Darzens reaction as a convenient method for the synthesis of α-chloroketones, α-chloroepoxides,and symmetrically substituted dioxines

Summary TheDarzens reaction of dichloroacetophenone (DCAP) with substituted benzaldehydes has been studied. The structure of the products was shown to depend on the phenyl group substituents. Reaction of benzaldehyde, 4-bromo-, and 2,4-dichlorobenzaldehydes results in 1-phenyl-3-aryl-3-chloropropane-1,2-diones (2a–c), reaction ofpara- ormeta-nitrobenzaldehydes yields 1-phenyl-2-chloro-3-aryl-2,3-epoxypropane-1-ones (3a, b). Upon the introduction of an alkoxy group into the phenyl ring of benzaldexyde and/or dichloroacetophenone, symmetrically substituted dioxines were obtained (6a–c). The structure of the reaction products has been established by single crystal X-ray investigations.

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Darzens-Reaktion als bequemes Verfahren zur Synthese von -Chloroketonen, -Chloroepoxiden und symmetrisch substituierten Dioxinen

Zusammenfassung DieDarzens-Reaction von Dichloracetophenon (DCAP) mit substituierten Benzaldehyden wurde untersucht. Die Struktur der Produkte ist von den Substituenten an der Phenylgruppe abhängig. Die Umsetzung mit Benzaldehyd, 4-Brom- und 2,4-Dichlorbenzaldehyd liefert 1-Phenyl-3-aryl-3-chloropropan-1,2-dione (2a–c), die Reaktion vonpara- odermeta-Nitrobenzaldehyd 1-Phenyl-2-chloro-3-aryl-2,3-epoxipropan-1-one (3a,b). Durch Einführung einer Alkoxygruppe in den Phenylring des Benzaldehyds und/oder des Dichloracetophenons erhält man symmetrisch substituierte Dioxine (6a–c). Die Struktur der Reaktionsprodukte wurde mittels Röntgenstrukturanalyse bestätigt.

     

Trifluoroethanol as a metal-free, homogeneous and recyclable medium for the efficient one-pot synthesis of α-amino nitriles and α-amino phosphonates

Trifluoroethanol is found to be an efficient and recyclable medium in promoting one-pot, three-component coupling reactions of aldehydes or ketones, amines and trimethylsilyl cyanide or trimethyl phosphite to afford the corresponding α-amino nitriles or α-amino phosphonates in high yields. This protocol does not require the use of an acid or base catalyst.     

Synthesis and Crystal Structure of a Novel Ethyl 5-（4-（2-Phenylacetamido）phenyl）-lH-pyrazole- 3-carboxylate as an Acrosin Inhibitor

The title compound （ethyl5-（4-（2-phenylacetamido）phenyl）-lH-pyrazole-3-carboxylate, C20H19N3O3） was synthesized by the reaction of Claisen condensation, cyclization, reduction and acylation. The struct...     

Synthesis,Crystal Structure and Thermal Behavior of a New 2D Barium（Ⅱ） Coordination Polymer with 1H-benzimi-dazole-5,6-dicarboxylate as the Single Ligand

The self-assembly of 1H-benzimidazole-5,6-dicarboxylic acid with barium chloride under hydrothermal conditions afforded a new 2D coordination polymer,[Ba2(L)(HL)Cl]n(1,L = 1H-benzimidazole-5,6-dicarboxylate),which was characterized by elemental analysis,infrared spectroscopy,thermogravimetric analysis,and single-crystal X-ray diffraction.Compound 1 is of monoclinic system,space group P21/c with a = 10.0145(6),b=25.6854(15),c=7.3116(4) ?,β = 99.4980(10)°,V = 1854.95(19)3,C18H9Ba2ClN4O8,Z = 4,Mr=719.42,Dc = 2.576 g/cm3,μ(MoKα) = 4.427 mm-1,F(000) = 1352,the final R = 0.0202 and wR=0.0465 for 3051 observed reflections with I > 2σ(I).It exhibits an interesting two-dimensional network structure and high thermal stability(up to 420 ℃).     

Fabrication and characterization of a α,β,γ,δ-Tetrakis(1-methylpyridinium-4-yl)porphine/silica nanocomposite thin-layer membrane for detection of ppb-level heavy metal ions

A new detection membrane for filtration enrichment combined with colorimetric determination of Cd(II), Zn(II), Pb(II) and Cu(II) ions is presented. We have demonstrated the use of a dye nanoparticle coated test strip (DNTS) structured with a reagent layer for on-site analysis of trace metal ions. In this study, a [TMPyP/SA] DNTS coated with a nanocomposite layer (average thickness: 5.39 μm) of α,β,γ,δ-Tetrakis(1-methylpyridinium-4-yl)porphine (TMPyP) and silica-SA on the top surface of a cellulose ester membrane filter was fabricated by a simple filtration of an aqueous TMPyP/silica-SA nanocomposite dispersion through a membrane filter. The nanocomposite formation of cationic TMPyP and negatively charged colloidal SA (9–80 nm) was based on electrostatic interaction and was confirmed in the 120–800 nm diameter range by a dynamic light scattering photometer (DLS). To optimize the DNTS nanocomposite layer, surface uniformity, mechanical strength, the percent retention of TMPyP, and sensitivity to Cd(II) detection for six DNTSs with five different types of silica were examined. A half[TMPyP/SA] DNTS with an average layer thickness of 2.60 μm, which was prepared by controlling the amount of TMPyP and SA, demonstrated the highest sensitivity to Cd(II) ion because it had the lowest background absorbance. In addition, factors that affected the percent retention of TMPyP, such as pH and TMPyP/SA ratio, were determined. More than 99% of the TMPyP was retained on a membrane filter at pH 7.8 with a TMPyP and SA concentration of 2 × 10⁻⁵ M and 4 × 10⁻⁵ wt%, respectively. Filtration enrichment of 100 mL of an aqueous solution containing Cd(II), Zn(II), and Pb(II) at ppb levels was achieved by concentrating the metal ions in a nanocomposite layer (the effective TMPyP area was 1.77 cm², pH 10.2). The signaling surface changed from a brown color to green when the ions were captured. The percent extraction for metal ions on a half[TMPyP/SA] DNTS were estimated by TLC scanning and ICP-MS. It was observed that, when using the half[TMPyP/SA] DNTS, Cd(II) concentrations as low as 1 ppb were detectable at a filtration rate of 4.0–5.0 mL min⁻¹.     

Application of dispersive liquid–liquid microextraction with alcoholic solvents followed by HPLC–UV as a sensitive and efficient method for the extraction and determination of citalopram in biological samples using an experimental design

A sensitive and rapid method based on alcoholic-assisted dispersive liquid–liquid microextraction followed by high-performance liquid chromatography for determination of citalopram in human plasma and urine samples was developed. The effects of six parameters (extraction time, stirring speed, pH, volume of extraction and disperser solvents, and ionic strength) on the extraction recovery were investigated and optimized utilizing Plackett–Burman design and Box–Behnken design, respectively. According to Plackett–Burman design results, the volume of disperser solvent, stirring speed, and extraction time had no effect on the recovery of citalopram. The optimized condition was a mixture of 172 µL of 1-octanol as extraction solvent and 400 µL of methanol as disperser solvent, pH of 10.3 and 1% w/v of salt in the sample solution. Replicating the experiment in optimized condition for five times, gave the average extraction recoveries equal to 89.42%. The detection limit of citalopram in human plasma was obtained 4 ng/mL, and the linearity was in the range of 10–1200 ng/mL. The corresponding values for human urine were 5.4 ng/mL with the linearity in the range of 10–2000 ng/mL. Relative standard deviations for inter- and intraday extraction of citalopram were less than 7% for five measurements. The proposed method was successfully implemented for the determination of citalopram in human plasma and urine samples.     

Synthesis, Characterization, and Crystal Structure of a Novel Copper(II) Complex with an Asymmetric Coordinated 2,2'-Bipyridine Derivative: A Model for the Associative Complex in the Ligand-Substitution Reactions of [Cu(tren)L](2+)?

The titled compound, (tris(2-aminoethyl)amine)(4,5-diazafluoren-9-one) copper(II) perchlorate, [Cu(C(6)H(18)N(4))(C(11)H(6)N(2)O)(ClO(4))(2)], 1, has been designed, synthesized, and characterized. The electronic and ESR spectra are very different from those of [Cu(tren)L](2+) complexes where L is monodentate ligand. The X-ray analysis revealed that the complex crystallizes in the monoclinic space group P2(1)/c, with a = 10.726(6) ?, b = 14.921(7) ?, c = 14.649(4) ?, beta = 95.13(3) degrees, and Z = 4. The copper(II) ion is coordinated by four nitrogen atoms from tris(2-aminoethyl)amine (tren) and two nitrogen atoms from 4,5-diazafluoren-9-one (dzf) to form an unusual six-coordinate (4 + 1 + 1') geometry. The structure is very rare, and to our knowledge, it is the first example of an asymmetric bidentate phenanthroline derivative metal complex. The structure could be used as a model of the associative complex in the ligand-exchange and ligand-substitution reactions of [Cu(tren)L](2+) and the catalytic mechanisms of enzymes involving copper sites. From the electronic and variable-temperature ESR spectra in solution, the possible mechanism of these reactions has also been proposed. As a comparison, the complex [Cu(tren)(ImH)(ClO(4))(2)], 2, was also synthesized and characterized, where ImH is imidazole.     

Synthesis and Crystal Structure of the One‐Dimensional Polymer Compound {[Ba(OTf)2(thf)3]2[Ba(OTf)2(thf)2]} (OTf = CF3SO3–) – Excerpts from a Three‐Dimensional Structure as an Access to New Materials?

Ba(CF₃SO₃)₂ reacts with the O‐donor ligand THF to yield the coordination compound {[Ba(OTf)₂(thf)₃]₂[Ba(OTf)₂(thf)₂]} ( 1 ) (OTf = CF₃SO₃^–). The title compound can be described as a one‐dimensional excerpt from the higher‐dimensional crystal structure of Ba(CF₃SO₃)₂, stabilized by THF. This example for the concept of formally “cutting out” structural elements from a three‐dimensional solid state compound confirms and can be compared to the case of the structural “genealogy tree” of BaI₂. This could be an efficient approach for new materials with highly anisotropic properties.     

MM3 Conformational Analysis and X‐ray Crystal Structure of 2,3,4,5‐Tetra‐O‐Acetyl‐N,N′‐Dimethyl‐D‐Glucaramide as a Conformational Model for the d‐Glucaryl Unit of Poly(Alkylene 2,3,4,5‐Tetra‐O‐Acetyl‐d‐Glucaramides)

This report describes the MM3 conformational analysis and X‐ray crystal structure of tetra‐O‐acetyl‐N,N′‐dimethyl‐d‐glucaramide as a conformational model for the D‐glucaryl monomer unit of poly(alkylene tetra‐O‐acyl‐d‐glucaramides). The driving force for this study was to determine the conformational preferences for the diacid unit as a function of the increasing steric bulk of pendant O‐acyl groups: acetyl, propanoyl, 2‐methylpropanoyl, and 2,2‐dimethylpropanoyl. The model dialkyl d‐glucaramides all displayed a large vicinal proton coupling between the central backbone glucaryl hydrogens, indicating an essentially fixed anti conformational arrangement of these protons. The MM3 molecular mechanics program was then applied to calculate the corresponding low‐energy conformations of the structurally simplest of these molecules, tetra‐O‐acetyl‐N,N′‐dimethyl‐d‐glucaramide (4). Given the large number of dihedral angles to be considered and the apparent rigidity of these molecules around the central carbons of the glucaryl backbone, a number of conformational approximations based upon model compounds were applied regarding the rotameric disposition of the pendant O‐acetyl and terminal N‐methyl groups. The calculated, and dominant, lowest energy conformer has a sickle structure very similar to the global minimum conformation previously calculated for unprotected d‐glucaramide. The x‐ray crystal structure data from 4 indicated an extended conformation in the solid state and gave solid‐state torsion angle information that was comparable to that obtained computationally.