Identification of some isomeric 3,5-unsymmetrically substituted 1-aroyl-pyrazole derivatives by NMR spectroscopy

The ¹H and ¹³C nmr chemical shifts are used for the structural assignment of isomeric 1-aroyl-4,5-dihydro-5-hydroxy-4,4-dimethyl-1H-pyrazoles 1 unsymmetrically substituted with phenyl or methyl in the 3,5-positions of the pyrazole ring. The ¹H nmr spectra of 1-aroyl- or 1-acetyl-4-methyl-1H-pyrazoles 2 are useful in structure elucidation of unsymmetrically 3- or 5-methyl substituted derivatives.     

Syntheses,Spectroscopy and Calculated Second-Order Nonlinear Optical Properties of a New Series of Square-Pyramidal Substituted Phenylthiourea Zinc(II) Complexes

A new series of square-pyramidal coordination compounds L·Zn(acac)₂ (acac = acetylacetonate; L is a variety of substituted phenylthioureas: p-N,N ′-dimethylaminophenylthiourea 1, p-methoxy-phenylthiourea 2, p-nitrophenylthiourea 3, p-acetylphenylthiourea 4) have been synthesized and characterized by ¹H NMR and IR spectra and elemental analysis. Most of these compounds exhibit wide transparent ranges in the visible region. Their electronic spectra have been studied experimentally, and theoretically by ZINDO/S calculation. The MOPAC software package has been used to evaluate their first-order molecular hyperpolarizabilities (β). All β values of the four coordination compounds are greater than or equal to those of p-nitroaniline, and are larger than β values of their corresponding substituted phenthylthiourea ligands.     

Halochrome Molekeln. 5. Mitteilung. Synthese substituierter 6H-Chromeno[4,3-b]indolizine und ihrer Aza-analogen

Halochromic Molecules. Synthesis of Substituted 6H-Chromeno[4,3-b]indolizines and their Aza-analogues We have synthesized a series of substituted chromeno[4,3-b]indolizines and their respective aza-analogues. Dyes generated from them contain the electrondonating 2-(2-hydroxy-5-methylphenyl)indolizin-3-yl moiety. The 90 MHz FT ¹H-NMR spectra of starting and final products supported the postulated structures. Fragmentations in the mass spectra also were consistent with the assumed structures.     

Electron-impact studies. LXXXIV—Substituent effects in the negative ion mass spectra of aryl esters

Linear plots may be obtained for the fragmentations of aryl p-cyanobenzoates using the McLafferty approach, but the correlations are not as satisfactory as those observed¹ for aryl nitrobenzoates. Some satisfactory correlations of substituent effects are noted in the negative ion spectra of substituted benzyl-p-nitrobenzoates and substituted phenyl-(p-nitrophenyl)acetates. Pronounced rearrangement peaks are observed in the spectra of substituted phenyl-(p-nitrophenyl)acetates. Appearance potential studies suggest that the similarities in ρ values obtained¹ for the fragmentations of aryl m- and p-nitrobenzoate molecular anions are probably due to the correspondence between Hammett σ values and appearance potentials in the two series.     

Mass spectra of some 2-(o-and p-R1-phenyl)-indole-3-carboxaldehyde derivatives. III

The mass spectra of sixteen substituted 2-(o- and p-R¹-phenyl)indole-3-carboxaldehydes which have potentially useful pharmacological properties are presented.     

Stereochemical effects in the electron impact mass spectra of cis-trans isomeric 1,2,3,4-tetramethylcyclohexanes

The mass spectra of six cis-trans isomeric 1,2,3,4-tetramethylcyclohexanes are discussed. The intensity ratio of [M? CH₃]⁺/[M? C₂H₅]⁺ correlates with the strain energies of the stereoisomers. Therefore, the identification of cis-trans isomers is possible by means of their mass spectra. The mass spectra of deuterium labelled compounds demonstrate favoured fragmentation of the axial methyl groups and ring opening between the cis substituted carbon atoms of the cyclohexane.     

Formation of doubly charged ions in field ionization mass spectra of para substituted acetophenones

The doubly charged [M]²⁺, [M+1]²⁺ and [M-O]²⁺ ions are observed in the field ionization mass spectra of para substituted acetophenones. The effect of the type of the substituent on the formation of the doubly charged ions is described.     

Chemical ionization mass spectra of mononitroarenes

The H₂ and CH₄ chemical ionization mass spectra of a selection of substituted nitrobenzenes have been determined. It is shown that reduction of the nitro group to the amine is favoured by high source temperatures and the presence of water in the ion source. The H₂ chemical ionization mass spectra are much more useful for distinguishing between isomeric compounds than the CH₄ CI mass spectra because of the more extensive fragmentation. For ortho substituents bearing a labile hydrogen abundant [MH ? H₂O]⁺ fragments are observed. When the substituent is electron-releasing both ortho and para substituted nitrobenzenes show abundant [MH? OH]⁺ fragment ions while meta substituted compounds show abundant loss of NO and NO₂ from [MH]⁺. The latter fragmentation is interpreted in terms of protonation para to the substituent or ortho to the vitro function, while the first two fragmentation routes arise from protonation at the nitro group. When the substituent is electron-attracting the chemical ionization mass spectra of isomers are very similar except for the H₂O loss reaction for ortho compounds.     

1H- und 13C-NMR-untersuchungen an dibromoxabicyclo[n.2.1]alkanen

The ¹H n.m.r. spectra of some dibromooxabicyclo[n.2.1]alkanes are discussed for the determination of the configuration and conformation. The ¹³C n.m.r. spectra confirm the observed stereochemistry. With increasing ring size the ¹³C n.m.r. chemical shifts of the hetero atom substituted C-atoms C-1 and C-2 move steadily to lower fields.     

Studies in sulphur heterocyles. 2—The 13C NMR spectra of thienocoumarins

¹³C NMR spectra of 3- substituted thieno[2,3-h][1]benzopyran-2-ones and 8-substituted thieno[3,2-f]-[1]benzopyran-7-ones are reported and the substituent dependence of certain ¹³C chemical shifts is noted.     

Synthesis,Pharmacological, and Biological Screening of Novel Derivatives of Benzodiazepines

A series of novel 4‐(substituted phenyl)‐2‐(thiophen‐2‐yl)‐2,3‐dihydro‐1H‐benzo[b][1,4]diazepine have been synthesized from 3‐(substituted phenyl)‐1‐(thiophen‐2‐yl)prop‐2‐en‐1‐one. 3‐(Substituted phenyl)‐1‐(thiophen‐2‐yl)prop‐2‐en‐1‐one was prepared by condensing 2‐acetyl thiophene with various aromatic aldehydes in the presence of 20% NaOH as base. Different 3‐(substituted phenyl)‐1‐(thiophen‐2‐yl)prop‐2‐en‐1‐one on cyclization with o‐phenylenediamine in the presence of NaOH as base resulted in 4‐(substituted phenyl)‐2‐(thiophen‐2‐yl)‐2,3‐dihydro‐1H‐benzo[b][1,4]diazepine derivatives. The structures of synthesized compounds are confirmed by IR, ¹H NMR, mass spectra, and elemental analysis. All the compounds have been screened for their antimicrobial, analgesic, and anti‐inflammatory activities.     

An Efficient Synthesis of Highly Optically Active 4-Substituted-2（5H）-furanones from Chiral 3-Bromo-2（5H）-furanone

Highly optically active 4-substituted-2(5H)-furanones 6a-6j were obtained in good yields with de≥98% by the tandem Michael addition/elimination reaction of chiral 3-bromo-2(SH)-furanone (4a), which was conveniently prepared starting from 2-furaldehyde under mild conditions. The products were identified on the basis of their satisfactory elemental analysis and spectroscopic data of IR, UV, ^1H NMR, ^13C NMR and mass spectra. The stereochemistry and absolute configuration of this type of compounds were established by the X-ray crystallographic study. The reaction provided a short and efficient synthesis of the interesting highly optically active 4-subsdtuted-2(5H)-furanones containing an active pyrimidine and a purine base group.     

Spectroscopic elucidation of pseudo-base formation from benzo[8,9]quinoliziono[4,5,6,7-fed]phenanthrindyliums

¹³C and ¹H NMR spectra and UV spectra are recorded and assigned for a variety of substituted and hetero derivatives of benzo[8,9]quinolizino[4,5,6,7-fed]phenanthrindyliums. Large specific effects of traces of water on these spectra are traced to pseudo-base formation.     

The 1H, 13C and 31P NMR spectra of EZ pairs of some phosphorus substituted alkenes

The olefins Ph₂P(X)CH?CHR [X=lone pair, O, S, Ch₃I; R?Ch₃, ph, P(X)ph₂] have been prepared and their ¹H, ¹³C and ³¹P NMR spectra measured. trans ³J[P(IV)C] (range 18.3–25.7 Hz) is greater than cis ³J[P(IV)C] (range 6.9–11 Hz) but this relationship does not hold for P(III) compounds. In the ³¹P spectra the E isomer absorbs to higher field than the Z isomer for P(III) and P(IV) compounds. The ¹H data are in accord with previous results; average substituent shielding coefficients for ph₂P(X) substituted alkenes are reported.     

The Diels-Alder reaction between substituted 6,6-dimethyl-2-vinylnorpinenes and maleic anhydride

Cycloaddition of substituted 6,6-dimethyl-2-vinylnorpinenes with maleic anhydride occursvia the attack of a dienophile on diene from the less hindered side of the bicyclic fragment. IR, UV, CD, and¹H NMR spectra of adducts have been studied.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1546–1548, August, 1995.The authors are grateful to I. E. Ismaev for recording several¹H NMR spectra.     

Synthesis of 1‐[(1R)‐1‐(6‐fluoro‐1,3‐benzothiazol‐2‐yl)ethyl]‐3‐substituted phenyl ureas and their inhibition activity to acetylcholinesterase and butyrylcholinesterase

A series of novel 1‐[(1R)‐1‐(6‐fluoro‐1,3‐benzothiazol‐2‐yl)ethyl]‐3‐substituted phenyl ureas were synthesized by the condensation of (1R)‐1‐(6‐fluoro‐1,3‐benzothiazol‐2‐yl)ethanamine with substituted phenyl isocyanates under mild conditions. Their structures were confirmed ¹H, ¹³C, and ¹⁹F NMR spectra, and elemental analyses. The optical activities were confirmed by optical rotation measurements. The inhibition activity of 1‐[(1R)‐1‐(6‐fluoro‐1,3‐benzothiazol‐2‐yl)ethyl]‐3‐substituted phenyl ureas to acetylcholinesterase (ACHE) and butyrylcholinesterase (BCHE) was also tested. Preliminary bioassay indicated that the target ureas displayed excellent acetylcholinesterase and butyrylcholinesterase inhibition activity. J. Heterocyclic Chem., 2011.     

Monoamine oxidase and succinate dehydrogenase inhibitory properties of substituted 1,3,4-oxadiazole-2-thiones

Fifteen new 3-arylaminomethyl-5-(2-hydroxy-3,5-dibromophenyl)-1,3,4-oxadiazole-2-thiones were synthesized and characterized by their sharp melting points, elemental analyses and ir spectra. These substituted oxadiazolylthiones were evaluated for their enzyme inhibitory activity. All compounds inhibited in vitro monoamine oxidase and succinate dehydrogenase activity of rat brain homogenates. The degree of monoamine oxidase inhibition ranged from 59-93% at a final concentration of 1 × 10^?4 M whereas the inhibition of succinate dehydrogenase was 49-100% at a final concentration of 5 × 10^?5 M.     

13C NMR spectra of alkyl- and phenylpyrazines and their N-oxides

The ¹³C chemical shifts of 37 pyrazines, including their N-oxides, are reported. Substituent effects of methyl, phenyl and N-oxide groups on the chemical shifts were examined. To comprehend these effects, the chemical shifts were compared with charge densities calculated by the CNDO/2 method and a good correlation was obtained. ¹³C, ¹H coupling constants of some pyrazines were also determined and assigned. These data enable us to assign the ¹³C NMR spectra of substituted pyrazines and to understand the effects of N-oxidation on the pyrazine nuclei.     

Mass spectra of some 2-(o-R1-phenyl)-indole-3-carboxaldehyde derivatives. II

The electron impact mass spectra of thirteen new substituted 2-(o-R¹-phenyl)-indole-3-carboxaldehydes which have potentially useful pharmacological properties, ate presented.     

具有除草活性的吡唑啉并四嗪酮衍生物的设计、合成与定量构效关系的研究

设计合成了一系列未见文献报道的4-乙氧羰基-1,7-二氢-1-取代苯基-5-(未)取代吡唑啉[5,1-d][1,2,3,5]四嗪-7-酮衍生物, 其结构均经过¹H NMR、IR和元素分析表征. 生测结果显示, 与已报道的化合物相比, 它们表现出较好的除草活性. 定量的结构与活性关系研究表明, 它们的除草活性与取代基的立体效应参数和疏水性参数呈现很好的相关性, 相关系数r大于0.8. 当作用对象为油菜时, 化合物的活性可能主要与取代基R¹的摩尔分子折射和取代基R²的疏水性参数有关. 当取代基R¹的摩尔分子折射参数为1.452时, 相应化合物可能具有对油菜最高的除草活性; 当作用对象为稗草时, 化合物的活性主要与取代基R²疏水性参数和Taft (Es)参数有关.