- cocrystallize in the crystal lattice.

High-energy complex copper(II) perchlorate with 1,5-pentamethylenetetrasole as ligand

Possibility of obtaining an energy-saturated metal complex, copper tetrakis[cyclopentamethylenetetrasol] perchlorate, was studied by reacting copper(II) perchlorate hexahydrate with cyclopentamethylenetetrazol. The composition and structure of the complex were confirmed by elemental analysis and UV, IR, 1H NMR, and ESR spectroscopies. The thermal decomposition of the metal complex synthesized was analyzed and its explosive characteristics and combustion law, as well as the combustion law of a model formulation of a composite solid propellant with addition of the complex, were determined.

Zinc(II) Perchlorate Hexahydrate Catalyzed Opening of Epoxide Ring by Amines: Applications to Synthesis of (RS)/(R)‐Propranolols (XIV) and (RS)/(R)/(S)‐Naftopidils (XVI).

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Zinc(II) Perchlorate Hexahydrate Catalyzed Opening of Epoxide Ring by Amines: Applications to Synthesis of (RS)/(R)-Propranolols and (RS)/(R)/(S)-Naftopidils

Commercially available zinc(II) perchlorate hexahydrate [Zn(ClO4)2.6H2O] was found to be a new and highly efficient catalyst for opening of epoxide rings by amines affording 2-amino alcohols in high yields under solvent-free conditions and with excellent chemo-, regio-, and stereoselectivities. For unsymmetrical epoxides, the regioselectivity was influenced by the electronic and steric factors associated with the epoxides and the amines. A complementarity in the regioselectivity was observed during the reaction of styrene oxide with aromatic and aliphatic amines: aromatic amines provided amino alcohols from nucleophilic attack at the benzylic carbon as major products whereas aliphatic amines resulted in formation of the amino alcohols through reaction at the terminal carbon atom of the epoxide ring as the major/sole products. Reaction of aniline with various glycidic ethers gave the amino alcohols by regioselective nucleophilic attack at the terminal carbon atom of the epoxide ring as the only/major product. Zinc(II) perchlorate hexahydrate was found to be the best catalyst compared to other metal perchlorates. The counteranion modulated the catalytic property of the various Zn(II) compounds that followed the order Zn(ClO4)2.(6)H2O>>Zn(BF4)2 approximately Zn(OTf)2>>ZnI2>ZnBr2>ZnCl2>Zn(OAc)2>Zn(CO3)2 in parallelism with the acidic strength of the corresponding protic acids (except for TfOH). The applicability of the methodology was demonstrated by the synthesis of cardiovascular drugs propranolol and naftopidil as racemates and optically active enantiomers.

Synthesis and Crystal Structure of Tris(1,10-phenanthroline)iron(II) perchlorate ethanol monosolvate hemihydrate

The title complex was serendipitously obtained by reacting dipicolinic acid, 1,10-phenanthroline, and iron(III) perchlorate hexahydrate in ethanol. Single crystals were grown by allowing the sealed reaction mixture to stand for two weeks, thus yielding the increasingly structurally characterized tris(1,10-phenanthroline)iron(II) cation.

Photo-assisted synthesis of highly fluorescent ZnSe(S) quantum dots in aqueous solution

This paper describes the synthesis of highly water-soluble and fluorescent ZnSe(S)-alloyed quantum dots (QDs). We used zinc perchlorate hexahydrate, sodium hydrogen selenide as precursors and mercaptopropionic acid as stabilizer to synthesize ZnSe QDs in aqueous solution at 160 °C for 9 h. The as-prepared ZnSe QDs possess a quantum yield (QY) of 8.1% and high trapped emission. After UV irradiation using a 100 W Hg–Xe lamp for 0.5 h, ZnSe(S) QDs having a QY of 19.0% are formed from ZnSe QDs. However, aggregation of ZnSe(S) QDs under longer UV irradiation (> 0.5 h) takes place, leading to instability and irreproducibility. To overcome this, additional thiol compounds (mercaptopropionic acid, mercaptosuccinic acid, 11-mercaptoundecanoic acid, and thioglycolic acid) were separately added to ZnSe QD solutions during UV irradiation. UV irradiation and oxygen accelerate the release of S2− from the thiol compounds, leading to the formation of ZnSe(S) QDs. Among the thiol compounds, mercaptosuccinic acid is the most suitable in terms of stability and photoluminescence intensity. We suggest that the size and functional group of the thiol compounds play an important role in determining the optical properties and stability of ZnSe(S) QDs. The as-prepared ZnSe(S) QDs fluoresce strongly (QY up to 44.0%) at 407 nm with a narrow bandwidth (W1/2 < 25 nm) when excited at 325 nm.

Carboxyester hydrolysis promoted by Cu(II) complexes of pyridyl-amine carboxylate-pendant ligands

Multidentate ligands containing tripodal pyridyl-amine moieties tethered to a carboxylate group by alkyl linkers of varying lengths were synthesized to obtain a series of water-soluble ligands to elucidate the effects of the differing coordination environments on the properties of the resulting metal complexes. These new, water-soluble ligands, [bis-(2-pyridin-2-yl-ethyl)-amino]-acetic acid (L 1), 3-[bis-(2-pyridin-2-yl-ethyl)-amino]-propionic acid (L 2), 4-[bis-(2-pyridin-2-yl-ethyl)-amino]-butyric acid (L 3), and 6-[bis-(2-pyridin-2-yl-ethyl)-amino]-hexanoic acid (L 4), were treated with copper(II) perchlorate hexahydrate to yield the corresponding Cu(II) complexes, which have all been characterized by X-ray crystallography. L 1 binds Cu(II) to form the tetrameric complex {[Cu(μ- 1)][ClO 4] · 4H 2O} 4 ( 1) in the solid state, whereas the Cu(II) complexes of ligands L 2–L 4 form long-chain one-dimensional polymeric complexes {[Cu(μ-L 2)][ClO 4] · H 2O} n ( 2), {[Cu(μ-L 3)][ClO 4] · H 2O} n ( 3), and {[Cu(μ-L 2)][ClO 4] · H 2O} n ( 4), respectively, in the solid state. Complexes 1– 4 dissolved in 10% (v/v) CH 3CN aqueous solution were tested for their ability to promote the hydrolysis of the activated ester compound 4-nitrophenylacetate (NA), with 3 being the most active complex and 1 being the least active, possibly due to differences in the ability of the carboxylate moiety to act as either a general base or a nucleophile in the hydrolysis of NA as dictated by the tether length. The p K a values of the copper-bound aquo ligands in solution were measured by spectrophotometric titration.

Zinc perchlorate hexahydrate [Zn(ClO 4) 2·6H 2O] as acylation catalyst for poor nucleophilic phenols, alcohols and amines: Scope and limitations

Commercially available zinc perchlorate hexahydrate [Zn(ClO 4) 2·6H 2O] was found to be a highly efficient catalyst for acylation of electron deficient phenols, sterically hindered alcohols and electron deficient and sterically hindered amines. The acetylated derivatives were obtained in excellent yields under solvent-free conditions and at room temperature. However, the reaction of highly electron deficient and sterically hindered phenol, e.g., 2,4-dinitrophenol required heating at 80 °C. In case of reactions with alkoxy or dialkoxy benzylic alcohols, a complex product mixtures were formed containing the corresponding dibenzylic ethers. The catalyst was found to be of general use with respect to other acylating agents such as propionic, iso-butyric, pivalic, benzoic and chloroacetic anhydrides. However, the rate of acylation was influenced by the steric and electronic factors of the anhydrides and followed the order Ac 2O > (PhCO) 2O > (EtCO) 2O > ( i PrCO) 2O > ( t BuCO) 2O ≫ (ClCH 2CO) 2O. Benzoylation and pivalation of phenols (including electron deficient phenols), dihydric phenol and sterically hindered alcohol afforded excellent yields. The catalytic activity of various zinc compounds was found to be of the order Zn(ClO 4) 2·6H 2O > ZnI 2 ∼ ZnBr 2 > ZnCl 2 ≫ Zn(OAc) 2 > ZnCO 3 and was parallel to the acidic strength of the corresponding protic acids.

Zinc perchlorate hexahydrate as a new and highly efficient catalyst for synthesis of 2-hydroxysulfides by opening of epoxide rings with thiols under solvent-free conditions: Application for synthesis of the key intermediate of diltiazem

Commercially available zinc perchlorate hexahydrate [Zn(ClO 4) 2·6H 2O] was found to be highly effective catalyst for opening of epoxide ring by thiols under solvent-free condition at room temperature for efficient synthesis of 2-hydroxysulfides. The catalytic activity of various group I/II metal perchlorates followed the order Zn(ClO 4) 2·6H 2O ≫ Mg(ClO 4) 2·6H 2O > Ba(ClO 4) 2·6H 2O ⋙ LiClO 4. The Zn(ClO 4) 2·6H 2O-catalysed reaction of epoxides derived from cyclic and acyclic olefines with thiols afforded β-hydroxysulfides in high yields. Reaction with cycloalkene oxides led to stereoselective formation of the trans-2-hydroxysulfides. Excellent regioselectivity was observed for unsymmetrical epoxides. In case of styrene oxide, the hydroxysulfide from nucleophilic attack at the benzylic carbon of the epoxide was the major product. Preferential nucleophilic attack by thiophenol took place at sterically less hindered position of the epoxide ring of unsymmetrical non-styrenoid alkene oxides. Epichlorohydrin exemplified a case of chemo- and regioselective reaction with no detectable (GC–MS) side product formation by direct displacement of the chlorine atom. The methodology was extended for an efficient synthesis of the key intermediate of diltiazem.

New findings in the catalytic activity of zinc glutarate and its application in the chemical fixation of CO 2 into polycarbonates and their derivatives

A heterogeneous zinc glutarate (ZnGA) catalyst and its derivatives were prepared from various zinc and glutarate sources. The hydrothermal reaction between zinc perchlorate hexahydrate and glutaronitrile afforded ZnGA single crystals ( sc-ZnGA), with a monoclinic lattice unit cell and a P2/ c space group, as determined by X-ray single-crystal structural analysis. The structural details of the ZnGA catalyst are crucial in helping to elucidate its activity in the copolymerization reactions between carbon dioxide (CO 2) and alkylene oxides. X-ray absorption studies provided direct evidence that CO 2 and propylene oxide (PO) are reversibly adsorbed onto the Zn ion centers on the ZnGA surface. Compared to CO 2, PO was found to insert more easily into the Zn–O bond of the ZnGA catalyst, suggesting that the ZnGA-catalyzed copolymerization is initiated by PO rather than CO 2. The activity of the ZnGA catalyst in the copolymerization of CO 2 and PO was found to depend on the zinc source used, and its ability to produce a catalyst of large surface area and high crystallinity (≥77%). Modification of the glutarate ligand with electron-donating or withdrawing substituents failed to enhance the ZnGA catalyst activity further, indicating that glutarate is the best ligand for the Zn metal ion to achieve a high catalytic activity in the CO 2 copolymerization with PO. The ZnGA-catalyzed copolymerization was further optimized to maximize the yield of alternating poly(propylene carbonate), and also extended to the terpolymerization of CO 2 and PO with δ-valerolactone (VL). Terpolymers with high molecular weights and yields could be obtained by adjusting the PO/VL feed ratios. In addition, the terpolymers were found to exhibit excellent enzymatic and biological degradability.

Monomers, chains, ladders, and two-dimensional sheets: Structural diversity in six new compounds of Zn(II) with 4,4′-bipyridine

Six new zinc(II)–4,4′-bipyridine coordination polymers with diverse structural topologies are reported. The reaction of one equivalent of zinc(II) perchlorate hexahydrate with three equivalents of 4,4′-bipyridine (bipy) under hydrothermal conditions produces a mixture of [Zn(4,4′-bipy) 2(H 2O) 4](ClO 4) 2 · 2(4,4′-bipy) ( 1), [Zn 3(4,4′-bipy) 4(OAc) 4](ClO 4) 2 · 2(H 2O) ( 2), and [Zn 3(4,4′-bipy) 3(OAc) 4(H 2O) 2](ClO 4) 2 · (H 2O) ( 3) (OAc = acetate), for which single crystals can be isolated. Compound 1 contains sheet-like arrays of discrete monomers co-crystallized with uncoordinated bipy molecules to form extended triangular channels containing counterions. Compounds 2 and 3 consist of acetate-bridged zinc trimers linked by bipy to form three-leg ladders that are isolated in 3 and further linked by bipy into two-dimensional networks in 2. The reaction of one equivalent of zinc(II) perchlorate hexahydrate with 1.5 equivalents of bipy in dimethyl sulfoxide yields single crystals of [Zn(4,4′-bipy)(ClO 4)(H 2O)(OH)] ( 4) and [Zn(4,4′-bipy)(DMSO) 4](ClO 4) 2 ( 5) while crystals of [Zn(4,4′-bipy) 3(DMSO) 2](ClO 4) 2] · 2(4,4′-bipy) · (H 2O) ( 6) are obtained from DMSO with three equivalents of bipy. Compound 4 is a mutually interpenetrated network of hydrogen-bonded, one-dimensional Zn–bipy zig-zag chains and compound 5 exists as isolated, linear chains. Compound 6 also contains linear chains, linked in three-dimensions by π-stacking interactions between bipy ligands and guests.

Hexaaquairon(III) perchlorate trihydrate

A single crystal of commercially available `iron(III) perchlorate hexahydrate' has been structurally characterized and shown to be hexaaquairon(III) tris(perchlorate) trihydrate, [Fe(H2O)6](ClO4)3·3H2O. The structure contains [Fe(H2O)6]3+ complex ions, charge-balancing perchlorate ions and three water molecules of crystallization per Fe atom. A network of O—H...O hydrogen bonds helps to stabilize the crystal packing. Fe, Cl and one water O atom occupy special positions with site symmetries \overline{3}, 2, and 2, respectively.

Zinc Perchlorate Hexahydrate Catalyzed Conjugate Addition of Thiols to α,β‐Unsaturated Ketones.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Enantioselective Enol Lactone Synthesis under Double Catalytic Conditions

Under the ‘double-catalytic condition’ protocol using the (R,R)-DBFOX/Ph complex of nickel(II) perchlorate hexahydrate and tetra­methyl-piperidine, enol lactones were formed with high enantioselectivity. The mechanism proceeds via an enantioselective Michael addition followed by enolization of the diketone moiety, then cyclization with concomitant displacement of the pyrazole auxiliary. Catalyst loadings can be reduced to 2 mol% and use of β-hydroxy-lactones instead of the diketone is also reported.

Zinc Perchlorate Hexahydrate Catalysed Conjugate Addition of Thiols to α,β-Unsaturated Ketones

Zn(II) perchlorate hexahydrate has been found to be a new and efficient catalyst for conjugate addition of thiols to α,β-unsaturated ketones under solvent-free conditions at room temperature. The reaction of aryl, arylalkyl and alkyl thiols with cyclic and acyclic α,β-unsaturated ketones takes place affording excellent yields after five minutes to six hours. The compatibility of Zn(ClO 4 ) 2 .6H 2 O with different solvents provides a means to carry out the reaction under versatile experimental conditions. The rate of thiol addition was dependent on the electronic and steric factors of the enones and the thiols. The substituent at the β-carbon of the α,β-unsaturated ketone substrate caused steric hindrance during conjugate addition and required longer reaction times. The rate of reaction for alkane thiols e.g. ethanethiol was sluggish compared to that of aryl thiols.

Highly Efficient Solvent-Free Condensation of Carboxylic Acids with Alcohols Catalysed by Zinc Perchlorate Hexahydrate, Zn(ClO4)2?6?H2O

Zinc perchlorate hexahydrate, Zn(ClO4)2⋅6 H2O, efficiently catalyses the esterification between nearly equimolar amounts of carboxylic acids and alcohols. The reaction works under solvent-free conditions at relatively low temperatures. Excellent results were obtained with a wide range of substrates.