The crystal and molecular structures of the diastereomeric (4Z)- and (4E)-3-oxo-2,3-dihydrobilatrienes-abc

The molecular and crystal structures of two diastereomeric 3-oxo-2,3-dihydrobilatrienes-abc1 and2 are determined at low (1, 2) and room temperature (2). The configurations at the exocyclic double bond in position 4 are found to be (Z) for1 and (E) for2. Tautomerism, conformation and crystal packing of1 and2 can be understood on the basis of the pattern of intra- and intermolecular hydrogen bonds. Compared to1, a more open helix conformation is found for the (E) diastereomer2. An analysis of crystallographically observed temperature factors of2 yields the result that the highest flexibility is found for the saturated lactam ring.Herrn Prof.Josef Schurz zum 60. Geburtstag gewidmet.     

1‐[2‐(4‐Nitro­phenoxy)­acetyl]­pyrroli­din‐2‐one: an antiamnesic agent

The title compound, C₁₂H₁₂N₂O₅, is a potential antiamnesic agent. The pyrrolidinone ring has an envelope conformation, and the central moiety is almost coplanar with the planes of the phenyl and pyrrolidinone rings. In the crystal structure, weak intermolecular C—H...O interactions link the mol­ecules into a complex network that can be described by (X) rings (X = 16, 20 and 26) and a C(12) chain.     

Adduct of 2-aminobenzothiazole and 2-hydroxy-3-naphthoic acid and its luminescence properties

The adduct of 2-aminobenzothiazole (1) and 2-hydroxy-3-naphthoic acid (2) is synthesized by the normal temperature volatilization method. The crystal belongs to the monoclinic system, P2₁/c space group. It crystallizes with two independent molecules in the unit, the two independent molecules forming helices through hydrogen bonds. The luminescence property of 1, 2, and the adduct (1·2) were studied at room temperature.     

Synthese und Röntgenkristallstruktur eines (15E)-Dihydrobilatrien-abc-Derivats

The crystal structure of the (15E)-configurated 2,3-dihydrobilatriene-abc2, representing a model compound for the active form of the phytochrome chromophore, was determined at room temperature and at 97 K. Compared to the crystal structure of the corresponding (15Z)-derivative1, the molecule of2 shows a similar helix conformation, but with considerably larger helix pitch. The azide hydrogen atoms are localized at the nitrogen atoms of rings A, C and D. The distribution of bond lengths and bond angles is compatible with previous crystal structures and with the canonical formula. Tautomeric form, conformation and crystal packing are understandable on the basis of the observed intra- and intermolecular hydrogen bonds.

     

Total Synthesis of (−)‐Lundurine A and Determination of its Absolute Configuration

A 15‐step total synthesis of (?)‐lundurine A ( 1 ) from easily accessible (S)‐pyrrolidinone 18 is reported. A Simmons‐Smith reaction allows the efficient, simultaneous assembly of the cyclopropyl C ring, the six‐membered D ring, the seven‐membered E ring, and the quaternary carbon stereocenters at C2 and C7. The absolute configuration of natural (?)‐lundurine A was deduced to be 2R,7R,20R based on the stepwise construction of the stereocenters during the total synthesis.     

Synthesis,characterization, and structures of copper(I) complexes with N,N′-bis[1-(4-chlorophenyl)ethylidene]ethane-1,2-diamine and N,N′-bis[1-(4-nitrophenyl)ethylidene]ethane-1,2-diamine

Two ligands, N,N′-bis[1-(4-chlorophenyl)ethylidene]ethane-1,2-diamine (L¹ ) and N,N′-bis- [1-(4-nitrophenyl)ethylidene]ethane-1,2-diamine (L² ) and their corresponding copper(I) complexes, [Cu(L ¹)₂]ClO₄ (1) and [Cu(L ²)₂]ClO₄ (2), have been synthesized and characterized by CHN analyses, ¹H-NMR, IR, and UV–Vis spectroscopy. The crystal structures of L¹ and [Cu(L ¹)₂]ClO₄ (1) were determined from single crystal X-ray diffraction. L¹ lies across a crystallographic inversion center and the C=N is approximately coplanar with the benzene ring and adopts E configuration. The coordination polyhedron about copper(I) in 1 is best described as a distorted tetrahedron. Quasireversible redox behavior is observed for the complexes.     

Ferroelectric liquid crystal materials synthesized from 2(S)-[2(S)-methylbutyloxy]propanol

Abstract

A new chiral alcohol, 2(S)-[2(S)-methylbutyloxy]propanol (3), containing two chiral centres has been synthesized from ethyl lactate and (S)-1-iodo-2-methylbutane. It was used as a chiral building block for the preparation of ferroelectric liquid crystal materials. Several of the new materials exhibit an enantiotropic S*_c phase with a wide temperature range. The results indicate that the molecular structure of 3 is useful for synthesizing ferroelectric liquid crystal materials.     

Crystal and Molecular Structures of (E)-(2-Phenylethenyl)cyclooctatetraene and (E)-(2-(4-Nitrophenyl)ethenyl)cyclooctatetraene. Conformations of Substituted Cyclooctatetraenes

The single crystal x-ray structures of (E)-(2-arylethenyl)cyclooctatetraenes 1 and 2 have been determined. The nitro group in 2 does not influence the geometry of the COT ring relative to that of 1. The influence of various substituents on several structural parameters of the COT ring are analyzed in terms of steric/electrostatic and electronegativity effects of the substituent.     

Solvothermal Synthesis and Structure of Two 2D Tin–Selenides with Long Alkyldiamine NH2(CH2) n NH2 (n = 8, 10)

Reactions of NH₂(CH₂) _n NH₂ (n = 8,10) with elemental Sn and Se in a H₂O/CH₃OH mixture at 150°C afford two compounds (NH₃(CH₂)₈NH₃)Sn₃Se₇ (1) and (NH₃(CH₂)₈NH₃)Sn₃Se₇ (2). The crystal structures were determined by single crystal X-ray diffraction at room temperature. Both compounds exhibit the same anionic structure—a 6³ netted plane composed of [Sn₃Se₇]^2– subunits. The distance between the centers of crystal 1 layers is 7.5 Å, somewhat shorter than the distance (8.5 Å) in crystal 2.     

A coordination polymer with a (3,4)-connected (4·62)2(42 ·62 ·82) 2D network: synthesis,crystal structure and luminescent properties

The 2D Zn(II) coordination polymer with 2,3-dicarboxypyridine acid (2,3-H₂PDC) and dimethylamine (DMA) [Zn(2,3-PDC)(DMA)] _n (1) was synthesized under solvothermal conditions and characterized by FT-IR spectroscopy, TGA and luminescent analysis. X-ray crystallographic studies of 1 reveal that this metal-organic complex has an interesting (3,4)-connected 2D network with binary nodes. The Zn ions are four-connected nodes and the 2,3-PDC ligands are three-connected nodes. Luminescent study indicates 1 has an emissive maximum at 403?nm in the solid state at room temperature.     

Crystallographic and conformational analysis of two novel trans-azo benzene compounds

The molecular and crystal structure of (E)-2-Acetyl-4-(2-bromophenyldiazenyl)phenol (1) and (E)-2-Methyl-4-(o-tolyldiazenyl)phenol (2) were characterized and determined by single crystal X-ray diffraction method besides spectroscopic means. The periodic organization of 1 is stabilized by C–H···O type weak H-bond and Br···O type weak halogen bonding and thus, a two dimensional puckered network is established almost parallel to () the plane. Molecules of 2 are linked into C(7) chains generated by translation along the [1 0 1] direction with the aid of O–H···N type H-bonds, and these chains are strengthened by C–H···π interactions involving o-tolylphenol ring. Quantum chemical studies at B3LYP/6-311 ++G(d,p) level reveal that potential barrier of the compounds around Ar–N torsions is of double minimum character unless it is defected by the presence of o-substituent groups in the vicinity of the azo bridge. The results from crystallographic and quantum chemical studies suggest that azo benzene compounds may adapt non-planar geometry apart from the most stable planar conformation, which is located on the secondary minima of double potential barrier regarding rotational motion around Ar–N bonds.     

Supramolecular Ribbons. Crystal Structure and Spectroscopic Properties of 2,2′-Bipyrroyl

Summary.  A crystal structure determination of 2,2′-bipyrroyl (1; 2,2′-dipyrryl-diketone, bis (2-pyrrolyl)ethanedione) and its spectroscopic properties in solution are reported. In the crystal, 1 self-assembles via hydrogen bonding into supramolecular ribbons that extend indefinitely through the crystal lattice. The observed molecular conformation is one where each pyrrole ring and adjacent carbonyl group are co-planar (torsion angle ∼ 0.9°), with the N-H pointing in the same direction as the C=O. The two carbonyls have a transoid but not co-planar geometry with a torsion angle of ∼128°. Adjacent molecules in the crystal are linked by pairs of intermolecular hydrogen bonds, pyrrole NH to carbonyl oxygen, to form a matrix of polymeric chains that lie like neatly stacked, parallel streams of ribbons. Molecular mechanics calculations on the monomer indicate an intra-molecularly hydrogen bonded planar conformation (sp, ap, sp) at the global energy minimum. In CHCl₃, 1 is monomeric according to vapor pressure osmometry (MW _obs=179±10 vsċMW _calc=188). In THF, the measured molecular weight is 340±15, which corresponds best to one molecule of 1 solvated by two THF molecules (MW=322 for C₁₀H₈N₂O₄ċ2 C₄H₈O) rather than to a dimer. Received October 21, 1999. Accepted November 2, 1999     

A SHG-active manganese coordination polymer with noncentrosymmetric structure based on achiral carboxyphosphinate ligand

The hydrothermal reaction of MnSO₄ with the achiral 2-carboxyethyl(phenyl)phosphinate ligand (H₂L) afforded a 2?D coordination polymer manganese phosphinate, [Mn(HL)₂]_n (1) (H₂L?=?2-carboxyethyl(phenyl) phosphinic acid). It contains two types of dimeric ring motifs, which can generate a layer structure through edge-sharing. The interlayer stacking by C-H…π interactions between the C-H groups of the phenyl rings of HL^- and the phenyl rings of the adjacent layers results in its crystallization in a noncentrosymmetric crystal structure with (4³)₂(4⁶·6⁶·8³) topology. Compound 1 shows a second harmonic generation response that is 0.8 times that of urea. The luminescence spectrum indicates an emission maximum at 457?nm, attributed to an intra-ligand emission state.     

Supramolecular Ribbons. Crystal Structure and Spectroscopic Properties of 2,2′-Bipyrroyl

 A crystal structure determination of 2,2′-bipyrroyl (1; 2,2′-dipyrryl-diketone, bis (2-pyrrolyl)ethanedione) and its spectroscopic properties in solution are reported. In the crystal, 1 self-assembles via hydrogen bonding into supramolecular ribbons that extend indefinitely through the crystal lattice. The observed molecular conformation is one where each pyrrole ring and adjacent carbonyl group are co-planar (torsion angle ∼ 0.9°), with the N-H pointing in the same direction as the C=O. The two carbonyls have a transoid but not co-planar geometry with a torsion angle of ∼128°. Adjacent molecules in the crystal are linked by pairs of intermolecular hydrogen bonds, pyrrole NH to carbonyl oxygen, to form a matrix of polymeric chains that lie like neatly stacked, parallel streams of ribbons. Molecular mechanics calculations on the monomer indicate an intra-molecularly hydrogen bonded planar conformation (sp, ap, sp) at the global energy minimum. In CHCl₃, 1 is monomeric according to vapor pressure osmometry (MW _obs=179±10 vsċMW _calc=188). In THF, the measured molecular weight is 340±15, which corresponds best to one molecule of 1 solvated by two THF molecules (MW=322 for C₁₀H₈N₂O₄ċ2 C₄H₈O) rather than to a dimer.     

A Short and Elegant Synthesis of (±)‐Streptopyrrolidine

A brief and efficient approach for the synthesis of (±)‐5‐benzyl‐4‐hydroxy‐2‐pyrrolidine ( 1 ) from phenylalanine racemate is described. The key step is the stereocontrolled reduction of the keto functionality of benzylated pyrrolidinone intermediate ( 6 ) via sodium borohydride in carboxylic acid medium furnishing both (R,R)‐ and (S,S)‐configured diastereomers. The natural (R,R) enantiomer ( 2 ), however, crystallized out from its racemic mixture. Structure of 2 was confirmed by NMR, IR, elemental analyzer, and single crystal X‐ray crystallographic techniques.     

Study of the rearrangement of cyclononatetraenyl(dipropyl)borane to 7,8-dipropyl-7-borabicyclo[4.2.2]deca-2,4,9-triene by NMR spectroscopy

Using NMR spectroscopy it was found that at ambient temperature 9-cyclononatetraenyl(dipropyl)borane (1) rapidly rearranges to give 7,8-dipropyl-7-borabicyclo[4.2.2]deca-2,4,9-triene (2),cis-endo-9-dipropylborylbicyclo[6.1.0]nona-2,4,6-triene (3a), and two isomeric boranes with dihydroindene skeletons (4a,b) (the ratio2 :3a :4a,b is 10 : 1 : 2).cis-exo-9-Dipropylborylbicyclo[6.1.01nona-2,4,6-triene (3b) is an intermediate product of the rearrangement; it is formed as a result of 8-electrocyclization inE,Z,Z,Z-cyclononatetraenyl(dipropyl)boranela. The transformation of bicycle3b to final product 2 occurs apparently via a synchronous exchange of the groups at the B atom (the transformation of the cyclopropane ring to the boracyclobutane ring accompanied by simultaneous migration of the propyl group from the B atom to thea-C atom). Borane6 formed in this rearrangement rapidly isomerizes to2 via a [1,3]-B shift.For preliminary report see Ref. 1Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. I, pp. 117–124, January, 1996.     

Three new 3,4-seco-cycloartane triterpenes from Gardenia sootepensis

The plants in the genus Gardenia (Rubiaceae) have long been used as traditional medicines in China. In this study, two new 3,4-seco-cycloartane triterpenes, sootepin J (1) and sootepin K (2), and a novel nor-3,4-seco-cycloartane triterpenes, sootepin L (3), together with two known compounds (4–5), were isolated from the methanolic extract of the leaves and twigs of Gardenia sootepensis. The structures of the new compounds were elucidated by combinations of 1D, 2D NMR experiments and HR-MS data, while the known compounds were identified by comparison of the NMR data with previously published data.     

Synthesis and liquid crystal properties of a new class of calamitic mesogens based on substituted 2,5‐diaryl‐1,3,4‐thiadiazole derivatives with wide mesomorphic temperature ranges

Liquid crystals based on substituted 2,5‐diaryl‐1,3,4‐thiadiazole derivatives (1a–1f, 3a and 3b) and 1,3,4‐oxadiazole analogues (2a–2f, 4a and 4b) were synthesised and characterised by ¹H, ¹³C nuclear magnetic resonance, Fourier transform infrared, mass spectrometry, high‐resolution mass spectrometry techniques and elemental analyses. The X‐ray crystal structure of 1e revealed that it contains tilted lamellar arrangement of molecules in the crystalline solid. The liquid crystal properties have been investigated by polarised‐light optical microscopy, differential scanning calorimetry and in‐situ variable‐temperature X‐ray diffraction. All compounds (except 2e and 2f) exhibited thermotropic liquid crystal behaviours with various mesophases (smectic A and C, nematic N or soft crystal E phases). Notably, the 1,3,4‐thiadiazole derivatives consistently have wider mesomorphic temperature ranges than those of the respective 1,3,4‐oxadiazole analogues. The solutions of all compounds in CH₂Cl₂ individually displayed one or two absorption bands with λ _max values at 297–355 nm and emitted with λ _max values at 363–545 nm and quantum yields of 0.12–0.73. Structure–property relationships of these compounds are discussed in the contexts of their molecular structures and weak intermolecular interactions.     

Syntheses,crystal structures and thermal analyses of two new ionic complexes based on 3,4-diamino-1,2,4-triazole

Two new ionic complexes, (DATr)₂[Li₂(TNR)₂·2H₂O]·2H₂O (1) and (DATr)[Zn(DATr)Cl₃] (2), were synthesized by using 3,4-diamino-1,2,4-triazole (DATr) as outer cation. X-ray single-crystal diffraction analysis revealed that the two complexes crystallize in triclinic and orthorhombic crystal systems, respectively. Differential scanning calorimetry was applied to assess the thermal decomposition behavior and kinetic parameters of decomposition were studied by using Kissinger’s and Ozawa–Doyle’s methods. Furthermore, the critical temperature of thermal explosion and parameters of thermodynamics were obtained.     

Comparative study on two 2-pyrazoline derivatives with experimental and theoretical methods

Two 2-pyrazoline derivatives of 1-phenyl-3-(4-chlorophenyl)-5-(2-chlorophenyl)-2-pyrazoline (1) and 1-phenyl-3-(4-methylphenyl)-5-(2-chlorophenyl)-2-pyrazoline (2) have been synthesized and characterized by elemental analysis, IR, UV–Vis, and fluorescence spectra. The crystal structure of 2 has been determined by X-ray single crystal diffraction. For the two compounds, density functional theory (DFT) calculations of the structures and natural population atomic charge analysis have been performed at B3LYP/6-311G** level of theory. By using TD-DFT method, electron spectra of 1 and 2 have been predicted, which are in good agreement with the experimental ones. Comparative studies on 1 and 2 indicate that the change of substituted groups in 3-phenyl ring of pyrazoline ring will change the peak intensity and peak locations both in electron spectra and fluorescence spectra.