Synthesis of ethyl (2<Emphasis Type="Italic">E</Emphasis>,4<Emphasis Type="Italic">E</Emphasis>)- and (2<Emphasis Type="Italic">E</Emphasis>,4<Emphasis Type="Italic">Z</Emphasis>)-5-chloropenta-2,4-dienoates

An efficient synthetic approach to 2E,4E and 2E,4Z isomers of ethyl 5-chloropenta-2,4-dienoate has been developed on the basis of one-pot oxidation–olefination of readily accessible (E)- and (Z)-3-chloroprop-2-en-1-ols by the action of barium manganate and ethyl (triphenyl-λ⁵-phosphanylidene)acetate.     

Syntheses of (<Emphasis Type="Italic">E</Emphasis>)- and (<Emphasis Type="Italic">Z</Emphasis>)-3-styrylchromones

Several (E)- and (Z)-3-styrylchromones were prepared by two different methodologies, the Wittig reaction of chromone-3-carboxaldehyde with benzylic ylides and the Knoevenagel condensation of chromone-3-carboxaldehyde with phenylacetic acids in the presence of potassium tert-butoxide under microwave irradiation. The Knoevenagel reaction followed by a decarboxylation offered an efficient and diastereoselective method for preparing (E)-3-styrylchromones in a shorter reaction time. It was also demonstrated that phenylacetic acid can also be substituted with success by phenylmalonic acid. The stereochemistry of all products was assigned by NMR experiments. Correspondence: Artur M. S. Silva, Chemistry Department, University of Aveiro, 3810-193 Aveiro, Portugal.     

<Emphasis Type="Italic">Z</Emphasis>-and <Emphasis Type="Italic">E</Emphasis>-conformers of <Emphasis Type="Italic">N</Emphasis>-chloroacetylcytisine

N-Chloroacetylcytisine was synthesized by acylation of (–)-cytisine. Stable Z- and E-conformers with respect to rotational isomerism around the N-12–CO bond were found in PMR spectra at room temperature. The point at which PMR resonances of the Z- and E-conformers coalesced upon heating was measured. The transition barrier between the conformers was estimated.     

Synthesis of (<Emphasis Type="Italic">E</Emphasis>)- and (<Emphasis Type="Italic">Z</Emphasis>)-3(5)-(2-hydroxyphenyl)-4-styrylpyrazoles

Abstract  An efficient synthesis method for the preparation of a series of new (Z)- and (E)-3(5)-(2-hydroxyphenyl)-4-styrylpyrazoles was developed. The reaction of (Z)- and (E)-3-styrylchromones with hydrazine hydrate afforded the corresponding (Z)- and (E)-3(5)-(2-hydroxyphenyl)-4-styrylpyrazoles, except for nitro derivatives, where both (Z)- and (E)-4′-nitro-3-styrylchromones afforded (E)-3(5)-(2-hydroxyphenyl)-4-(4-nitrostyryl)pyrazoles. The reaction mechanism for these transformations is discussed and the stereochemistries of all products were established by NMR experiments. Graphical abstract        

Regioselectivity and regiospecificity of phosphorylation of (<Emphasis Type="Italic">Z</Emphasis>)- and (<Emphasis Type="Italic">E</Emphasis>)-4-chloromethylene-2-phenyl-5(4<Emphasis Type="Italic">H</Emphasis>)-oxazolones. Effect of solvation: Supramolecular approximation

By the methods of quantum chemistry in supramolecular approximation, are considered stereochemical and energetic features of phosphorylation of 4-chloromethylene-2-phenyl -5(4H)-oxazolone Z- and E-isomers in gas phase and their solvates with acetonitrile of 1:n composition where n varies from 1 to 10. On the MNDO-PM3 level the phosphorylation with triphenylphosphine proceeds endothermally in two steps: nucleophilic addition in the first step and elimination of chlorine anion with formation of phosphonium salt in the second step. Solvation with acetonitrile leads to stabilization of phosphonium intermediate and decrease in heat of conversion. On both semiempirical and nonempirical levels occur regioselectivity of nucleophilic attack at the double C=C, but not C=O, bond and regiospecificity of transformation without inversion of init configuration of the isomers owing to steric hindrances restricting rotation degree of freedom of -CHClP⁺Ph₃ group. Therewith, elimination of chlorine anion is characterized by low activation barrier and occurs with donation negative charge from π-orbital of carbon atom in the 4 position of heterocycle on antibonding σ*-orbital of carbon-chlorine bond; two orbitals become practically coplanar in the transition state.     

Rapid SnCl<Subscript>2</Subscript> catalyzed phenylselenoetherification of (<Emphasis Type="Italic">Z</Emphasis>)- and (<Emphasis Type="Italic">E</Emphasis>)-hex-4-en-1-ols

A fast and efficient method for intramolecular heterocyclization of (Z)- and (E)-hex-4-en-1-ols was developed. The method does not cause side reactions of the substrates and provides the cyclic phenylselenoethers in high yields after only few minutes. A catalytic amount of SnCl₂ increased the yield, but in the presence of an equimolar amount of SnCl₂, formation of corresponding cyclic ethers were almost quantitative and reaction occurred instantaneously under extremely mild experimental conditions. Correspondence: Zorica M. Bugarčić, Department of Chemistry, Faculty of Science, University of Kragujevac, Radoja Domanovića 12, P.O.Box 60, YU-34000 Kragujevac, Serbia.     

Stereoselective synthesis of (<Emphasis Type="Italic">Z</Emphasis>,<Emphasis Type="Italic">E</Emphasis>)-bis(2-chloroethenyl)tellanes

A procedure for the stereoselective synthesis of dichloro[(Z)-2-chloro-2-phenylethenyl][(4E)-5- chlorooct-4-en-4-yl]-λ⁴-tellane and [(Z)-2-chloro-2-phenylethenyl][(4E)-5-chlorooct-4-en-4-yl]tellane has been developed on the basis of anti-addition of tellurium tetrachloride–phenylacetylene monoadduct to oct-4-yne.     

Crystallographic and conformational analysis of (<Emphasis Type="Italic">E</Emphasis>)-2-isopropyl-4-(<Emphasis Type="Italic">p</Emphasis>-tolyldiazenyl)phenol

The molecular and crystal structures of the title compound, C₁₆H₁₈N₂O, were characterized and determined by single crystal X-ray diffraction method in addition to spectroscopic means such as IR, UV–VIS and ¹H NMR. The compound crystallizes in orthorhombic space group P bca, with a = 9.3350(5) Å, b = 23.4878(13) Å, c = 26.5871(12) Å, Z = 16, D _calc. = 1.1591(1) g/cm³, μ (MoK_α) = 0.073 mm^?1. Monomers of the compound in the crystal structure are linked into C(7) and C(8) chains generated by translation along the [1 0 0] direction with the aid of O–H···N type H-bonds which serve to the stabilization of periodic organization of the molecules beside major and minor component in the disordered azo fragment. In order to describe conformational flexibility and the crystal packing effects on the molecular conformation, potential barriers regarding the rotation along both Ar–N bonds were calculated by varying the related torsional degrees of freedom in every 10° ranging from ?180° to +180° via quantum chemical calculations at DFT/B3LYP level.     

Synthesis of (<Emphasis Type="Italic">E</Emphasis>)-<Emphasis Type="Italic">N</Emphasis>-(3-alkoxy-4-acyloxyphenylmethylene)-<Emphasis Type="Italic">N</Emphasis>-(<Emphasis Type="Italic">e</Emphasis>-cyclohexyl)amines

Previously unknown E isomers of azomethines (Schiff bases) were synthesized from vanillal and vanillin esters by their reaction with cyclohexylamine.     

Synthesis of <Emphasis Type="Italic">N,N</Emphasis>-disubstituted (<Emphasis Type="Italic">Z</Emphasis>)-<Emphasis Type="Italic">O</Emphasis>-methylnicotinamide oximes

A number of (Z)-N,N-dialkyl- and (Z)-N-acyl-N-alkyl-O-methylnicotinamide oximes was synthesized. Their configuration was confirmed by the NOESY experiment. Evaluation of fungicidal activity of compounds obtained was performed.     

Isomeric form and proton localization in (9<Emphasis Type="Italic">E</Emphasis>)-phenanthrene-9,10-dione[(1<Emphasis Type="Italic">Z</Emphasis>)-3,3-dimethyl-3,4-dihydroisoquinolin-1(2<Emphasis Type="Italic">H</Emphasis>)-ylidene]hydrazonium bromide

(9E)-Phenanthrene-9,10-dione[(1Z)-3,3-dimethyl-3,4-dihydroisoquinolin-1(2H)-ylidene]hydrazonium bromide (LH)Br (I) was synthesized. The models of protonated forms of the LH⁺ cation were calculated by quantum-chemical methods, and their relative stability was estimated. The crystal structure of compound I was determined by X-ray diffraction analysis. Compound I is built according to the cation-anion type (the mobile protons are located at the nitrogen atoms). The cation exists in the s-cis,cis-isomeric form stabilized by two cyclic hydrogen bonds. The π-electron density is localized on the multiple bonds N(1)-C(1) (1.292(4) Å) and N(3)-C(12) (1.294(4) Å). the spectroscopic characteristics (IR and electronic absorption spectra) of compound I are obtained.     

Prilezhaev dihydroxylation of (<Emphasis Type="Italic">R</Emphasis>)-octadec-9<Emphasis Type="Italic">Z</Emphasis>-en-7-0l

Formation of new asymmetric centers with primarily the (S)-configuration was induced by the optically active center of (R)-octadec-9Z-en-7-ol upon Prilezhaev dihydroxylation. This was proved by cyclization of a 1,3-glycol system (de 26%) into the corresponding 1,3-dioxane stereoisomers.     

Structure,Anticorrosion and Antibacterial Evaluation of (<Emphasis Type="Italic">E</Emphasis>)-3-(<Emphasis Type="Italic">N</Emphasis>-Oxide-methylimino)indolin-2-one

A nitrone, (E)-3-(N-oxide-methylimino)indolin-2-one, was synthesized and analyzed by X-ray single crystal analysis. The inhibition and the mechanism of action of the title compound on the corrosion of high protective Q235A steel in HCl solution were screened and discussed by weight loss and electrochemical measurements. The mechanism of action of (E)-3-(N-oxide-methylimino)indolin-2-one in HCl solution was screened for the corrosion of N80 steel in 1-methylindolin-2-one solution, and the inhibition mechanism was discussed. The results indicated that it can inhibit the corrosion with moderate inhibition efficiency in different conditions, and the mechanism of the corrosion inhibiting may be mainly contributed to the adsorption. It was screened for antibacterial activity against oilfield water-borne bacteria, and it showed good to moderate activity against sulfate reducing bacteria.     

Synthesis of (2<Emphasis Type="Italic">E</Emphasis>,4<Emphasis Type="Italic">E</Emphasis>)-dodeca-2,4-dien-1-yl isovalerate,the main component of rootstock oil of <Emphasis Type="Italic">Echinacea purpurea</Emphasis>

By phosphine-free Heck reaction a stereoselective synthesis was performed of (2E,4E)-dodeca-2,4-dien-1-yl isovalerate, the main component of the rootstock oil of Echinacea purpurea.     

Synthesis of chiral glycolurils from (<Emphasis Type="Italic">S</Emphasis>)-(+)- and (<Emphasis Type="Italic">R</Emphasis>)-(-)-1-<Emphasis Type="Italic">sec</Emphasis>-butyl-3-methylurea

Chiral dialkyl- and tetraalkylglycolurils have been obtained using chiral (S)-(+)- and (R)-(-)-1-sec-butyl-3-methylurea as starting materials. The diastereomer (S)-(+)-2,6-di-sec-butyl-4,8-dimethyl-2,4,6,8-tetraazabicyclo[3.3.0]-octane-3,7-dione was separated into stereoisomers, for the higher melting of which the absolute configuration was determined as (S,S,S,S) by X-ray structural analysis.     

Synthesis of 5<Emphasis Type="Italic">Z</Emphasis>,9<Emphasis Type="Italic">E</Emphasis>-tridecadien-1-ylacetate,an attractant of <Emphasis Type="Italic">Trichoplusia ni</Emphasis>

A new synthetic scheme for 5Z,9E-tridecadien-1-ylacetate, an attractant of the cabbage looper Trichoplusia ni (Huebner) was developed using a highly stereoselective Claisen rearrangement.     

Synthesis,spectroscopic characterization,crystal structures,and theoretical studies of (<Emphasis Type="Italic">E</Emphasis>)-2-(2,4-dimethoxybenzylidene)thiosemicarbazone and (<Emphasis Type="Italic">E</Emphasis>)-2-(2,5-dimethoxybenzylidene)thiosemicarbazone

Two thiosemicarbazones, (E)-2-(2,4-dimethoxybenzylidene)thiosemicarbazone (24-MBTSC (1)) and (E)-2-(2,5-dimethoxybenzylidene)thiosemicarbazone (25-MBTSC (2)), derived from 2,4-dimethoxybenzaldehyde and 2,5-dimethoxybenzaldehyde, respectively, with thiosemicarbazide have been synthesized and their structures were characterized by elemental analyses, FT-IR, ¹H NMR spectroscopy, and X-ray single-crystal diffraction analysis. Molecular orbital calculations have been carried out for 1 and 2 by using an ab initio method (HF) and also density functional method (B3LYP) at 6-31G basis set. Compound 1 crystallizes in the monoclinic system, space group P2₁/c, with a = 8.1342(5) Å, b = 18.1406(10) Å, c = 8.2847(6) Å, β = 109.7258(17)°, V = 1150.75(12) Å³, and Z = 4, whereas compound 2 crystallizes in the orthorhombic system, space group Pbca, with a = 11.0868(6) Å, b = 13.1332(6) Å, c = 15.9006(8) Å, V = 2315.2(2) Å³, and Z = 8. The compounds 1 and 2 displays a trans-configuration about the C=N double bond.     

Oxidative trifluoroacetamidation of (1<Emphasis Type="Italic">E</Emphasis>,3<Emphasis Type="Italic">E</Emphasis>)-1,4-diphenylbuta-1,3-diene and 1,1,4,4-tetraphenylbuta-1,3-diene

Reactions of trifluoroacetamide with (1E,3E)-1,4-diphenylbuta-1,3-diene and 1,1,4,4-tetraphenylbuta-1,3-diene in the oxidative system t-BuOCl–NaI have been studied. The reaction with (1E,3E)-1,4-diphenylbuta-1,3-diene afforded three products, N,N′-(phenylmethylene)bis(trifluoroacetamide), 3-chloro-4-iodo- 2,5-diphenyl-1-(trifluoroacetyl)pyrrolidine, and trifluoro-N-[(3E)-2-hydroxy-1,4-diphenylbut-3-en-1-yl]acetamide, with a high overall yield. 1,1,4,4-Tetraphenylbuta-1,3-diene failed to react with trifluoroacetamide.     

Conformational analysis and crystal structure of (<Emphasis Type="Italic">E</Emphasis>)-3-methyl-4-(<Emphasis Type="Italic">p</Emphasis>-tolyldiazenyl)phenol

The single crystal X-ray diffraction analysis of the title compound, C₁₄H₁₄N₂O, reveals that an interesting intermolecular or extended structure (hydrogen-bonded polymeric zigzag chains) is formed by linking its monomer units with O–H···N type intermolecular hydrogen bonds. The compound crystallizes in the monoclinic space group P2₁/n with a = 5.8151(5) Å, b = 18.106(1) Å, c = 11.515(1) Å  and β = 96.891(7)°. In order to understand better its structural aspects in solid state, quantum chemical (PM3) calculations were performed on a part of the extended structure of the title compound containing ten monomers. To determine in vacuo conformational flexibility of the compound, molecular energy profile of the title compound was obtained with respect to a selected torsional degree of freedom and the pedal angle varied from ?180° to +180° in every 10°. The results from the computational study suggest that hydrogen-bonding properties in the crystal lattice is fundamental in determining the crystallographically observed conformation of the title compound.     

Two new isomeric lignans from <Emphasis Type="Italic">Eusideroxylon zwageri</Emphasis>

Two new lignans were isolated with two other known compounds, eusiderin A and eusiderin I, from Eusideroxylon zwageri (billian). The two new lignans have isomeric structure. The structures of the new lignans were determined to be (2R,3R,4S)-2,3-dimethyl-6,7-dimethoxy-4-ethoxy (3′,4′,5′-trimethoxybenzene)-1,5-dihydroxytetralin and (2R,3S,4S)-2,3-dimethyl-6,7-dimethoxy-4-ethoxy(3′,4′,5′-trimethoxybenzene)-1,5-dihydroxytetralin. Published in Khimiya Prirodnykh Soedinenii, No. 3, pp. 303–305, May–June, 2009.