Molecular structure of 2,3-(4′-phenylacetyl)- and 2,3-(4′-diphenylacetyl)-benzo-15-crown-5

The conformational state of two benzo-crown ethers with substantially different physiological activity, 2,3-(4-phenylacetyl)- and 2,3-(4-diphenylacetyl)benzo-15-crown-5, was studied in crystals and solutions in CH₃CN and CCl₄ by x-ray crystallographic analysis, IR spectroscopy, and conformational calculations by the method of molecular mechanics. Transition from the crystalline state to solutions was found to be accompanied by a substantial change in the conformation of the macrocyclic ring of all the compounds studied. The nature of the substituent in the benzene ring and the polarity of the solvent have an influence on the conformational state of the macrocyclic ring of the free ligand, which, however, is not the determining factor in the change in the activity of the compounds. The COCCOC fragments of the macrocyclic framework are conformationally labile, readily passing from gauche to trans conformations and the reverse, which is promoted by the negligible energy barriers between the different conformations, determined in the work by a molecular mechanics method.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 8, pp. 1819–1825, August, 1991.     

Five-membred 2,3-dioxoheterocycles: LXXXI. Reactions of 4,5-bis(methoxycarbonyl)-1H-pyrrole-2,3-diones with N-substituted 3-amino-5,5-dimethyl-2-cyclohex-2-en-1-ones. crystal and molecular structure of methyl 4′-hydroxy-6,6-dimethyl-1,1′-bis(4-methylphenyl)-2,4,5′-trioxo-1,1′,2,4,5,5′,6,7-octahydrospiro[indole-3,2′-pyrrole]-3′-carboxylate

1-Aryl-4,5-bis(methoxycarbonyl)-1H-pyrrole-2,3-diones react with N-substituted 3-amino-5,5-dimethylcyclohex-2-en-1-ones affording methyl 1,1′-diaryl-4′-hydroxy-6,6-dimethyl-2,4,5′-trioxo-1,1′,2,4,5,5′,6,7-octahydrospiro[indole-3,2′-pyrrole]-3′-carboxylates whose structure was proved by XRD analysis.     

Regioselective silylation of 5-(2′-hydroxyethyl)cyclopent-2-en-1-ol and 6-(2′-hydroxyethyl)cyclohex-2-en-1-ol

Herein we report regioselective and mild reactions for the tert-butyldimethylsilyl mono-protection of 5-(2′-hydroxyethyl)cyclopent-2-en-1-ol (2) and 6-(2′-hydroxyethyl)cycohex-2-en-1-ol (5) at the primary hydroxyl group or at the secondary allylic hydroxyl group. The different steric environment surrounding the secondary allylic and saturated primary alcohols is mainly invoked to rationalize the observed regioselectivity.     

Molecular and crystal structure of 4,5,4′,5′-tetrahydro-2,2′-(1,4-phenylene)bisoxazoline

4,5,4,5-Tetrahydro-2,2-(1,4-phenylene)bisoxazoline, which is one of the most promising stabilizers-consolidators of heterochain polymers, was studied by X-ray structural analysis.Deceased.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 2506–2507, October, 1996.     

Synthesis and liquid crystal properties of dinuclear cyclopalladated 5-alkyl-2-(4′-alkoxyphenyl)pyrimidine and 3-(4′-alkoxyphenyl)-6-alkoxypyridazine complexes

The dinuclear cyclopalladated complexes [Pd(L₁ or L₂)(µ-X)]₂ (HL₁=5-alkyl-2-(4′-alkoxyphenyl)pyrimidine, HL₂=3-(4′-alkoxyphenyl)-6-alkoxypyridazine, X=Cl^?, CH₂ClCOO^?, CH₂BrCOO^?, CH₃CHBrCOO^?, CH₂BrCH₂COO^?, CH₃COO^?) have been synthesized and characterized; their mesogenic properities were determined by DSC and polarizing microscopy. The effect of the bulk and the polarity of the bridging ligands on their mesogenic properties is discussed. The effect of the length of the alkyl chains on the mesogenic properties of these organometallic complexes has also been investigated.     

Synthesis of N-Aryl-2-(1′,6′-dihydro-6′-pyridazinone-3′-carbonyl) Thiosemicarbazides and Their Related Heterocyclic Compounds

Introduction Somepyridazineshavebeenexaminedforac- tivityagainstsporozoanandflagellateparasitesand forantiamebicactivity[1]. 6-Aryl-4,5-dihydro-3(2H)-pyridazinonesex- hibitvariousbiologicalpropertiesincludingreduc- tionofbloodpressure,inhibitionofplateletaggre- gation,antiinflammation,andstrongplateletag- gregationinhibitingactioncoupledwithahypoten- siveaction.Italsopossessesweakpositiveinotrop- icactivityforthemanagementofcongestiveheart failure.Threepara-substitueddihydropyridazi- nonesare…     

Synthesis,structure, and physico-chemical properties of 3-methyl and 3,3-dimethyl derivatives of l-(4′,4′-dimethyl-2′,6′-dioxocyclohex-1′-yl)-3,4-dihydroisoquinoline

3,3-Dimethyl- and 3-methyl-1-(4,4-dimethyl-2,6-dioxocyclohex-1-yl)-3,4-dihydroisoquinolines have been synthesized. Crystal and molecular structures of the 3,3-dimethyl derivative have been determined. In the crystalline state this compound exists as a tautomeric form where a hydrogen atom is located at the N atom of the dihydroisoquinoline fragment of the molecule. The tautomeric equilibrium does not shift noticeably in solutions, as shown by IR, UV, and NMR spectroscopy.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 331–336, February, 1993.     

Molecular and crystal structure of 19-nor-4α(6-hydrazonocarbonyl-3,4,5-trihydroxytetrahydropyran-2-oxycarbonyl)-16-hydrazono-ent-beyeran

Russian Chemical Bulletin - X-ray crystallography was used to study molecular and crystal structure of...     

Molecular and crystal structure of 2-phenoxy-2λ5-2,2′(3H,3′H)-spirobi[1,3,2-benzoxazaphosphole]

The crystal and molecular structure of 2-phenoxy-2⁵-2,2(3H,3H)-spirobi[1,3,2-benzoxazaphosphole] has been determined using X-ray diffraction structure analysis. The P atom in the molecule in question has a distorted trigonal bipyramidal coordination, with the bond lengths P-O_ax=1.701(1) and 1.700(1) Å, P-O_eq (Ph)=1.625 Å, P-N_eq=1.654(2) and 1.645(1) Å, and bond angles (O-P-O)_ax=175.69(7)° and (N-P-N)_eq = 132.38(7)°.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 876–879, May, 1993.     

The molecular and crystal structure of N-(4-n-butyloxybenzylidene)-4′-ethylaniline (4O.2) and N-(4-n-heptyloxybenzylidene)-4′-hexylaniline (7O.6)

Abstract

The molecular and crystal structure of N-(4-n-butyloxybenzylidene)-4′-ethylaniline (4O.2) and the homologue N-(4-n-heptyloxybenzylidene)-4′-hexylaniline (7O.6) have been solved (at room temperature) by direct methods. The crystals of both compounds belong to the triclinic system with space group P1 with two molecules per unit cell. 4O.2: a = 5·531(2), b = 7·592(3), c = 19·746(7) Å, α = 86·66(2), β = 88·15(2), γ = 90·29(2)° 7O.6: a = 5·420(2), b = 8·307(3), c = 28·057(7) Å, α = 91·69(2), β = 89·76(2), γ = 108·02(2)°. The structures were refined by full-matrix least-squares calculations to R = 0·036 for 2297 observed reflections for 4O.2 and to R = 0·037 for 2150 reflections for 7O.6. The conformations in the asymmetric units of the two compounds differ considerably: The planes of the two phenyl rings of 4O.2, forming the mesogenic core of the molecule, are twisted at 61·2° to each other and the butoxy group contains a gauche conformation. In contrast the heptoxy chain of 7O.6 forms an all trans-conformation which lies almost in one plane with the two coplanar phenyl rings. The hexyl group also exists in an extended form, in a plane which is rotated against the plane of the mesogenic unit. The packing in the crystalline state of the two homologues exhibits a layered structure along c*; in 4O.2 these layers are separated, but in 7O.6 they are interdigitated. The compensation of the dipole moments of the C?O?C and C?N?C bonds occurs similarly in both structures: molecular orientations parallel to the a, c-plane in which the long axes of the molecules points in the same direction are packed in antiparallel fashion along b*.     

Crystal-state conformation of homo-oligomers of α-aminoisobutyric acid: Molecular and crystal structure of pBrBz-(Aib)6-OMe

A synthetic, terminally blocked homohexapeptide from-aminoisobutyric acid has been examined by single-crystal X-ray diffraction and the structure refined toR = 0.047. The compound is folded into almost two turns of a 3₁₀-helix, stabilized by four consecutive intramolecular N—H·O=C H-bonds. An asymmetric covalent geometry for the-aminoisobutyric acid residues, known to be responsible for the onset of the 3₁₀-helix in homopeptides from this C^,-dialkylated-aminoacid on the basis of a theoretrical conformational analysis, has been experimentally found also in this structure.     

Synthesis of Dimedone-Annelated Heterocycles: Regioselective Heterocyclization of 2-(Cyclohex-2′-enyl)-5,5-dimethyl-3-hydroxy cyclohex-2-enone

Abstract

2-(Cyclohex-2′-enyl)-5,5-dimethyl-3-hydroxycyclohex-2-enone undergoes regioselective heterocyclization to give bridged heterocycles 5a,b and 7 on treatment with pyridine hydrotribromide or hexamethylenetetramine hydrotribromide (1 h); or elemental bromine (7 h); N-iodosuccinimide in acetonitrile at 0–5°C (1 h) and conc. H₂SO₄ at 0–5°C (2 h), respectively.     

Crystal and molecular structures of (3Z)-(±)-4-(2′-hydroxypropyl)amino-and (3Z)-4-(2′-hydroxyethyl)amino-pent-3-en-2-ones

An X-ray study of (3Z)-(±)-4-(2′-hydroxypropyl)amino-and (3Z)-4-(2′-hydroxyethyl)amino-pent-3-en-2-ones is reported. The bond lengths inside the H ring are equalized due to the classical N-H...O hydrogen bond between the carbonyl oxygen and the amino group. In the 4-(2′-hydroxyethyl)amino-pent-3-en-2-one crystal, due to the classical N-H...O bonds, infinite zigzag chains are formed along the 0b axis and arranged into a layered structure due to the weak C-H...O interactions. In (±)-4-(2′-hydroxypropyl)aminopent-3-en-2-one crystal, however, centrosymmetric dimers are formed, which are then linked by weak C-H...O intermolecular interactions to form a layered structure along the a0b plane.     

Investigations in the region of 2,3′-biquinoline. 3. Synthesis of 2′-alkyl(aryl)-1′,2′-dihydro-2,3′-biquinolines and 2′-alkyl(aryl)-2,3′-biquinolines

A method was developed for the synthesis of 2-alkyl(aryl)-1,2-dihydro-2,3-biquinolines, based on the addition of organolithium compounds to 2,3-biquinoline in the presence of tetramethylethylenediamine. Their oxidation with manganese dioxide led to 2-alkyl(aryl)-2,3-biquinolines.For Communication 2, see [1].Stavropol State University, Stavropol 355009, Russia. Russian Chemical-Technology University, Moscow 125190. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 350–354, March, 1998.     

Molecular dynamics and alignment studies of silica-filled 4-pentyl-4′-cyanobiphenyl (5CB) liquid crystal

A comprehensive study of the dielectric properties of 4-pentyl-4′-cyanobiphenyl (5CB) liquid crystal filled with silica particles (particle size 30–80 nm, concentration 2, 3, 5, 10 and 15 wt%). Dielectric spectroscopy in the frequency range 100 to 10 7 Hz was applied to investigate the influence of the filler on the dynamic behaviour of the liquid crystal molecules in both the nematic and isotropic phases. In this frequency range one relaxation process is observed (at f>10⁶ Hz). The dynamical behaviour of the 5CB liquid crystal is described by the Cole-Cole relaxation function. The temperature dependence of the relaxation time obeys the empirical Arrhenius equation. The activation energies are approximately 75 kJ mol¹ for the pure 5CB sample in the nematic phase and 50 kJ mol¹ for the 5 wt% silica-filled 5CB sample. These values are compared with the corresponding literature values. The reversible electro-mechanical response of these samples under the influence of an applied a.c. electric field is investigated.     

Cubic phases of binary systems of 4′-n-tetradecyloxy-3′-nitrobiphenyl-4-carboxylic acid (ANBC-14)-n-alkane

The phase behaviour of the binary systems 4′- ⁿ -tetradecyloxy-3′-nitrobiphenyl-4-carboxylic acid (ANBC-14)- ⁿ -alkane ( ⁿ -tetradecane or ⁿ -hexadecane) was investigated by differential scanning calorimetry, polarizing optical microscopy, and X-ray diffraction. The phase behaviour was a function of temperature ( ^T ) and the effective carbon number of the system ( ^n*), where ^n* involves carbon atoms both from the alkoxy group of ANBC-14 and from the ⁿ -alkane added. ANBC-14 shows no cubic phase, but the addition of ⁿ -alkane induced cubic phases when ^n*≧c. 15. An interesting point is that the type of cubic phase is ^Ia 3 ^d for 15^≦n*≦17, while an ^Im 3 ^m type is formed for 18^≦n*≦20. Furthermore, for ^n* = 22, two types of cubic phase, one with ^Im 3 ^m symmetry in the low temperature region and the other with ^Ia 3 ^d in the high temperature region, were observed both on heating and cooling. The phase diagram with respect to ^T and ^n* is very similar to that of pure one-component ANBC- ⁿ , which is a function of ^T and the number of carbon atoms in the alkoxy group ⁿ .     

Molecular and crystal structure of iron(III) and nickel(II) complexes with 1′-phthalazinylhydrazones of heterocyclic carbonyl compounds

Journal of Structural Chemistry - The structures of iron(III) and nickel(II) complexes with the composition [FeL2]Cl·H2O (1) and [Ni(HL′2)]·DMSO·0.5H2O (2), where L and...     

Five-membered 2,3-dioxo heterocycles: LXIII. Cascade recyclization of isopropyl 2-(1-aryl-4,5-dioxo-2-phenyl-4,5-dihydro-1H-pyrrol-3-yl)-2-oxoacetates with cyclic enamines. Crystalline and molecular structure of 1′-benzyl-6′,6′-dimethyl-3-[(Z)-phenyl(phenylamino)methylidene]-6′,7′-dihydro-3H-spiro[furan-2,3′-indole]-2′,4,4′,5(1′H,5′H)-tetraone

Isopropyl 2-(1-aryl-4,5-dioxo-2-phenyl-4,5-dihydro-1H-pyrrol-3-yl)-2-oxoacetates reacted with N-substituted 3-amino-5,5-dimethylcyclohex-2-en-1-ones to give the corresponding 1′-substituted (Z)-6′,6′-dimethyl-3-[phenyl(arylamino)methylidene]-6′,7′-dihydro-3H-spiro[furan-2,3′-indole]-2′,4,4′,5(1′H,5′H)-tetraones. The structure of 1′-benzyl-6′,6′-dimethyl-3-[(Z)-phenyl(phenylamino)methylidene]-6′,7′-dihydro-3Hspiro[furan-2,3′-indole]-2′,4,4′,5(1′H,5′H)-tetraone was proved by X-ray analysis.