Sequence distribution of 1,4 and 3,4 units in polyisoprenes

The ¹³C-NMR spectra of hydrogenated polyisoprenes were investigated. Polyisoprenes containing various ratios of 1,4 and 3,4 units were prepared with n-BuLi/Et₂O and were hydrogenated by using p-toluenesulfonylhydrazide. ¹³C-NMR signals of the hydrogenated polymers were assigned for the triad sequences arising respectively from the 1, 4 and 3, 4 units of polyisoprenes. On the basis of these assignments it was confirmed that 1,4 and 3,4 units were randomly distributed in the polyisoprenes prepared with n-BuLi and that these polymers did not contain appreciable amounts of head-to-head or tail-to-tail 1,4 linkages.     

13C-NMR.-Substituenteninkremente der N3-Gruppe in Azido-1,4-benzochinonen

¹³C-NMR. Substituent Increments of the Azido-group in 1,4-Benzoquinones The empirical substituent increments of the azido-group in 1,4-benzoquinones have been derived from the ¹³C-NMR. chemical shifts of 2-azido-5-chloro-1,4-benzoquinone. The validity of the obtained values was tested by comparison of the empirical and computed ¹³C-NMR. chemical shifts of other azido-chloro-1,4-benzoquinones.     

Synthesis and ring-opening polymerization of new 1,4-anhydro-glucopyranose derivatives

Three new 1,4-anhydro-glucopyranose derivatives having different hydroxyl protective groups such as 1,4-anhydro-2,3,6-tri-O-methyl-α-D -glucopyranose (AMGLU), 1,4-anhydro-6-O-benzyl-2,3-di-O-methyl-α-D -glucopyranose (A6BMG), and 1,4-anhydro-2,3-di-O-methyl-6-O-trityl-α-D -glucopyranose (A6TMG) were synthesized from methyl α-D -glucopyranoside in good yields. Their polymerizability was compared with that of 1,4-anhydro-2,3,6-tri-O-benzyl-α-D -glucopyranose (ABGLU) reported previously. The trimethylated monomer, AMGLU, was polymerized by a PF₅ catalyst to give 1,5-α-furanosidic polymer having number-average molecular weights (M̄_n) in the range of 2.8 × 10³ to 6.8 × 10³. The ¹³C-NMR spectrum was compared with that of methylated amylose and cellulose. Other anhydro monomers, A6BMG and A6TMG, gave the corresponding 1,5-α furanosidic polymers having M̄_n = 17.1 × 10³ and 1.8 × 10³, respectively. Thus, the substituents at the C2 and C6 positions were found to play an important role for the ring-opening polymerizability of the 1,4-anhydro-glucose monomers. In addition, debenzylation of the tribenzylated polymer gave free (1 → 5)-α-D -glucofuranan. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 841–850, 1998     

~(13)C-NMR STUDY ON THE EQUIBINARY (cis-1,4;1,2) POLYBUTADIENE POLYMERIZED WITH IRON CATALYST

The (cis-1,4 and 1,2) polybutadiene polymerized with iron catalyst was investigated by ~(13)C-NMR. Assignments have been made on the spectra for all peaks of the aliphatic and olefinic carbons using chemical shift corrective terms together with Furukawa parameters. The relative intensities of peaks were calculated from the Bernoulli distribution of cis-1,4 and 1,2 units.Quantification of cis-1,4 and 1,2 contents, sequence distribution, alternation pattern of cis-1,4 and 1,2 units, and the chain propagation mechanism were discussed as a result of the detailed study of the spectra.     

Synthesis of difunctional 1,4-dimethyl-1,4-disilacyclohexanes

Transformations of HVinSiCl₂, HVinSi(Me)Cl, HVinSi(Me)Ph, and HVinSi(Me)NEt₂ in the presence of Pt catalyst were studied. In dilute solutions, the reaction gave a mixture of structural and stereoisomers of five- and six-membered disilacyclanes, resulting from intramolecular cyclization of the initially formed linear dimer. In the case of methyl(phenyl)disilacyclane, the structural isomers were separated andtrans-1,4-dimethyl-1,4-diphenyl-1,4-disilacyclohexane was isolated. The reaction of this product with HCl in the presence of AlCl₃ followed by hydrolysis resulted in the synthesis oftrans-1,4-dichloro- andtrans-1,4-dihydroxy-1,4-dimethyl-1,4-disilacyclohexanes. The structures of the structural and stereoisomers synthesized were confirmed by¹H,¹³C, and²⁹Si NMR and IR spectroscopies and mass spectrometry. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1734–1738, September, 1999.     

Singlet oxygenation of 1,2-poly(1,4-hexadiene)s

The microstructural changes that occur in cis and trans forms of 1,2-poly(1,4-hexadiene) during methylene blue-photosensitized oxidation were examined by infrared (IR) and ¹³C-NMR spec-troscopy. The singlet oxygenation of these polymers yielded the expected allylic hydroperoxides accompanied by double bond shifts to new vinyl and trans-vinylene double bonds. The photosensitized oxidation exhibited zero-order kinetics; the relative rates for the cis- and trans-1,2-poly(1,4-hexadiene)s were approximately 3.8:1.0.     

Quantitative estimation of trans-1,4 and cis-1,4 isomers in polychloroprene by high-resolution NMR

In the ¹H-NMR spectrum of polychloroprene dissolved in C₆D₆, the ?CH proton signal was separated into two triplet peaks. These triplet signals were assigned to the ?CH proton in the trans-1,4 and cis-1,4 isomers by measurement of ¹H-NMR spectra of 3-chloro-1-butene and a mixture of trans- and cis-2-chloro-2-butene as model compounds for the 1,2, trans-1,4 and cis-1,4 isomers. In ¹H-NMR spectra (220 Mcps) of polychloroprene dissolved in C₆D₆, two triplet signals were separated completely from which the relative concentrations of trans-1,4 and cis-1,4 isomers could be obtained quantitatively.     

13C-NMR-spektroskopie chinoider verbindungen—II: Substituierte 1,4-naphthochinone und anthrachinone

Proton coupled and proton noise decoupled ¹³C-NMR spectra of 18 1,4-napthoquinones and 13 anthraquinones with oxygen, nitrogen and halogen substituents have been measured. The assignment of the spectra was largely achieved with the aid of the two- and three-bond spin-spin coupling between ¹³C and protons and the substituent effects.     

13C NMR spectroscopic study of epoxidized 1,4-polyisoprene and 1,4-polybutadiene

Partly epoxidized cis- and trans-1,4-polyisoprenes and cis-and trans-1,4-polybutadienes were prepared, and their ¹³C NMR spectra examined. All the prominent resonances in the spectra of the epoxidized polymers were assigned by using lanthanide shift reagent and off-resonance decoupling experiments. A ¹³C NMR method of quantitative assessment of the epoxide content was developed following determination of relative spin-lattice relaxation time (T₁) and nuclear Overhauser effect (NOE) parameters of the various carbons in the epoxidized polyisoprenes and polybutadienes.     

Efficient and Convenient Synthesis of 1,4-Benzoxazines, 1,4-Benzothiazines,Spiro-1,4-benzoxazines,and Spiro-1,4-benzothiazines

An efficient, convenient synthesis of 1,4-benzoxazines, 1,4-benzothiazines, spiro-1,4-benzoxazines, and spiro-1,4-benzothiazines derivatives was accomplished in good yields via the novel intramolecular cyclization mediated by mild base K₂CO₃ in ethanol solvent. A variety of substrates can participate in the process with good yields, making this methodology have broad applicability. All the structures of synthesized compound have been confirmed by spectral analysis.

Supplemental materials are available for this article. Go to the publisher's online edition of Synthetic Communications ^® to view the free supplemental file.     

Microstructure par RMN-13C de terpolymeres ethylene-propylene-hexadiene-1,4

¹³C-NMR spectra (62.89 MHz) of ethylene-propylene-1,4-hexadiene terpolymers have been studied. Five resonances can be uniquely assigned to the incorporated diene monomer. Comparison of chemical shifts for model compounds and these five resonances prove that only trans hexadiene is incorporated in the terpolymers.     

A NEW PEAK (T_4) IN THE ~(13)C-NMR SPECTRUM OF POLYBUTADIENE

A new peak at 39.0 ppm in the ~(13)C-NMR spectrum of polybutadiene (PBD) was discovered. This peak is assigned to the fourth peak (T_4) of trans-1,4-sequence marked with an asterisk as shown in Fig. 3 in the text.The occurrence of T_4 carbon nuclei is strongly affected by their neighboring 1,2-units. So long as both contents of trans-1,4- and 1,2-units attain their proper amounts the peak (T_4) with appear in the ~(13)C-NMR spectrum of PBD.     

Study of molecular motions and 14N quadrupolar coupling in 1,3- and 1,4- diethylpyridinium bromides using 13C and 14N relaxation time measurements

The internal and overall motions of 1,3- and 1,4-diethylpyridinium bromides have been studied by ¹³C relaxation. The enthalpies of activation for the rotation of the ethyl groups in positions 1 and 3 are deduced from the temperature dependence of the T₁ values of the methylene and methine carbons. The ¹⁴N quadrupolar relaxation time, T_q, together with ¹³C relaxation data provide an estimate of the ¹⁴N quadrupolar coupling constants.     

Synthesis and properties of poly(cis-1,4-dihydroxy-2,3-epoxybutane)

The cyclic acetone ketal of 1,4-dihydroxy-2,3-epoxybutane (DMTO) polymerizes with i-Bu₃Al-0.7 H₂O catalyst by a cationic mechanism at ?78°C to a moderate molecular weight (η_inh up to 0.7), atactic (based on ¹³C-NMR) polymer (PDMTO). At higher temperature and in bulk, up to 14% crosslinked polymer is obtained as a result of epoxide and ketal ring opening. Triethylaluminum is an effective catalyst at 0–50°C in bulk. Coordination catalysts were less effective but the results indicate that an effective one can be designed. PDMTO is readily hydrolyzed with aqueous HCl treatment to atactic, water-soluble poly(1,4-dihydroxy-2,3-epoxybutane) (PDHEB) with a T_g of 80°C. PDHEB is melt stable to 200°C and can be molded to give brittle, clear films that readily pick up 5–10% H₂O from the atmosphere to give properties like those of plasticized poly(vinyl chloride). PDHEB is degraded by electron beam radiation but can be crosslinked with glyoxal plus toluene sulfonic acid/The bis(trimethylsilyl) ether of cis-1,4-dihydroxy-2,3-epoxybutane was polymerized cationically with the i-Bu₃Al-0.7 H₂O catalyst at ?78°C to a fairly tactic, presumably racemic di-isotactic, amorphous polymer, with η_inh of 0.16. A mechanism is proposed for this stereoregular polymerization based on a complexation of the Si side group of the last chain unit with the propagating oxonium on.     

1,4-Dihydro-1λ5,4λ5-[1,4]diphosphinine und ein 1,4-Dihydro-1λ3,4λ3-[1,4]diphosphinin

1,4-Dihydro-1λ⁵,4λ⁵-[1,4]diphosphinines and a 1,4-Dihydro-1λ³,4λ³-[1,4]diphosphinine Reaction of thio- or dithiocarbonic acids with ethinyl amino phosphanes leads to 1,4-dihydro-1λ⁵,4λ⁵-[1,4]diphosphinine-1,4-disulfides. By this route compounds 4, 7 , and 8 have been prepared. Desulfurization of 4 with tri-n-butylphosphane results in 1,2,4,5-tetraphenyl-1,4-dihydro-1λ³,4λ³-[1,4]-diphosphinine 5 , which can be oxidized with tert-butyl-peroxide to the corresponding dioxide, 6 . From the reaction mixture of phenyl-phenylethinyl diethylamino phosphane and thioacetamide compound 4 and the unsymmetrical 1,4-dihydro-1λ⁵,4λ⁵-[1,4]diphosphinine 9 were isolated. Properties, nmr, ir and mass spectra of all new products are reported. A mechanism for the formation of 9 is suggested. The results of the X-ray structure determination of 8 and 9 are described.     

The NMR spectra of 1,4-dioxin and 1,4-dithiin partially oriented in a nematic phase

The PMR spectra of 1,4-dioxin and 1,4-dithiin have been studied in nematic phase liquid crystalline solvents. The ratio of the interproton distances r₁₂ and r₁₃ and the CCH angles have been determined.     

Synthesis of nucleoside analogs of 1,4-oxathiane, 1,4-dithiane,and 1,4-dioxane

The two regioisomers 6-chloro-9-(1, 4-oxathian-3-yl)-9H-purine ( 5 ) and 6-chloro-9-(1,4-oxathian-2-yl)-9H-purine ( 6 ) were obtained when 3-acetoxy-1,4-oxathiane ( 3 ) was subjected to the acid-catalyzed fusion procedure; compound 3 was prepared by a Pummerer reaction with 1,4-oxathiane 4-oxide ( 2 ). The nucleoside analog 6 could he converted into the adenine derivative 7 and 9-(1,4-oxathian-2-yl)-9H-purine-6(1H)thione ( 8 ). The following nucleoside analogs have also been synthesized: 6-chloro-9-(1,4-dithian-2-yl)-9H-purine ( 13 ), 9-(1,4-dithian-2-yl)adenine ( 14 ), 9-(1,4-dithian-2-yl)-9H-purine-6(1H)thione ( 15 ), and 6-chloro-9-(1,4-dioxan-2-yl)-9H-purine ( 18 ).     

13C-NMR spectra of cis-polymyrcene and cis-polyfarnesene

Homopolymers of myrcene and farnesene were prepared anionically in pure cyclohexane. The microstructure, determined from an analysis of the ¹³C-NMR spectrum and spin-lattice relaxation times, indicates the polymers are at least 85% cis-1,4, 10% cis-3,4, and under 3% trans-1,4.     

Synthesis and investigation of cytotoxicity of new N- and S,S-substituted-1,4-naphthoquinone (1,4-NQ) derivatives on selected cancer lines

1,4-Naphthoquinones (1,4-NQ) have been reported to possess a variety of pharma-cological properties including antibacterial, antifungal, antiviral, anti-inflammatory, anti-artherosclerotic, and anticancer effects. In this study, new N- and S,S-substituted-1,4-NQ derivatives were synthesized in excellent yields and were completely characterized by spectroscopic analysis IR, NMR (¹H and ¹³C), MS and microanalysis. The cytotoxic activities of 1,4-NQ derivatives were examined against to A-549, DU145, HCT-116 and MDA-MB-231 cancer cells. Among these compounds, 2-[4-(2-furoyl)piperazine-1-yl]-3-chloro-1,4-NQ 5 and 2,3-bis(cyclobuthylsulfanyl)-1,4-NQ 17 were identified as the most potent anticancer agents with cytotoxic activity against three cell lines (breast (MDA-MB-231), prostate (DU145), colorectal (HCT-116).     

Synthesis and carbon-13 nuclear magnetic resonance spectroscopy of 5,6-dihydro-2-methyl-1,4-oxathiin,trans-tetrahydro-1,4-benzoxathiin, 1,4-tetrahydro-[9,10]benzoxathiin,the 4-oxides, 4,4-dioxides and related acyclic compounds

The results of a ¹³C NMR spectral investigation involving 5,6-dihydro-1,4-oxathiins, 1,4-tetrahydro[9,10]benzoxathiin, trans-tetrahydro-1,4-benzoxathiin, and the corresponding sulfoxides and sulfones are reported. An interpretation involving a dipolar structure with (2p→2p)π conjugation as opposed to (2p→3d)π interactions with the vinyloxy sulfides seems consistent with trends in the ¹³C NMR shifts. For the sulfoxides and sulfones, the substitutent-induced chemical shift (SCS) effects at the β vinylic carbons (βSO and βSO₂ effects) are considerably less than those at sp³ carbons. The γSO and γSO₂ values at the sp²γ carbons indicate deshielding, in contrast to the shielding at the sp³ carbons.