Study of specific C-H...N intramolecular interactions in heteroaryl vinyl ethers,on the basis of factor analysis of1H and13C NMR spectral parameters

On the basis of a factor analysis of the¹H and¹³C NMR spectral parameters of the vinyloxy group in a broad series of aryl and heteroaryl vinyl ethers, it has been established that these parameters change mainly under the influence of the electronic effect of the aromatic fragment and specific C-H...N intramolecular interaction of the -hydrogen atoms of the vinyl group with an endocyclic nitrogen atom. It has been shown that the parameters most sensitive to the specific C-H...N. interaction are the chemical shifts of the -proton and -carbon of the vinyl group, and also the spin-spin coupling constant between these atoms.Translated from Izvestiya Akademii Nauk SSSR, No. 10, pp. 2289–2297, October, 1991.     

13C chemical shifts of the β olefinic carbon in some heterocyclic vinyl ethers as a measure of p-π conjugation

¹³C NMR spectra of 5- and 6-membered heterocyclic vinyl ethers containing an endocyclic or exocyclic CC bond have been determined and the chemical shift of the β carbon of the vinyl group has been used as a measure of the extent of p-π conjugation in the vinyloxy system. The results show that in the 6-membered heterocyclic vinyl ethers with an exocyclic double bond, such as 2-methylenetetrahydropyran, p-π conjugation is essentially weaker than in the corresponding 5-membered heterocycles, such as 2- methylenetetrahydrofuran. In the respective endocyclic isomers, the difference in the extent of conjugation is considerably smaller, although the same relative order still applies. The spatial structures of these compounds are discussed on the basis of these findings.     

Structure of vinyl ethers of a number of azoles according to1H and13C NMR data and quantum-chemical calculations

NMR¹H and¹³C spectra have been used to establish the conformational states of a number of azole vinyl ethers and to study the nature of the conjugation of the unshared pair of electrons of the oxygen atom with the azole and vinyl moieties. The H¹ NMR spectra of the vinyl ethers of indazole, 4,5-diphenylimidazole, benzimidazole, and 1,2,4-triazole revealed anomalous downfield shifts of the signal of the proton of the vinyl group, which are attributed to specific interactions, resembling weak hydrogen bonds, between these hydrogen atoms and the pyridine nitrogen. This conclusion agrees with the results of quantum-chemical calculations for the vinyl ether of indazole.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 5, pp. 1031–1036, May, 1990.     

9-alkenylcarbazoles

The¹H and¹³C NMR spectra of 9-vinylcarbazole and its 3-chloro, 3,6-dichloro, and 3-nitro derivatives were recorded and studied. It is shown that electron-acceptor substituents reduce the shielding of the -carbon atom and the trans proton of the vinyl group. A good linear correlation between the chemical shifts of these nuclei and the Hammett _para ^– constants with the values (3.78 for¹³C and 0.28 for¹H_trans) is observed. It was established by comparison of the results with the¹H and¹³C NMR spectral parameters for some of the vinyl compounds that the degree of conjugation of the p electrons of nitrogen with the electrons of the double bond in 9-vinylcarbazoles is lower than in simple vinyl and vinyl phenyl ethers and vinyl acetate.See [25] for communication I.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1368–1371, October, 1976.     

Reaction of the vinyl ethers of heterocyclic imino alcohols with acyl halides

Conclusions The reaction of the vinyl ethers of heterocyclic imino alcohols with acyl halides gave a number of new vinyl ethers of heterocyclic amido alcohols as 11 mixtures of the isomeric 3,6- and 5,6-dihydropyrans, and ³- and ⁴-piperidines.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 11, pp. 2538–2541, November, 1980.     

Relative thermodynamic stabilities of allyl vinyl and propenyl vinyl ethers

The relative thermodynamic stabilities of a number of isomeric allyl vinyl and propenyl vinyl ethers were determined by chemical equilibration in DMSO solution with KOBu-t as catalyst. From the temperature dependence of the values of the equilibrium constant the parameters G _m , H _m and S _m of isomerization at 298.15 K were evaluated. Propenyl vinyl ethers, owing to their low enthalpy contents, are much more stable than the isomeric allyl vinyl ethers. It appears that in the parent propenyl vinyl ether, the Me group attached to C- of the divinyl ether skeleton has a strong stabilizing effect, comparable to that of alkyl groups in ordinary olefins, on the unsaturated system. In more heavily alkyl-substituted divinyl ethers, however, the stabilizing effects of alkyl groups are less prominent, being comparable to the low stabilization energies of alkyl groups in vinyl ethers, and depend moreover, on the pattern of substitution.     

Vinyl Ethers Containing an Epoxy Group: XXI. Synthesis and Acid-Catalyzed Cyclization of 1-[ω-(Vinyloxy)alkoxy]-3-(2-propynyloxy)-2-propanols- A Simple Route to 2-Propynyloxymethyl-Substituted Cyclic Polyethers

Base-catalyzed reaction of 2-[-(vinyloxy)alkoxy]methyloxiranes with 2-propynyl alcohol (3 wt % of t-BuOK, 60-85°C, 3-12 h) afforded first reperesentatives of the 1-[-(vinyloxy)alkoxy]-3-(2-propynyloxy)-2-propanol series in up to 99% yield. Treatment of 1-[2-(vinyloxy)ethoxy]- and 1-[2-(vinyloxy)ethoxyethoxy]-3-(2-propynyloxy)-2-propanols with trifluoroacetic acid (0.5 wt. %) in dry diethyl ether resulted in cyclization with formation of up to 96% of (2-methyl-1,3,6-trioxocan-4-yl)methyl- and (2-methyl-1,3,6,9-tetraoxacycloundecan-4-yl)methyl 2-propynyl ethers.     

Effect of central spacer chain structure on cationic cyclopolymerization tendency of divinyl ethers

To clarify the effects of the central spacer chain structure of divinyl ethers on their cationic cyclopolymerization tendencies, 1,4‐bis[(2‐vinyloxy)ethoxy]benzene ( 1 ), 1,4‐bis[(2‐vinyloxy)ethoxy]butane ( 2 ), 1,6‐bis[(2‐vinyloxy)ethoxy]hexane ( 3 ), 1,8‐bis[(2‐vinyloxy)ethoxy]octane ( 4 ), and 1,4‐bis[(4‐vinyloxy)butoxy]butane ( 5 ) were polymerized with the hydrogen chloride/zinc chloride (HCl/ZnCl₂) initiating system in methylene chloride (CH₂Cl₂) at 0 °C at low initial monomer concentration ([M]₀ = 0.15 M). The polymerizations of divinyl ethers 2 and 3 gave soluble polymers quantitatively. In contrast, the polymerizations of divinyl ethers 1 , 4 , and 5 underwent gel formation at high monomer conversion. The content of the unreacted vinyl groups of the obtained soluble polymers was measured by ¹H NMR spectroscopy. Judging from the relatively low vinyl contents of the polymers produced even in the early stage of the polymerization (monomer conversion < ～20%), the cyclopolymerization occurred to some extent for 2 , 3 , and 4 . On the contrary, the polymers produced from 1 and 5 exhibited the relatively high vinyl content, indicating that the cyclopolymerization tendencies of 1 and 5 were lower than those of 2 , 3 , and 4 . These results are discussed in terms of the structural variety of the spacer chains: (1) the presence of benzene ring ( 1 vs 2 ), (2) their length ( 2 vs 3 and 4 ), and (3) the position of ether oxygen ( 4 vs 5 ). © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 4002–4012, 2002     

Calculation of the torsional angles in alkyl vinyl ethers from the direct13C-1H spin-spin interaction constants

It is shown that the differences in the direct¹³C-¹H SSIC of the C atom of the vinyl groups in alkyl vinyl ethers depend on the value of the torsional angle about the C bond. This dependence is used to make quantitative estimates of the torsional angles in alkyl vinyl ethers with alkyl substituents ranging from CH₃ to t-C₄H₉ Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 2, pp. 390–393, February, 1991.The authors are grateful to S. V. Kirpichenko for providing the triethylvinylthiosilane, synthesized as described in [11].     

Furfuryl vinyl ethers in [4+2]-cycloaddition reactions

For the first time [4+2]-cycloaddition reactions were carried out between furfuryl vinyl ethers and typical dienophiles and heterodienes proceeding in uncatalyzed conditions and resulting in previously unknown heterocyclic systems containing either free vinyloxy groups or furfuryl substituents. With maleic anhydride and maleimide furfuryl vinyl ethers afforded 1-(vinyloxyalkyl)tricyclodec-8-ene-3,5-diones in up to 72% yields, and with N-benzylideneaniline or acrolein the corresponding functionally substituted tetrahydroquinolines (yield up to 65%) or 3,4-dihydropyrans (yield 23–50%) were obtained.     

F and C spectra of fluorinated and partially fluorinated vinyl alkyl ethers

Fluorine, hydrogen, and ¹³C NMR spectral data have been obtained for vinyl alkyl ethers containing fluorines. Some of the molecules are perfluorinated and others include hydrogen, bromine, and chlorine substituents. New generalizations regarding FF spin-spin coupling are developed and used, along with previously recognized correlations, in the confirmation of structures and the assignments of resonances. ¹³C spectroscopy, especially the analysis of ¹³C¹⁹F coupling, is critical in several of the structure determinations. Chlorine isotope effects on fluorine chemical shifts are observed when the chlorine and fluorine are attached to the same carbon, and are also used in the structure analyses. Long-range couplings between fluorines in the vinyl group and fluorines in the alkyl group are interpreted in terms of molecular geometry which allows certain of the alkyl fluorines to “touch” the fluorines cis and gem to the ether oxygen but not the fluorine trans to the oxygen. Two bond ¹³C¹⁹F coupling across the vinyl double bond is found to vary dramatically with the electronegativity of the vinyl substituents in the ethers, in accordance with previous observations for olefins.     

Intramolecular interactions in vinyloxyquinolines

The UV spectra of 2-, 3-, 4-, 6-, and 8-vinyloxyquinolines were obtained, and their structures were subjected to quantum-chemical calculation within the Pariser-Parr-Pople (PPP) -electron approximation in order to ascertain the effect of the vinyloxy group on the nature of their electron transitions and on their electronic structures. A linear relationship between the difference in the charges on the carbon atoms of the vinyl group and its integral intensity in the IR spectra was established. As a result it was concluded that there is an analogy between the orienting effect of the suhstituents in benzenes and the interaction of the vinyloxy group with the nitrogen atom in vinyloxyquinolines. The polarity of the vinyl group in vinyloxyquinoline hydrochlorides was estimated on the basis of the established dependence.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 12, pp. 1662–1665, December, 1977.     

Rotational isomerism of vinyl ethers of azines based on the data of IR spectroscopy and quantum-chemical AM1 calculations

The IR spectra of vinyl ethers of azines have two C=C stretching vibration bands of the vinyl group at 1620 and 1640 cm⁻¹, which correspond to thes-cis and nonplanars-trans conformers, respectively. According to the results of AM1 calculations, the hetaryl fragment and the vinyl group in thes-trans conformers of all the ethers under study are twisted out of the C−O−C plane by ∼30°. In thes-cis conformation, the angle of rotation of the heterocycle with respect to the vinyloxy group varies from 45 to 90°. The character of the change in the intensity of the v(C=C) absorption bands of the doublet under changes of the temperature indicates that thes-trans conformer is energetically favorable. The exception is 5-vinyloxyacridine for which thes-cis conformation is more favorable. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 12, pp. 2439–2442, December, 1998.     

15N and17O NMR spectra of vinyl ethers of pyridine and quinoline

Conclusions ¹⁵N (¹⁴N) and¹⁷O NMR spectra have been obtained on vinyl ethers of pyridine and quinoline, with unenriched samples. The principal factor determining the chemical shifts is p- conjugation of the unshared pairs of the heteroatom with the unsaturated fragments of the molecule; an additional contribution in the case of the¹⁵N signals comes from interaction of the nitrogen atom with a proton through space.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 4, pp. 769–773, April, 1987.     

Pyrroles from ketoximes and acetylene

The ¹³C NMR spectra of eight 2-alkyl- and 2,3-dialkyl-1-vinylpyrroles were studied. The ¹³C chemical shifts of all of the carbon atoms of the ring and the vinyl group depend substantially on the position and structure of the alkyl substituent. As the branched character of the alkyl group in the 2 position increases, the signal of the -carbon atom of the vinyl group is shifted to weak field due to weakening of the p- conjugation in the N-vinyl group because of disruption of its coplanarity with the pyrrole ring. The conjugation between the double bond and the pyrrole system involves competition for possession of the p electrons of the nitrogen atom.See [16] for communication II.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 350–354, March, 1978.     

Intramolecular specific C-H... N interactions with participation of the pyridine ring nitrogen atom and amino and imino groups in 2-substituted 1-vinylbenzimidazoles,according to1H and13C NMR data

In 1-viny1–2,2-pyridylbenzimidazole, a double intramolecular specific C-H...N interaction is accomplished between the -H of the vinyl group with the pyridine ring nitrogen and between the H³ atom of the pyridine ring and the benzimidazole ring nitrogen. In 1-viny1–2-aminobenzimidazole, there are no intramolecular interactions between the hydrogen atoms of the vinyl group and the nitrogen of the amino group. In 1,3-divinyl-2-iminobenzimidazole, the specific interaction of the imino group nitrogen with the -cis-hydrogen of the vinyl group is greatly weakened by a degenerate tautomeric equilibrium.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 12, pp. 2786–2791, December, 1991.     

Decomposition of vinyl ethers by alkalide K, K(15-crown-5)2 via organopotassium intermediates

The structure of vinyl ethers determines the direction of the C-O bond cleavage by alkalide K⁻, K⁺(15-crown-5)₂1. Highly reactive organopotassium compounds are intermediate products formed in the system containing phenyl vinyl ether, butyl vinyl ether, ethylene glycol butyl vinyl ether or triethylene glycol methyl vinyl ether. Vinylpotassium and butylpotassium react with 15-crown-5. The oxacyclic ring of the latter is opened in this case. Organopotassium ethers possessing CH₂CH₂O units eliminate ethylene. It results in various potassium alkoxides. The reaction of 1 with butyl vinyl ether occurs very slow as compared to other vinyl ethers and most of other reagents used till now.     

Crystal Structure of 6-Chloro-4-nitro-2-phenylpyrimidine

The crystal structures of 6-chloro-4-nitro-2-phenylpyrimidine and 6-chloro-2-phenylpyrimidine have been determined using X-ray diffraction. The effect of the nitro group and the endocyclic nitrogen atoms on the geometric parameters of the 2- and 4-nitropyrimidine molecules, and also related -nitroazines are compared.     

End-Functionalized polymers by living cationic polymerization. IV. Poly(vinyl ethers) with acidic or basic terminal groups by functional initiator method

Carboxylic acid or primary amine-terminated poly(isobutyl vinyl ethers) were synthesized by living cationic polymerizations with functionalized initiators (CH₃CHIO? CH₂CH₂ ? X; X: that are the adducts of the corresponding vinyl ethers (CH₂ ? CH ? OCH₂CH₂? X) with hydrogen iodide. In the presence of iodine, these initiators induced living cationic polymerization of isobutyl vinyl ether to give polymers with the α-end group of X originating from the initiators. The polymer molecular weights were regulated by the monomer to initiator feed ratio and the molecular weight distributions were very narrow (M _w/M _n ≤ 1.15). Subsequent deprotection of the terminal group X led to polymers with a terminal carboxylic acid or primary amine. ¹H- and ¹³C-NMR analyses showed that the end functionalities of these polymers were all close to unity.     

Hydroxyl Protection. III. Synthesis and Cleavage of 2-(Phenylseleno)Ethyl Ethers

During a quest of new hydroxyl-protecting groups, our attention was focused at one time on the 2-(phenylseleno)ethyl residue. It has been established that selenides are responsive to oxidation by H₂ O ₂,² O ₃,³IO₄,⁴etc., to afford selenoxides; aryl alkyl selenoxides undergo facile thermal decomposition⁵ at room temperature or below. Thus starting from 2-(phenylseleno)ethyl ethers (1), the reaction sequence would lead to vinyl ethers and PhSeOH via the intermediates (2). As vinyl ethers are easily hydrolyzed on contact with mineral acids to acetaldehyde and alcohols, the value of the PhSeCH₂CH₂ group for blocking hydroxyl becomes clear.