(5Z)‐4‐Amino‐2‐(4‐hydroxyphenyl)‐1H‐imidazol‐5(2H)‐one oxime 3‐oxide

The title molecule, C₉H₁₀N₄O₃, consists of benzene and imidazole rings which are almost perpendicular to each other. A hydroxyimino group is directly linked to the imidazole ring with a double C=N bond, which is the first example in this type of compound. The double bond may be a good location for the initiation of various reactions with a wide range of potential applications. In the crystal structure, there are π–π interactions between molecules related by a centre of symmetry, with the imidazole and benzene rings almost completely overlapped. The molecules are hydrogen bonded in each direction and form a three‐dimensional hydrogen‐bond network.     

(Z)‐5‐[4‐(Dimethylamino)benzylidene]‐2‐(piperidin‐1‐yl)‐1,3‐thiazolidin‐4(5H)‐one

The molecules of the title compound, C₁₇H₂₁N₃OS, are characterized by a wide C—C—C angle at the methine C atom linking the aryl and thiazolidine rings, associated with a short repulsive intramolecular S...H contact between atoms in these two rings. A single piperidine–arene C—H...π hydrogen bond links pairs of molecules into centrosymmetric dimers.     

Two isomorphous azastilbene derivatives: 1‐(2‐chlorobenzyl)‐4‐[(E)‐2‐(4‐hydroxyphenyl)ethenyl]pyridinium chloride and 1‐(2‐bromobenzyl)‐4‐[(E)‐2‐(4‐hydroxyphenyl)ethenyl]pyridinium bromide

The crystal structures of the two title (E)‐stilbazolium halogenates, C₂₀H₁₇ClNO⁺·Cl⁻ and C₂₀H₁₇BrNO⁺·Br⁻, are isomorphous, with an isostructurality index of 0.985. The azastyryl fragments are almost planar, with dihedral angles between the benzene and pyridine rings of ca 4.5°. The rings of the benzyl groups are, in turn, almost perpendicular to the azastyryl planes, with dihedral angles larger than 80°. The cations and anions are connected by O—H...X⁻ (X = halogen) hydrogen bonds. The halide anions are `sandwiched' between the charged pyridinium rings of neighbouring molecules, and weak C—H...O hydrogen bonds and C—H...X and C—H...π interactions also contribute to the crystal structures.     

[2‐(2‐{Bis[2‐(1H‐imidazol‐2‐ylmethyleneamino)ethyl]amino}ethyliminomethyl)imidazolido]cobalt(III) bis(tetrafluoridoborate) monohydrate

The title compound, [Co(C₁₈H₂₃N₁₀)](BF₄)₂·H₂O, is the result of complexing a Co cation (initially in a Co^II state) with tris[2‐(1H‐imidazol‐2‐ylmethyleneamino)ethyl]amine (L), obtained by a condensation process involving imidazole‐2‐carbaldehyde and tris(2‐aminoethyl)amine. Both the Co cation and the ligand were modified in the synthesis process, the cation via oxidation to Co^III, and the ligand via deprotonation to convert it into the 2‐(2‐{bis[2‐(1H‐imidazol‐2‐ylmethyleneamino)ethyl]amino}ethyliminomethyl)imidazolide anion (L⁻). The ligand chelates the metal centre in a hexadentate fashion, forming a slightly distorted octahedral CoN₆ chromophore. Packing is governed by N—H...N hydrogen bonds defining zigzag chains. A similar structure in the literature is discussed, and the wrong assignment of the oxidation state, given therein to the Co cation, is corrected.     

Conformational study of (Z)‐5‐(4‐chlorobenzylidene)‐2‐[4‐(2‐hydroxyethyl)piperazin‐1‐yl]‐3H‐imidazol‐4(5H)‐one in different environments: insight into the structural properties of bacterial efflux pump inhibitors

The 2‐amine derivatives of 5‐arylidene‐3H‐imidazol‐4(5H )‐one are a new class of bacterial efflux pump inhibitors, the chemical compounds that are able to restore antibiotic efficacy against multidrug resistant bacteria. 5‐Arylidene‐3H‐imidazol‐4(5H )‐ones with a piperazine ring at position 2 reverse the mechanisms of multidrug resistance (MDR) of the particularly dangerous Gram‐negative bacteria E. coli by inhibition of the efflux pump AcrA/AcrB/TolC (a main multidrug resistance mechanism in Gram‐negative bacteria, consisting of a membrane fusion protein, AcrA, a Resistant‐Nodulation‐Division protein, AcrB, and an outer membrane factor, TolC). In order to study the influence of the environment on the conformation of (Z )‐5‐(4‐chlorobenzylidene)‐2‐[4‐(2‐hydroxyethyl)piperazin‐1‐yl]‐3H‐imidazol‐4(5H )‐one, ( 3 ), two different salts were prepared, namely with picolinic acid {systematic name: 4‐[(Z )‐4‐(4‐chlorobenzylidene)‐5‐oxo‐3,4‐dihydro‐1H‐imidazol‐2‐yl]‐1‐(2‐hydroxyethyl)piperazin‐1‐ium pyridine‐2‐carboxylate, C₁₆H₂₀ClN₄O₂⁺·C₆H₄NO₂⁻, ( 3 a )} and 4‐nitrophenylacetic acid {systematic name: 4‐[(Z )‐4‐(4‐chlorobenzylidene)‐5‐oxo‐3,4‐dihydro‐1H‐imidazol‐2‐yl]‐1‐(2‐hydroxyethyl)piperazin‐1‐ium 2‐(4‐nitrophenyl)acetate, C₁₆H₂₀ClN₄O₂⁺·C₈H₆NO₄⁻, ( 3 b )}. The crystal structures of the new salts were determined by X‐ray diffraction. In both crystal structures, the molecule of ( 3 ) is protonated at an N atom of the piperazine ring by proton transfer from the corresponding acid. The carboxylate group of picolinate engages in hydrogen bonds with three molecules of the cation of ( 3 ), whereas the carboxylate group of 4‐nitrophenylacetate engages in hydrogen bonds with only two molecules of ( 3 ). As a consequence of these interactions, different orientations of the hydroxyethyl group of ( 3 ) are observed. The crystal structures are additionally stabilized by both C—H…N [in ( 3 a )] and C—H…O [in ( 3 a ) and ( 3 b )] intermolecular interactions. The geometry of the imidazolone fragment was compared with other crystal structures possessing this moiety. The tautomer observed in the crystal structures presented here, namely 3H‐imidazol‐4(5H )‐one [systematic name: 1H‐imidazol‐5(4H )‐one], is also that most frequently observed in other structures containing this heterocycle.     

6‐(2‐Fluorobenzylidene)‐2‐[1‐(2‐fluoro‐4‐biphenyl)ethyl]thiazolo[3,2‐b][1,2,4]triazol‐5(6H)‐one

The title compound, C₂₅H₁₇F₂N₃OS, was synthesized from 6‐(benzyl­idene)­thia­zolo­[3,2‐b][1,2,4]triazol‐5(6H)‐one. The fused thia­zolo­[3,2‐b][1,2,4]triazole system is essentially planar, and bifurcated C—H⋯O, C—H⋯N and C—H⋯F interactions are present between mol­ecules.     

6‐[(4‐Fluorophenyl)(1H‐imidazol‐1‐yl)methyl]‐1,3‐benzodioxol‐5‐ol and 6‐[(4‐methoxyphenyl)(1H‐imidazol‐1‐yl)methyl]‐1,3‐benzodioxol‐5‐ol

The title compounds, C₁₇H₁₃FN₂O₃ and C₁₈H₁₆N₂O₄, are new potent aromatase inhibitors combining the common features of second‐ and third‐generation nonsteroid anti‐aromatase compounds. The molecules have a propeller shape, with dihedral angles between adjacent planes in the range 49–86°. A quantum mechanical ab initio Roothaan–Hartree–Fock calculation for the isolated molecules shows values for these angles close to the ideal value of 90°. Docking studies of the molecules in the aromatase substrate show that their strong inhibitor potency can be attributed to molecular flexibility, hydrophobic interactions, heme Fe coordination and hydrogen bonding.     

NMR studies on 1,2‐dihydro‐2‐(4‐aminophenyl)‐4‐[4‐(4‐aminophenoxy)‐4‐phenyl]‐(2H)phthalazin‐1‐one

An unsymmetrical heterocyclic diamine, 1,2‐dihydro‐2‐(4‐aminophenyl)‐4‐[4‐(4‐aminophenoxy)‐4‐phenyl]‐(2H)phthalazin‐1‐one, was synthesized. Its ¹H and ¹³C NMR spectra were completely assigned by utilizing the two‐dimensional heteronuclear ¹³C–¹H multiple‐bond coherence (HMBC) spectroscopy, and heteronuclear ¹³C–¹H one‐bond correlation spectroscopy, homonuclear shift correlation spectroscopy (H,H‐COSY) and rotating frame Overhauser enhancement spectroscopy (ROESY). The structure of the compound was shown to be the phthalazinone rather than the phthalazine ether from cross peaks and chemical shifts of the protons. Copyright © 2002 John Wiley & Sons, Ltd.     

4,6‐Dimethyl‐2‐[(4‐phenylpiperidin‐1‐yl)methyl]isothiazolo[5,4‐b]pyridin‐3(2H)‐one and 4,6‐dimethyl‐2‐[(4‐phenyl‐1,2,3,6‐tetrahydropyridin‐1‐yl)methyl]isothiazolo[5,4‐b]pyridin‐3(2H)‐one

In the crystal structures of the title compounds, C₂₀H₂₃N₃OS, (II), and C₂₀H₂₁N₃OS, (III), significant differences occur in the conformation of, respectively, the phenylpiperidine and phenyltetrahydropyridine substituents at the 2‐position of the isothiazolopyridine system. The piperidine ring adopts a chair conformation, while the tetrahydropyridine ring assumes a half‐chair form. The phenylpiperidine and phenyltetrahydropyridine fragments exhibit different conformations resulting from the steric and conjugation effects in the phenyl ring, respectively. Theoretical calculations show that both conformations are energetically stable and correspond to a minimum of energy for the analyzed systems. The molecular packing in (II) is influenced by π–π interactions of the isothiazolopyridine systems, with a shortest centroid‐to‐centroid separation of 3.5843 (11) Å between pyridine rings. In the crystal structure of (III), the molecules are linked by C—H...O hydrogen bonds and C—H...π interactions.     

1‐[(4‐Chloro­benzoyl)­methyl]‐4‐(N,N‐di­methyl­amino)­pyridinium bromide sesquihydrate and 1‐[(4‐bromo­benzoyl)­methyl]‐4‐(N,N‐di­methyl­amino)­pyridinium bromide sesquihydrate

The title compounds, C₁₅H₁₆ClN₂O⁺·Br⁻·1.5H₂O and C₁₅H₁₆BrN₂O⁺·Br⁻·1.5H₂O, are isomorphous. The benzene ring is oriented nearly normal to the pyridine ring in both compounds. The molecular packing is mainly influenced by intermolecular O—H⋯O and O—H⋯Br interactions, as well as weak intramolecular C—H⋯O interactions. The H₂OBr⁻ units form an extended water–bromide chain, with a bridging water mol­ecule on a twofold axis.     

(Z)‐5‐[(5‐Methyl‐1H‐imidazol‐4‐yl)methylidene]‐2‐sulfanylidene‐1,3‐thiazolidin‐4‐one monohydrate: a three‐dimensional hydrogen‐bonded framework structure

The non‐H atoms in the organic component of the title compound, C₈H₇N₃OS₂·H₂O, are almost coplanar, as the dihedral angle between the two ring planes is only 1.8 (2)°; there is a wide C—C—C angle of 127.8 (3)° at the methine C atom linking the two rings. The molecular components are linked into a three‐dimensional framework structure by two‐centre hydrogen bonds of N—H...O and O—H...N types, together with a three‐centre O—H...(N,S) system. Comparisons are made with some (Z)‐5‐arylmethylidene‐2‐sulfanylidene‐1,3‐thiazolidin‐4‐ones.     

[2‐(Imidazol‐4‐yl)ethylamine]{[2‐(imidazol‐4‐yl)ethyl][(1‐methylimidazol‐2‐yl)methyl]amine}copper(II) diperchlorate

In the title mononuclear complex, [Cu(C₅H₉N₃)(C₁₀H₁₅N₅)](ClO₄)₂, the Cu^II centre is surrounded by two N‐donor ligands, which impose a square‐pyramidal environment on the metal. The new tridentate ligand [2‐(imidazol‐4‐yl)­ethyl]­[(1‐methyl­imidazol‐2‐yl)­methyl]­amine (HISMIMA) lies in the basal plane, while the hist­amine ligand occupies the apical and one of the basal positions around the Cu^II ion.     

3,5‐Dimethyl‐4‐[(E)‐(2‐nitrophenyl)diazenyl]‐1‐(2,3,4,5,6‐pentafluorophenyl)‐1H‐pyrazole

The title compound, C₁₇H₁₀F₅N₅O₂, is described and compared with its 4‐nitrophenyl isomer [Bustos, Sánchez, Schott, Alvarez‐Thon & Fuentealba (2007). Acta Cryst. E 63 , o1138–o1139]. The title molecule presents its nitro group split into two rotationally disordered components, which in conjunction with the rotation of the `unclamped' rings constitute the main molecular differences. Packing is directed by a head‐to‐tail type `I' C—F...F—C interaction, generating double‐chain strips running along [100]. These substructures are interlinked by a variety of weak F...F, O...F, F...π and O...π interactions.     

2‐[(E)‐(4‐Hydroxy‐3‐methoxybenzylidene)amino]‐N‐(2‐methylphenyl)‐4,5,6,7‐tetrahydro‐1‐benzothiophene‐3‐carboxamide

The title compound, C₂₄H₂₄N₂O₃S, exhibits antifungal and antibacterial properties. The compound crystallizes with two molecules in the asymmetric unit, with one molecule exhibiting `orientational disorder' in the crystal structure with respect to the cyclohexene ring. The o‐toluidine groups in both molecules are noncoplanar with the respective cyclohexene‐fused thiophene ring. In both molecules, there is an intramolecular N—H...N hydrogen bond forming a pseudo‐six‐membered ring which locks the molecular conformation and eliminates conformational flexibility. The crystal structure is stabilized by O—H...O hydrogen bonds; both molecules in the asymmetric unit form independent chains, each such chain consisting of alternating `ordered' and `disordered' molecules in the crystal lattice.     

The cocrystal rac‐1‐[(N,4‐dimethylbenzenesulfonamido)methyl]‐2‐(diphenylphosphoryl)ferrocene–rac‐1‐[(N,4‐dimethylbenzenesulfonamido)methyl]‐2‐(diphenylphosphanyl)ferrocene (0.45/0.55)

As part of our interest in the synthesis and catalytic applications of chiral (diphenylphosphanyl)ferrocene ligands, we designed a number of P,N‐containing ligands for use in asymmetric transfer hydrogenation (ATH). During the synthetic procedure to obtain rac‐1‐[(N,4‐dimethylbenzenesulfonamido)methyl]‐2‐(diphenylphosphanyl)ferrocene, the title compound, [Fe(C₅H₅)(C₂₆H₂₅NO₂PS)]_0.55·[Fe(C₅H₅)(C₂₆H₂₅NO₃PS)]_0.45, was obtained as a by‐product. It is composed of a ferrocene group disubstituted by a partially oxidized diphenylphosphanyl group, as confirmed by ³¹P NMR analysis, and an (N,4‐dimethylbenzenesulfonamido)methyl substituent. Owing to the partially oxidized diphenylphosphanyl group, it is best to view the crystal as being composed of a mixture of non‐oxidized and oxidized phosphane, so it can be regarded as a cocrystal. It is also a racemate. To the best of our knowledge, the P=O distance [1.344 (4) Å] is the shortest observed for related (diphenylphosphoryl)ferrocene compounds. The packing is stabilized by weak C—H...O interactions, forming R₂²(10) hydrogen‐bonding motifs, which build up a chain along the c axis.     

(3R,4S)‐3‐Phenyl‐1‐[(R)‐1‐phenyl­ethyl]‐4‐[(R)‐1‐phenylethyliminomethyl]azetidin‐2‐one

The configuration of the chiral ring atoms of the title compound, C₂₆H₂₆N₂O, obtained in an enantioselective synthesis, has been established relative to the known R configuration of the α‐methyl­benzyl moieties. The crystal packing involves a two‐dimensional network of C—H?π interactions between the aromatic rings.     

An oxazol‐5(4H)‐one from benzyloxy­carbonyl‐(Aib)4‐OH

Benzyl N‐[8‐(4,4‐dimethyl‐5‐oxo‐4,5‐dihydrooxazol‐2‐yl)‐2,5,5,8‐tetra­methyl‐3,6‐dioxo‐4,7‐diazanon‐2‐yl]­carbamate, C₂₄H₃₄N₄O₆, an oxazol‐5(4H)‐one from N‐α‐benzyloxycarbonyl‐(Aib)₄‐OH (Aib = α‐amino­isobutyryl) represents the longest peptide oxazolone so far characterized by X‐ray diffraction. The overall geometry of the oxazolone ring compares well with literature data. The Aib(1) and Aib(2) residues are folded into a type III β‐bend, while the conformation adopted by Aib(3), preceding the oxazolone moiety, is semi‐extended. The disposition of the oxazolone ring relative to the preceding residue is stabilized by C—­H?N and C—H?O intramolecular interactions.     

3‐[4‐(4‐Fluoro­phenyl)­piperazin‐1‐yl­methyl]‐5‐methyl‐1,3‐benzoxazol‐2(3H)‐one and 3‐[4‐(2‐fluoro­phenyl)­piperazin‐1‐yl­methyl]‐5‐methyl‐1,3‐benzoxazol‐2(3H)‐one

The title compounds, both C₁₉H₂₀FN₃O₂, contain essentially planar benzoxazolinone ring systems, within which the C—N bond distances and angles do not differ significantly between the two compounds. In both cases, the piperazine ring adopts an almost perfect chair conformation and the benzoxazo­l­inone ring system lies nearly perpendicular to it. The structures contain intermolecular C—H⋯O contacts, and the interactions between the benzoxazolinone and fluoro­phenyl­piperazine portions of the mol­ecules are segregated.     

Cocrystallization of two tautomers: 4‐(1‐{[4‐(dimethylamino)benzylidene]hydrazono}ethyl)benzene‐1,3‐diol and 6‐[(E)‐1‐{[4‐(dimethylamino)benzylidene]hydrazino}ethylidene]‐3‐hydroxycyclohexa‐2,4‐dien‐1‐one (1/1)

Two different tautomeric forms of a new Schiff base, C₁₇H₁₉N₃O₂·C₁₇H₁₉N₃O₂, are present in the crystal in a 1:1 ratio, namely the enol–imine form 4‐(1‐{[4‐(dimethylamino)benzylidene]hydrazono}ethyl)benzene‐1,3‐diol and the keto–amine form 6‐[(E)‐1‐{[4‐(dimethylamino)benzylidene]hydrazino}ethylidene]‐3‐hydroxycyclohexa‐2,4‐dien‐1‐one. The tautomers are formed by proton transfer between the hydroxy O atom and the imine N atom and are hydrogen bonded to each other to form a one‐dimensional zigzag chain along the crystallographic b axis via intermolecular hydrogen bonds.     

2‐Amino‐5‐(3,4‐dimethoxybenzylidene)‐1‐methylimidazol‐4(5H)‐one N,N‐dimethylformamide monosolvate

The crystal structure of the title compound, C₁₃H₁₅N₃O₃·C₃H₇NO, was determined as part of a larger project focusing on creatinine derivatives as potential pharmaceuticals. The molecule is essentially planar, in part because of intramolecular hydrogen bonding. Inversion‐related pairs of molecules result from intermolecular hydrogen bonding. The π systems of 2‐amino‐5‐(3,4‐dimethoxybenzylidene)‐1‐methylimidazol‐4(5H)‐one and an inversion‐related molecule overlap slightly, indicating a small amount of π–π stacking. Bond lengths, angles and torsion angles are consistent with similar structures, except in the imidazolone ring near the doubly bonded C atom, where significant differences occur.