PMR spectra ard structure of 3,4- and 2,5-disubstituted sulfolanes

Conclusions Based on studies of the PMR spectra of 3,4- and 2,5-disubstituted sulfolanes it has been shown that the difference in the chemical shifts of the geminal protons and the values of the chemical shifts of the protons associated with substituents are reliable criteria for establishing the configuration of the disubstituted five-membered cyclic compounds.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 5, pp. 1029–1033, May, 1980.The authors would like to thank U. M. Dzhemilev for donating the 2,5-divinylsulfolanes for investigation.     

CIDNP as the proof of a radical mechanism of the reactions of Grignard reagents with diazonium salts

The PMR spectrum recorded during the reaction of tert-butylmagnesium chloride with p-chlorophenyl diazonium tetrafluoborate shows the CIDNP effect in the spectra of the the reaction products. Enhanced absorption and emission (the multiplet effect) has been observed for the protons of the vinyl group of isobutylene and the methyl protons of isobutane. The reaction of these diazonium salts with benzylmagnesium chloride results in only one polarised product, chlorobenzene. Such a polarisation proves the radical mechanism of the reaction which started with one-electron transfer from the Grignard reagent to the diazonium salt.     

PMR spectra of the dioxane lignins of some plants of the family Malvaceae

Analysis of PMR spectra of the dioxane lignins of three species ofAthea, of kenaf, and of the cotton plant has shown that the number of free aromatic protons does not correlate with the number of OCH₃ groups, which indicates different degrees of condensation of the dioxane lignins studied. In all the preparations a very small amount of coumarane structures were found. The aliphatic OH groups have been distinguished as primary (γ-OH) and secondary (α-OH) and their quantitative estimation has been carried out from the PMR spectra.     

Matrix-isolation and electronic structure of vinyl-substituted silylenes and their complexes with bases [1]

Vinyl-substituted silylenes, 2,5-bis(methylene)-1-silacyclopentane-1,1-diyl ( 1 ) and 2-methylene-1-silacyclopentane-1,1-diyl ( 2 ), generated photochemically from the corresponding trisilanes in 3-methylpentane (3-MP) at 77 K, showed broad bands at 505 and 475 nm, respectively, which were assigned to the n(Si)-3p(Si) transition. The origin of the red shift in the n(Si)-3p(Si) transition is ascribed to the significant lowering of the 3p(Si) orbital level caused by the vinyl substitution on the silylene; the relatively high-lying 3p(Si) orbital can interact more effectively with the antibonding π* orbital than with the bonding π orbital of the vinyl group. The absorption spectra for 1 and 2 in the presence of several bases in 3-MP glass matrix shifted significantly to blue due to the formation of the corresponding base complexes. Analysis of the spectral change of the silylenes upon complexation with bases was very constructive for the understanding of the structural characteristics of substituted silylenes.     

Organometallic compounds : XII. stereochemical interconversion reactions between 1,1′−bis(α-hydroxyalkyl)ferrocenes and 7-oxa[3]ferrocenophanes

Meso and racemic isomers of 1,1′-bis(α-hydroxyalkyl)ferrocene derivatives, and trans and cis isomers of 7-oxa[3]ferrocenophanes have been isolated. The configurations of these isomers have been determined both by spectroscopy and from their reaction behavior. It has been found that the ring-closure and ring-opening interconversion reactions between 1,1′-bis(α-hydroxyalkyl)ferrocenes and 7-oxa[3]ferrocenophanes are stereospecific. PMR spectra of the diols and ethers have been examined at 100 MHz in CF₃COOH, and the existence of α-[1′-(α-hydroxyalkyl)ferrocenyl]carbonium ions has been demonstrated in this acid. A mechanism for the various interconversion reactions is proposed on the basis of their stereospecific reactivity and from the PMR spectra of the carbonium ions.     

PMR of complexes of organohalostannanes with N-vinyl-N-ethylimidazole

The chemical shifts and spin-spin coupling constants of the protons of the vinyl and ethyl groups and of the imidazole ring in the PMR spectra of complexes R_4–n·SnX_n · mB, where R=C₂H₅, C₄H₉;X=Cl, Br, I; B is N-vinylimidazole or N-ethylimidazole; and n=1 (m=1) and 2 (m=2), are compared. The electronic and geometrical structures of these complexes are discussed.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 391–394, March, 1973.     

Organo-silanes and -germanes with chelated and/or non-chelated oxinato ligands

Several tri- and di-organo(oxinato)-silanes and -germanes have been prepared from corresponding organo-silazanes or -germazanes. The UV spectra indicate that the compounds involve either chelated or non-chelated oxinato groups or both depending on the number and kind of organic groups on the metal atom. The PMR spectra of RR′Si(OX)₂ (R = alkyl, R′ = vinyl or phenyl) are interpreted in terms of rapid exchanges between the two kinds of oxinato groups     

Synthesis and structure of 1,4-diaryl-7,7-dimethyl-1,2,3,4,5,6,7,8-octahydroquinoline-2,5-diones

Condensation of 5-arylidene-2,2-dimefhyl-1,3-dioxane-4,6-diones with 5,5-dimethyl-3-arylamino-2-cyclohexanones yields 1,4-diaryl-7,7-dimethyl-1,2,3,4,5,6,7,8-octahydroquinoline-2,5-diones. The compounds have been characterized from their IR, UV, and PMR spectra. It has been established that the N-phenyl ring, which projects from the plane of the octahydroquinolinedione ring, has a shielding effect on the magnetic field of the protons at the 7- and 8-positions of the ring in the molecules of the compounds synthesized.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 9, pp. 1227–1232, September, 1993.     

Diastereotopic effect in some N-substituted-3-methyl-4,1-benzoxazepine-2,5-diones

1H NMR assignment of seven differently N-substituted-3-methyl-4,1-benzoxazepine-2,5-diones (I) revealed that with the exception of allyl, N-methylene protons of the substituents exhibit diastereotopy due to presence of a chiral centre in the heterocyclic ring at C-3. The significant finding is that the methylenes at C-2' in the substituents n-propyl and n-butyl (Id, Ie) also show diastereotopy. However, the one closer to the chiral centre (at C-1') exhibits greater non-equivalence of its protons. The diastereotopic methylene groups reported in this study correspond to the simplest system AB on one hand and as complex as ABMM'X2 or ABMM'X3 on the other. Calculated spectra obtained from assigned set of data for most of the coupled protons were in good agreement with the observed ones.     

Lewis acid-catalyzed reactions of donor-acceptor cyclopropanes with furan derivatives

Lewis acid-catalyzed reactions of dialkyl 2-arylcyclopropane-1,1-dicarboxylates with 2,5-dimethylfuran were found to give products of [3+2]-cycloaddition to C(2)-C(3) bond, which contain reactive vinyl ether moiety. These adducts can be further transformed into various products depending on the Lewis acid, the nucleophilicity of aryl group in starting cyclopropane and the ratio of reagents. The vinyl ether moiety can attack the appropriate nucleophilic center in intramolecular or intermolecular mode or can undergo cycloaddition to the second equivalent of donor-acceptor cyclopropane. Alternatively, 2,5-diphenylfuran formed Friedel-Crafts products only when reacted with donor-acceptor cyclopropanes.     

Chirality of exo-heterosubstituted semiquinoid systems

Conclusions The observation of diastereotopism of the methoxy groups (at a distance of eight bonds from the asymmetric center) in the PMR spectra of 4,4-disubstituted l-(dimethylphosphorylmethylidene)-2,5-cyclohexadienes has been used to demonstrate the chirality of para-semiquinoid systems containing a heteroatom in the unsaturated exo-fragment of the molecule and two substituents distinguishable from each other in the geminal position.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 10, pp. 2296–2299, October, 1986.     

PMR-Spektren einiger Alkoxy-9-chlor-6-nitroacridine

The spectra of some 9-chloro-6-nitroacridines with methoxy substituents in position 1,4; 2,4; 3,4; 2,3; and ethoxy substituents in positions 1, 2, 3, were recorded. The influence of electron releasing alkoxy groups and electron withdrawing nitro groups on chemical shifts of protons in the 9-chloroacridinic cycle was discussed and PMR parameters were determined, comparatively with those of acridine and 9-chloroacridine. Good agreement between calculated and experimental values is observed. The spectrum of 9-chloro-1,2,3-triethoxyacridine shows for the four protons of the ringC. (H-5, H-6, H-7, H-8) anAMNX coupling pattern whose parameters were determined.     

NMR spectra of model compounds of poly(vinyl chloride)

The NMR spectra of three stereoisomers of 2,4,6-trichloroheptane as model compounds of poly(vinyl chloride) have been studied. Spectra were observed at 60 and 100 Mc./sec., both at room temperature and at high temperatures. A spin-decoupling experiment was performed. Computational analysis of the spectra was carried out on an IBM 7090 computer. The difference of the chemical shifts of the two meso methylene protons at 60 Mc./sec. was found to be ca. 7 cps. for the isotactic three-unit model while it was ca. 16 cps. for the isotactic two-unit model or heterotactic three-unit model. The spectra of poly(vinyl chloride) were interpreted reasonably on the basis of this result. Observed values of vicinal coupling constants of model compounds were interpreted as the weighted means of those for several conformations, and the stable conformations of the models were determined.     

An NMR study of some substituted 1,3- and 1,4-bistrifluoromethylbenzenes

Contrary to an earlier report, the metallation of 1,3-bistrifluoromethylbenzene with n-butyllithium is found to take place at the 4- and 2-positions. Lithiation of 1,4-bistrifluoromethylbenzene and subsequent carboxylation gives exclusively the 2-carboxylic acid. Structures are assigned on the basis of PMR data (100 and 220 MHz). The effects of coupling between aromatic protons and trifluoromethyl groups and the aromatic chemical shifts brought about by esterification are discussed for a series of bistrifluoromethylbenzoic acids.     

Synthesis of Poly（p-phenyleneethynylene）s with Crosslinkable End or Side Groups and Its Solid State Structure and Optical Properties Before and after Crosslinking

Two crosslinkable poly(p-phenyleneethynylene)s(PPEs): poly[2,5-di(2'-ethyl-hexyloxy)-1,4-phenylenee-thynylene] with end-capped vinyl(PPE1) and poly[2,5-di(allyloxy)-1,4-phenyleneethynylene-2,5-di(2'-ethyl-hexyloxy)-1,4-phenyleneethynylene](PPE2) were synthesized. Via the thermal addition reactions of vinyl end groups of PPE1 and allyloxy side groups of PPE2, crosslinked polymers C-PPE1 and C-PPE2 were obtained, respectively. The two polymers were characterized by wide-angle X-ray diffraction(WXRD), ultravio...     

Laser desorption/fourier transform mass spectra of poly(phenylene sulfide), polyaniline,poly(vinyl phenol), polypyrene,and related oligomers: Evidence for carbon clusters and feasibility of physical dimension measurement

Laser desorption/Fourier transform mass spectra of poly(phenylene sulfide), polyaniline, poly(vinyl phenol), polypyrene, poly(p-phenylene), poly(1-methyl-2,5-pyrrolylene), poly(1-phenyl-2,5-pyrrolylene), and poly(2,5-thienylene) are compared. Poly(phenylene sulfide) fragments at C? S bonds during analysis, but rearrangement is minor. Evidence is found for dibenzothiophene moieties within the polymer chains. Unambiguous determination of the structure of polyaniline is not possible. Rearrangement appears to accompany chain scission. Completely aromatic polymers do not undergo similar reactions during analysis. Species with more carbons than can be accounted for by an integer multiple of six-membered rings arise from side reactions during dehydrocoupling of aromatic monomers. Carbon clusters, which are observed in the spectra of some aromatic polymers, appear to arise from laser volatilization and multiphoton ionization of large polynuclear components that are formed during synthesis. Negative ions of about 40–120 carbons and positive ions with about 120–400 atoms are detected. The results also suggest that the physical dimensions of some polymer molecules might be measured by Fourier transform mass spectrometry.     

Properties and separation method of enantiomers of the mono- and bis-substituted derivatives of 3,3′,4,4′-tetramethyl-1,1′-diphosphaferrocene: structural analysis using X-ray diffraction and circular dichroism

This work expands on the recent separation of the enantiomers of the C₂-symmetrical bis-substituted derivatives of 1,1′-diphosphaferrocene. The effective separation of mono-substituted 1,1′-diphosphaferrocenes by the proposed method is demonstrated. The absolute configuration of the three separated components was established using X-ray diffraction. Circular dichroism spectra were collected for all of the separated compounds. The spectrum of each compound shows a characteristic curve, and the curves for the enantiomers are symmetrical. We also show that the correct absolute configuration for similar species can be assigned on the basis of the obtained data. We propose an explanation for the abnormal ¹H NMR spectra of phospholyl protons in some derivatives of 1,1′-diphosphaferrocene. A density functional theory (DFT) study of the conformation, as well as circular dichroism and NMR spectra of the chosen species, is also presented.     

Investigation of the structure of substituted 3H, 6H-6-sila-3-azaaceanthrylenes by PMR spectroscopy

The structure of substituted 3H,6H-6-sila-3-azaaceanthrylenes was confirmed as a result of an analysis of the PMR spectra and by the spectra at 360 MHz. Computer analysis of the ABCD spectrum of the phenylene protons demonstrated the characteristic nature of the spin-spin coupling constants (SSCC) in the indicated series.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1347–1350, October, 1982.     

Conformational properties of the 2′- and 3′-hydroxy groups of 5′-O-trityluridine

The results of a study of the temperature dependence of the SSCCs of the hydroxyl protons in the PMR spectra of 5′-O-trityluridine indicate the existence of an intramolecular bond between the 2-keto oxygen of the base and the 2′-hydroxyl in deuterochloroform. Under these conditions, stabilization of the 3′-endo (N) conformation of the ribose ring is observed. The existence of the influence of the temperature on the population of the 3′-hydroxyl rotamers shows the formation of a hydrogen bond between OH-3′ and O-2′. In polar solvents free rotation of the hydroxy groups is observed.     

Synthesis and configuration of diastereomeric 2,4-, 2,5-, and 2,6-piperidinedicarboxylic acids and their dimethyl esters

The reduction in an acidic medium over a platinum catalysts of 2,4-, 2,5-, and 2.6-pyridinedicarboxylic acids gave cis-2,4-, -2,5-, and -2,6-piperidinedicarboxylic acids, heating of which in an alkaline medium led to thermodynamically equilibrium mixtures of diastereomers. Individual trans-2,5-piperidinecarboxylic acid was isolated. The configurations of the 2,4-, 2,5-, and 2,6-piperidinedicarboxylic acids and their methyl esters were established by means of the PMR spectra.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 367–371, March, 1985.