FeNH4(SO4)2·12H2O (alum)-catalyzed preparation of 1,4-dihydropyridines: improved conditions for the Hantzsch reaction

Abstract  

FeNH₄(SO₄)₂·12H₂O (alum) efficiently catalyzes the one-pot three-component reaction of dimedone, aldehydes, and 3-aminocrotonate to afford 1,4-dihydropyridines. The work-up is easy, and the products are obtained in good to excellent yields and high purity.     

A facile and efficient method for synthesis of xanthone derivatives catalyzed by HBF4/SiO2 under solvent-free conditions

Abstract  

HBF₄/SiO₂ was used as an efficient, green, and inexpensive catalytic system for synthesis of 12-aryl or 12-alkyl-8,9,10,12-tetrahydro-11H-benzo[a]xanthen-11-one derivatives via a one-pot three-component reaction of aldehydes, 2-naphthol, and cyclic 1,3-dicarbonyl compounds. The reactions proceeded rapidly at 80 °C under solvent-free conditions and the desired products were obtained in good to excellent yields.     

Br?nsted-acidic ionic liquid [HO3S(CH2)4MIM][HSO4] as efficient and reusable catalyst for one-pot synthesis of β-acetamido ketones

Abstract  

Efficient and convenient synthesis of β-acetamido ketones has been achieved by one-pot reaction of acetophenone, aryl aldehydes, acetyl chloride, and acetonitrile in the presence of 3-methyl-1-(4-sulfonylbutyl)imidazolium hydrogensulfate [HO₃S(CH₂)₄MIM][HSO₄], a Br?nsted-acidic ionic liquid, as a green and reusable catalyst in solvent-free media at room temperature. The catalyst could be recycled and reused without noticeable decrease in catalytic activity.     

Crystal Structure of (H3O)4[(C2H5)4N]6 [Th2Cl4(H2O)12O]3[Re4Se4(CN)12]4

Crystals of the rhenium cluster complex (H₃O)₄[(C₂H₅)₄N]₆[Th₂Cl₄(H₂O)₁₂O]₃[Re₄Se₄(CN)₁₂]₄ are obtained in an acidic (HCl) aqueous solution by the reaction of cluster salt K₄[Re₄Se₄(CN)₁₂]·6H₂O with ThCl₄ and (C₂H₅)₄NCl. Single crystal X-ray analysis shows that the title compound is ionic and crystallizes in the cubic crystal system (a = 22.7322(3) ?, V = 11746.93(27) ?³, Z = 2, I4 3m space group, R = 0.0350). It contains [Th₂Cl₄(H₂O)₁₂O]²⁺ cations with two thorium atoms bonded to each other through the bridging oxygen atom forming an angle of 180° in the structure.     

New organically templated gallium oxalate-phosphate structures based on Ga4(PO4)4(C2O4) building unit

Five organic-inorganic hybrid gallium oxalate-phosphates, [Ga₂(PO₄)₂(H₂O)(C₂O₄)_0.5](C₃N₂H₁₂)_0.5(H₂O) (1), [Ga₂(PO₄)₂(C₂O₄)_0.5](C₂N₂H₁₀)_0.5(H₂O) (2), [Ga₂(PO₄)₂(C₂O₄)_0.5](C₃N₂H₁₂)_0.5 (3), [Ga₂(PO₄)₂(H₂PO₄)_0.5(C₂O₄)_0.5](C₄N₃H₁₆)_0.5 (H₂O)_1.5 (4) and [Ga_2.5(PO₄)_2.5(H₂O)_1.5(C₂O₄)_0.5](C₄N₃H₁₅)_0.5 (5), have been synthesized by using 1,3-diaminopropane, ethylenediamine and diethylene triamine as structure-directing agents under hydrothermal condition. The structures of 1-5 are based on Ga₄(PO₄)₄(C₂O₄) building unit made up from Ga₂O₈(C₂O₄) oxalate-bridging dimer and alternating PO₄ and GaO₄ tetrahedral units. Compound 1 is layered structure where the building units link together in the same orientation. Corner sharing of these similar layers result in three-dimensional (3-D) structure 2. However, in compound 3, the building units arrange in a wave-like way to generate two types of eight member ring (8MR) channels. Both 4 and 5 contain the layers where the building units have an opposite orientation. Those layers are linked by H₂PO₄ group and Ga(PO₄)(H₂O)₃ cluster, respectively, to form 3-D frameworks with 12MR large pore channels. Compounds 2-5 exhibit intersecting 3-D channels where the protoned amines are located.     

IR and Raman spectra of two layered aluminium phosphates Co(en)3Al3P4O16 · 3H2O and [NH4]3[Co(NH3)6]3[Al2(PO4)4]2 · 2H2O

The FT IR and FT Raman spectra of Co(en)₃Al₃P₄O₁₆ · 3H₂O (compound I) and [NH₄]₃[Co(NH₃)₆]₃[Al₂(PO₄)₄]₂ · 2H₂O (compound II) are recorded and analysed based on the vibrations of Co(en)₃³⁺, Co(NH₃)₆³⁺, NH₄⁺, Al---O---P, PO₃, PO₂ and H₂O. The observed splitting of bands indicate that the site symmetry and correlation field effects are appreciable in both the compounds. In compound I, the overtone of CH₂ deformation Fermi resonates with its symmetric stretching vibration. The NH₄ ion in compound II is not free to rotate in the crystalline lattice. Hydrogen bonding of different groups is also discussed.     

Hydroxy- and boronic-acid-functionalized carbosilanes: Synthesis and solid state structure of Si(C6H4-4-SiMe2((CH2)3OH))4

Consecutive synthesis methodologies for the preparation of carbosilanes (Ph)(Me)Si((CH₂)₃B(OH)₂)₂ (2), Si(C₆H₄-4-SiMe₂((CH₂)₃B(OH)₂))₄ (5), (Ph)(Me)Si((CH₂)₃OH)₂ (3), and Si(C₆H₄-4-SiMe_3−n((CH₂)₃OH)_n)₄ (6a, n = 1; 6b, n = 2; 6c, n = 3) are reported. Boronic acids 2 and 5 are accessible by treatment of (Ph)(Me)Si(CH₂CHCH₂)₂ (1) or Si(C₆H₄-4-SiMe₂(CH₂CHCH₂))₄ (4a) with HBBr₂·SMe₂ followed by addition of water, while 3 and 6 are available by the hydroboration of 1 or Si(C₆H₄-4-SiMe_3−n(CH₂CHCH₂)_n)₄ (4a, n = 1; 4b, n = 2; 4c, n = 3) with H₃B·SMe₂ and subsequent oxidation with H₂O₂.The single molecular structure of 6a in the solid state is reported. Representative is that 6a crystallized in the chiral non-centrosymmetric space group P2₁2₁2₁ forming 2D layers due to intermolecular hydrogen bond formation of the HO functionalities along the crystallographic a and c axes.     

Hydrothermal synthesis, crystal structure, and characterization of a new pseudo-two-dimensional uranyl oxyfluoride, [N(C2H5)4]2[(UO2)4(OH2)3F10]

A new uranyl oxyfluoride, [N(C₂H₅)₄]₂[(UO₂)₄(OH₂)₃F₁₀] has been synthesized by a hydrothermal reaction technique using (C₂H₅)₄NBr, UO₂(OCOCH₃)₂·2H₂O, and HF as reagents. The structure of [N(C₂H₅)₄]₂[(UO₂)₄(OH₂)₃F₁₀] has been determined by a single-crystal X-ray diffraction technique. [N(C₂H₅)₄]₂[(UO₂)₄(OH₂)₃F₁₀] crystallizes in the monoclinic space group P2₁/n (No. 14), with , , , β=98.88(3)°, , and Z=4. [N(C₂H₅)₄]₂[(UO₂)₄(OH₂)₃F₁₀] reveals a novel pseudo-two-dimensional crystal structure that is composed of UO₂F₅, UO₃F₄, and UO₄F₃ pentagonal bipyramids. Each uranyl pentagonal bipyramid shares edges and corners through F atoms to form a six-membered ring. The rings are further interconnected to generate infinite strips running along the b-axis. [N(C₂H₅)₄]₂[(UO₂)₄(OH₂)₃F₁₀] has been further characterized by elemental analysis, bond valence calculations, Infrared and Raman spectroscopy, and thermogravimetric analysis.     

Formation of [Cp2TiSbMe2]2, [Cp2TiSb(SiMe3)2]2 and [Cp2TiCl]2·2Mes4Sb2

Reactions of [Cp₂Ti(btmsa)] (btmsa = bis(trimethylsilyl)acetylene) with R₄Sb₂ (R = Me, Me₃Si) give [Cp₂TiSbMe₂]₂ (1) or [Cp₂TiSb(SiMe₃)₂]₂ (2) respectively. [Cp₂TiCl]₂·2Mes₄Sb₂ (3) is serendipitously formed from [Cp₂Ti(btmsa)] and Mes₂SbH containing NH₄Cl traces.     

[Zn(H2PO4)4] clusters and ∞[Zn2(HPO4)3(H2PO4)2] layers in two new zinc phosphates templated by [H2(4-amino-2.2.6.6-tetramethylpiperidine)] cations

Two zinc phosphates (ZnPO), [H₂(N₂C₉H₂₀)]·[Zn(H₂PO₄)₄] (I) and [H₂(N₂C₉H₂₀)]₂·[Zn₂(HPO₄)₃(H₂PO₄)₂]·H₂O (II), are synthesized under hydrothermal conditions using 4-amino-2.2.6.6-tetramethylpiperidine as organic template. I crystallizes in space group with , , , α=92.57(1)°, β=89.76(1)°, γ=102.16(2)°, and Z=2. Its structure, refined to R=0.029 and R_w=0.076 for 4279 independent reflections, consists of [Zn(H₂PO₄)₄]²⁻ clusters held together through strong hydrogen bonds to form pseudo-layers between which the doubly protonated amine molecules are inserted. II is monoclinic, C2, with , , , β=103.72(5)°, and Z=4 (R=0.079, R_w=0.268, 2477 independent reflections). The structure of II consists of _∞[Zn₂(HPO₄)₃(H₂PO₄)₂]⁴⁻ inorganic (2D) layers built up from vertex-sharing [ZnO₄] and [(H₂/H)PO₄] tetrahedra. Organic cations and water molecules ensure the connection between these layers via hydrogen bonds. It is shown that numerous (1D), (2D), e.g., [H₂(N₂C₉H₂₀)]₂·[Zn₂(HPO₄)₃(H₂PO₄)₂]·H₂O, and (3D) (ZnPO) result from the condensation of the [Zn(H₂PO₄)₄]²⁻ clusters.     

Understanding the role of an easy-to-prepare aldimine-alkyne carboamination catalyst, [Ti(NMe2)3(NHMe2)][B(C6F5)4]

A series of reactivity studies of the carboamination pre-catalyst [Ti(NMe₂)₃(NHMe₂)][B(C₆F₅)₄] as well as the preparation of other catalysts are reported in this work. Treatment of [Ti(NMe₂)₃(NHMe₂)][B(C₆F₅)₄] with the aldimines Ar′NCHtol (Ar′ = 2,6-Me₂C₆H₃, tol = 4-MeC₆H₄), and depending on the reaction conditions, results in isolation of [Me₂NCHR′][B(C₆F₅)₄] (1) or (Me₂N)₂CHtol, as well as the asymmetric titanium dimer [(Me₂N)₂(HNMe₂)Ti(μ₂-N[2,6-Me₂C₆H₃])₂Ti(NHMe₂)(NMe₂)][B(C₆F₅)₄] (2). Protonation of CpTi(NMe₂)₃ and Cp^∗Ti(NMe₂)₃ results in isolation of the salts, [CpTi(NMe₂)₂(NHMe₂)][B(C₆F₅)₄] (3) and [Cp^∗Ti(NMe₂)₂(NHMe₂)][B(C₆F₅)₄] (4), respectively. Treatment of compounds 3 or 4 with H₂N[2,6-ⁱPr₂C₆H₃] results in formation of the imido salts [CpTi(N[2,6-ⁱPr₂C₆H₃])(NHMe₂)₂][B(C₆F₅)₄] (5) (58% yield) or [Cp^∗Ti(N[2,6-ⁱPr₂C₆H₃])(NHMe₂)₂][B(C₆F₅)₄] (6). When Ti(NMe₂)₄ is treated with [Et₃Si][B(C₆F₅)₄], the salt [Ti(NMe₂)₃(N[SiEt₃]Me₂)][B(C₆F₅)₄] (7) is obtained, and treatment of the latter with [2,6-ⁱPr₂C₆H₃]NCHtol produces the imine adduct [Ti(NMe₂)₃(κ¹-[2,6-ⁱPr₂C₆H₃]NCHtol)][B(C₆F₅)₄] (8). The carboamination catalytic activity of complexes 2-7 was investigated and compared to [Ti(NMe₂)₃(NHMe₂)][B(C₆F₅)₄]. Likewise, a proposed mechanism to the active carboamination catalyst stemming from [Ti(NMe₂)₃(NHMe₂)][B(C₆F₅)₄] is described.     

Cp2Ti{[OC(O)C5H4]Cr(CO)2NO]}2 and Cp2Ti{[(OC(O)C5H4]Cr(NO)2X}2 syntheses and spectra of chromium-titanium complexes bridged by carboxylate substituted cyclopentadienyl group

Complete demethylation of Cp₂Ti(CH₃)₂ in dichloromethane with 2 M equivalent of [η⁵-(C₅H₄COOH)]Cr(CO)₂NO (5), [η⁵-(C₅H₄COOH)]Cr(NO)₂X] (X = Cl 6, X = I 7), and [η⁵-(C₅H₄COOH)]W(CO)₃CH₃ (8); gives Cp₂Ti{[OC(O)C₅H₄]Cr(CO)₂NO}₂ (13), Cp₂Ti{[OC(O)C₅H₄]Cr(NO)₂Cl}₂ (14), Cp₂Ti{[OC(O)C₅H₄]Cr(NO)₂I}₂ (15),and Cp₂Ti{[OC(O)C₅H₄]W(CO)₃CH₃}₂ (16), respectively. The chemical shifts of C(2)-C(5) carbon atoms of compounds 13-15 have been assigned using two-dimensional HetCOR NMR spectroscopy. The assigned chemical shifts were compared with the NMR data of their analogues of ferrocene, and the opposite correlation on the assignments was observed for cynichrodenoyl moieties.     

Synthesis,crystal structure and magnetic properties of the helical oxalate-bridged copper(II) chain {[(CH3)4N]2[Cu(C2O4)2] · H2O}n

The preparation, crystal structure and magnetic properties of a new oxalate-containing copper(II) chain of formula {[(CH₃)₄N]₂[Cu(C₂O₄)₂] · H₂O}_n (1) [(CH₃)₄N⁺ = tetramethylammonium cation] are reported. The structure of 1 consists of anionic oxalate-bridged copper(II) chains, tetramethylammoniun cations and crystallization water molecules. Each copper(II) ion in 1 is surrounded by three oxalate ligands, one being bidentate and the other two exhibiting bis-bidenate coordination modes. Although all the tris-chelated copper(II) units from a given chain exhibit the same helicity, adjacent chains have opposite helicities and then an achiral structure results. Variable-temperature magnetic susceptibility measurements of 1 show the occurrence of a weak ferromagnetic interaction through the oxalate bridge [J = +1.14(1) cm⁻¹, the Hamiltonian being defined as H = –J ∑_nmS_i · S_j]. This value is analyzed and discussed in the light of available magneto-structural data for oxalate-bridged copper(II) complexes with the same out-of-plane exchange pathway.     

Synthesis, structural characterization, and magnetic properties of the metallamacrocycle [Fe6(C11H11N2O3)6(C4H9NO)6]

Abstract  

The 18-metallacrown-6 metallamacrocycle [Fe₆(pmshz)₆(C₄H₉NO)₆] has been synthesized by the self-assembly reaction of iron ions with N-substituted salicylhydrazide ligands. Six Fe(III) ions and six deprotonated N-propanoyl-4-methylsalicylhydrazide (H₃ pmshz) ligands construct a planar 18-membered ring based on Fe–N–N–Fe linkage. Because of the coordination, the ligand enforces the stereochemistry of the Fe(III) ions as a propeller shape with alternating …ΔΛΔΛ… configurations. There is a strong antiferromagnetic exchange interaction between the paramagnetic iron centers.     

Synthesis and study of (CN3H6)2[(UO2)2(C2O4)(SeO3)2] by IR spectroscopy and X-ray diffraction

Single crystals of (CN₃H₆)₂[(UO₂)₂(C₂O₄)(SeO₃)₂] were synthesized and studied by IR spectroscopy and X-ray diffraction. The compound crystallizes in the triclinic system with the unit cell parameters a = 7.1169(12) ?, b = 7.4874(10) ?, c = 8.9748(14) ?, α = 88.243(6)°, β = 74.546(6)°, γ = 81.445(6)°, space group P[`1]P\bar 1, Z = 1, R = 0.0304. The main structural units of the crystals are layers of the [(UO₂)₂(C₂O₄)(SeO₃)₂]²⁻ composition; the layers belong to the crystal chemical group A ₂ K ⁰² T ₂³ (A = UO₂²⁺ K ⁰² = C₂O₄²⁻, T ³ = SeO₃^–) of uranyl complexes. Uranium-containing complex groups are linked by electrostatic interactions and a network of hydrogen bonds with CN₃H₆⁺ guanidinium ions to form a three-dimensional framework.     

Synthesis and structural characterization of two cobalt phosphites: 1-D (H3NC6H4NH3)Co(HPO3)2 and 2-D (NH4)2Co2(HPo3)3

Two new cobalt phosphites, (H₃NC₆H₄NH₃)Co(HPO₃)₂ (1) and (NH₄)₂Co₂(HPO₃)₃ (2), have been synthesized and characterized by single-crystal X-ray diffraction. All the cobalt atoms of 1 are in tetrahedral CoO₄ coordination. The structure of 1 comprises twisted square chains of four-rings, which contain alternating vertex-shared CoO₄ tetrahedra and HPO₃ groups. These chains are interlinked with trans-1,4-diaminocyclohexane cations by hydrogen bonds. The 2-D structure of 2 comprises anionic complex sheets with ammonium cations present between them. An anionic complex sheet contains three-deck phosphite units, which are interconnected by Co₂O₉ to form complex layers. Magnetic susceptibility measurements of 1 and 2 showed that they have a weak antiferromagnetic interaction.     

X-Ray Diffraction Study of Cs5(HSO4)3(H2PO4)2, a New Solid Acid with a Unique Hydrogen-Bond Network

Solid solution investigations in the CsHSO₄–CsH₂PO₄system, carried out as part of an ongoing effort to elucidate the relationship between proton conduction, hydrogen bonding, and phase transitions, yielded the new compound Cs₅(HSO₄)₃(H₂PO₄)₂. Single-crystal X-ray diffraction methods revealed that Cs₅(HSO₄)₃(H₂PO₄)₂crystallizes in space groupC2/c(or possiblyCc), has lattice parametersa=34.066(19) Å,b=7.661(4) Å,c=9.158(6) Å, andβ=90.44(6)°, a unit cell volume of 2389.9(24) ų, a density of 3.198 Mg m⁻³, and four formula units in the unit cell. Sixteen non-hydrogen atoms and five hydrogen sites were located in the asymmetric unit, the latter on the basis of geometric considerations rather than from Fourier difference maps. Refinement using anisotropic temperature factors for all non-hydrogen atoms and fixed isotropic temperature factors for all hydrogen atoms yielded residuals based onF²(weighted) andFvalues, respectively, of 0.0767 and 0.0340 for observed reflections [F²>2σ(F²)]. The structure contains layers of (CsH₂XO₄)₂that alternate with layers of (CsHXO₄)₃, whereXis P or S. The arrangement of Cs, H, andXO₄groups within the two types of layers is almost identical to that in the end-member compounds, CsH₂PO₄and CsHSO₄-II, respectively. Although P and S each reside on two of the threeXatom sites in Cs₅(HSO₄)₃(H₂PO₄)₂, the number of protons in the structure appears fixed. In addition, the correlation of S–O and S–OH bond distances with O···O distances, where the latter represents the distance between two hydrogen-bonded oxygen atoms, was determined from a review of literature data.     

Supramolecular aggregation in new crystals with nonlinear optical properties: 2-aminophenol-HClO4, 3-aminophenol-HClO4 and 4-aminophenol-HClO4

Three new hybrid crystals of 2-aminophenol-HClO₄ (2-AP-HClO₄, 1), 3-aminophenol-HClO₄ (3-AP-HClO₄, 2) and 4-aminophenol-HClO₄ (4-AP-HClO₄, 3) were obtained and their crystal structures determined. The 1 crystallises in centrosymmetric space group C2/c of monoclinic system while the other two (2 and 3) crystallise in the non-centro symmetric space group P2₁ and P2₁2₁2₁, respectively. The oppositely charged units of the crystals, i.e. positively charged 2-APH⁺, 3-APH⁺ and 4-APH⁺ and ClO₄⁻, interact via weak N⁺–HO and O–HO hydrogen bonds forming 3D-supramolecular network. Relative to KDP the SHG efficiencies are 0.62 for 2 and 0.33 for 3, measured at 1064 nm using the Kurtz–Perry method.     

Syntheses, crystal structures and spectroscopic properties of KEu[AsS4], K3Dy[AsS4]2 and Rb4Nd0.67[AsS4]2

Three rare earth compounds, KEu[AsS₄] (1), K₃Dy[AsS₄]₂ (2), and Rb₄Nd_0.67[AsS₄]₂ (3) have been synthesized employing the molten flux method. The reactions of A₂S₃ (A = K, Rb), Ln (Ln = Eu, Dy, Nd), As₂S₃, S were accomplished at 600 °C for 96 h in evacuated fused silica ampoules. Crystal data for these compounds are: 1, monoclinic, space group P2₁/m (no. 11), a = 6.7276(7) Å, b = 6.7190(5) Å, c = 8.6947(9) Å, β = 107.287(12)°, Z = 2; 2, monoclinic, space group C2/c (no. 15), a = 10.3381(7) Å, b = 18.7439(12) Å, c = 8.8185(6) Å, β = 117.060(7)°, Z = 4; 3, orthorhombic, space group Ibam (no. 72), a = 18.7333(15) Å, b = 9.1461(5) Å, c = 10.2060(6) Å, Z = 4. 1 is a two-dimensional structure with ²_∞[Eu(AsS₄)]⁻ layers separated by potassium cations. Within each layer, distorted bicapped trigonal [EuS₈] prisms are linked through distorted [AsS₄]³⁻ tetrahedra. Each Eu²⁺ cation is coordinated by two [AsS₄]³⁻ units by edge-sharing and bonded to further two [AsS₄]³⁻ units by corner-sharing. Compound 2 contains a one-dimensional structure with ¹_∞[Dy(AsS₄)₂]³⁻ chains separated by potassium cations. Within each chain, distorted bicapped trigonal prisms of [DyS₈] are linked by slightly distorted [AsS₄]³⁻ tetrahedra. Each Dy³⁺ ion is surrounded by four [AsS₄]³⁻ moieties in an edge-sharing fashion. For compound 3 also a one-dimensional structure with ¹_∞[Nd₀.₆₇(AsS₄)₂]⁴⁻ chains is observed. But the Nd position is only partially occupied and overall every third Nd atom is missing along the chain. This cuts the infinite chains into short dimers containing two bridging [As₄]³⁻ units and four terminal [AsS₄]³⁻ groups. 1 is characterized with UV/vis diffuse reflectance spectroscopy, IR, and Raman spectra.     

Group 12 metal aryl selenolates. Crystal and molecular structure of [2-(Et2NCH2)C6H4]2Se2 and [2-(Me2NCH2)C6H4Se]2M (M = Zn, Cd)

Diorganodiselenide [2-(Et₂NCH₂)C₆H₄]₂Se₂ (1) was obtained by hydrolysis/oxidation of the corresponding [2-(Et₂NCH₂)C₆H₄]SeLi derivative. The treatment of [2-(Et₂NCH₂)C₆H₄]₂Se₂ with elemental sodium in THF resulted in [2-(Et₂NCH₂)C₆H₄]SeNa (2). Reactions between alkali metal selenolates [2-(R₂NCH₂)C₆H₄]SeM′ (R = Me, Et; M′ = Li, Na) and MCl₂ (M = Zn, Cd) in a 2:1 molar ratio resulted in the [2-(R₂NCH₂)C₆H₄Se]₂M species [R = Me, M = Zn (3), Cd (4); R = Et, M = Zn (5), Cd (6)]. The new compounds were characterized by multinuclear NMR (¹H, ¹³C, ⁷⁷Se, ¹¹³Cd) and mass spectrometry. The crystal and molecular structures of 1, 3 and 4 revealed monomeric species stabilized by N → Se (for 1) and N → M (for 3 and 4) intramolecular interactions.