1-azabicyclic compounds. 22. Stereochemistry and13C NMR spectra of salts of pyrrolizidine and its homologs with protonic acids

¹³C NMR spectra were obtained for pyrrolizidinium salts and their homologs and their signals were assigned. With the exception of highly strained cis-3,8-H-cis-5,8-H-3,5-dimethylpyrrolizidine (VI), all the bases studied upon their direct mixing with CF₃CO₂H form salts only with cis-fused rings in the cation. Mixtures of salts with cis- and trans-fused pyrrolizidinium fragments are formed upon the reaction of cis-3,8-H-methy1- (III) and cis-3,8-H-cis-5,8-H-3,5-dimethylpyrrolizidine (VI) under conditions close to those for kinetically-controlled amine protonation. The¹³C NHR spectra of the isomeric pyrrolizidinium salts obtained as a result of the absorption of base VI by sulfuric acid were used to evaluate the conformational equilibrium in the starting compound VI. The¹³C NMR chemical shifts of unsubstituted trans-fused pyrrolizidinium salts were predicted.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 12, pp. 1638–1647, December, 1985     

Research on 1-AZA two-ring systems. 21. Basicities,stereochemistry, and 1H and 13C NMR spectra of pyrrolizidine and its homologs in aqueous and aqueous acetonitrile solutions. Prediction of the pKa value of trans-fused pyrrolizidine

The basicities of pyrrolizidine and its homologs in aqueous and aqueous acetonitrile solutions at 25 ° C were determined. It is shown that among 3-alkylpyrrolizidines, the isomers with cis configurations have higher pK_a values than the isomers with trans configurations. On the basis of a comparative study of the ¹H and ¹³C NMR spectra it was concluded that cis-3,8-H-cis-5,8-H-3,5-dimethylpyrrolizidine in aqueous solutions exists chiefly in the trans-fused form, whereas conformationally heterogeneous pyrrolizidines with primarily cis-fused rings experience a shift of the equilibrium to favor an increase in the cis-fused conformations when a nonpolar solvent is replaced by a polar solvent. The basicity of the trans-fused conformation of pyrrolizidine is predicted on the basis of the data obtained.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 1, pp. 39–46, January, 1982.     

Research on two-ring 1-aza compounds

5-Hydroxymethyl-1,2-dihydropyrrolizines were catalytically hydrogenated to 3(5)-hydroxymethylpyrrolizidines, and the ratios of the isomers in the products of the reaction, which proceeds stereoselectively, were determined. The configuration of the diastereomers was established on the basis of the results of catalytic isomerization, a study of the chromatographic behavior of the isomers on a polar stationary phase, and a discussion of the isomeric composition of the hydrogenation products in the light of the general principles of the stereochemistry of catalytic hydrogenation. trans- and cis-3,8-H-3-Hydroxymethylpyrrolizidine and trans-3,8-H-3-methyl-trans-5,8-H-5-hydroxymethylpyrrolizidine were isolated from the mixtures of isomers. The existence of an intramolecular hydrogen bond in trans-3,8-H-3-hydroxymethyl- and trans-3,8-H-3-methyl-trans-5,8-H-5-hydroxymethylpyrrolizidine was shown by IR spectroscopy.See [1] for communication XIITranslated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 484–489, April, 1976.     

Research on 1-azabicyclic systems

Epimeric 3-methylpyrrolizidines were separated preparatively. Competitive quaternization of the mixture of isomers with n-propyl iodide and catalytic isomerization were used to obtain trans-3, 8-H-3-methylpyrrolizidine. cis-3,8-H-3-Methylpyrrolizidine was isolated from the mixture by quaternization with benzyl chloride and subsequent hydrogenolysis of the resulting quaternary salt. The pK_a values of trans- and cis-3,8-H-3-methylpyrrolizidines, pyrrolizidine, and indolizidine were measured. It is shown that in a series of saturated amines with a tertiary nitrogen atom pyrrolizidine and 3-methylpyrrolizidines are among the strongest bases.See [1] for communication XII.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 8, pp. 1060–1064, August, 1976.     

Research on 1-azabicyclic compounds

1-(2-Furyl)-3-amino-4,4-dimethylpentane was used to obtain 3-tert-butyl-1,2-dihydropyrrolizine, the catalytic hydrogenation of which over Rh/Al₂O₃ at room temperature gives a mixture of cis- and trans-3,8-H-3-ter-butylpyrrolizidines with predominance of the cis isomer, whereas hydrogenation at 90–100 °C gives a mixture containing the trans isomer as the principal component. The three-dimensional structures of the isomers follow from data on the catalytic hydrogenation and isomerization and the IR, Raman, and PME spectra. A considerable percentage of the trans-fused form is characteristic for cis-3,8-H-3-tert-butylpyrrolizidine.     

Investigation of 1-azabicycles

The composition of mixtures of epimeric 3-methylpyrrolizidines obtained by four methods was determined by gas-liquid chromatography (GLC). The data presented make it possible to select a method for the preparation of a mixture of isomers of 3-methylpyrrolizidine with predominance of trans- or cis-3,8-H-3-methylpyrrolizidine.See [1] for communication IX.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 329–331, March, 1973.     

Semi-empirical topological method for the prediction of the chromatographic retention of cis- and trans-alkene isomers and alkanes.

A new index is proposed for the prediction of the chromatographic retention of the cis- and trans-n-alkene isomers and alkanes. This index is based on the hypothesis that the chromatographic retention of the molecule is due to the interaction of each carbon atom with the stationary phase, and consequently the index is reduced by its neighbours' steric effects. The topological values are obtained by a numerical approximation considering the general behaviour of the chromatographic retention of the compounds. The simple linear regressions between the chromatographic retention and the index proposed for all branched alkanes and also isomers of the studied straight-chain C5 and C14 alkenes (1-ene, cis- and trans-2-, 3-, 4-, 5-, 6- and 7-enes) is very good (the correlation coefficient is r = 0.9999), and the elution sequence is correct for most of them. The models have a high predictive ability, as established by cross-validation values (r2cv). Thus, this new method, different from those already existent, can be used as complementary tool for the elucidation of the molecular structure, or prediction of the chromatographic retention of the cis- and trans-alkene isomers and branched alkanes. It could be extended with success, in the future, to the other types of compounds.     

一种新的改性聚乙二醇毛细管气相色谱固定相

合成了一种新的聚乙二醇衍生物，将其用作毛细管气相色谱固定相，研究了其色谱性能，并成功地分离了二甲苯、氯甲苯、溴甲苯、二氯苯等二取代苯位置异构体；并对其手性分离能力进行了初步研究和讨论。     

Gas-chromatographic studies of the sorption thermodynamics of adamantanes on a carbon adsorbent modified with polyethylene glycol with β-cyclodextrin additives

The thermodynamic characteristics of sorption of adamantane and its derivatives on a mixed stationary phase consisting of a graphite-like solid substrate, polyethylene glycol, and β-cyclodextrin (βCD) were determined by gas chromatography. The introduction of β-CD additives to a polar polymer matrix was shown to considerably decrease the chromatographic retention of the sorbates, which is evidence of the macrocyclic effect. The presence of β-CD molecules was found to increase the selective properties of the mixed sorbent with respect to the structural isomers of adamantanes.     

Capillary gas chromatography of C6−C14 n-alkenes on polyphenyl ether and polyethylene glycol 4000

Summary The retention indices (I) and their structural increments (l/°C, H, l) of C₆–C₁₄ n-alkenes on polyphenyl ether (PFE) and C₁₂–C₁₄ n-alkenes on polyethylene glycol 4000 (PEG) at 20–160 °C have been determined and correlated with the molecular structure of the isomers. A number of common regularities in gas chromatographic behaviour on these liquid phases and squalane (SQ) [1–3] have been found. On PFE the elution order of isomeric n-alkenes is similar to that on SQ (except C₈–C₁₀ 1-alkenes and cis-4-tetradecene), for pairs with cis- and trans-configuration it depends on the column temperature, position of double bond and the number of carbon atoms (n) in the molecule. On PEG the cis- are always retained longer than the corresponding trans-alkenes. The linear relationships between 1 and n on PFE and PEG are given in equation form.     

Colloid stationary phases containing aerosil

Summary Binary colloid systems, including aerosil and an organic modifier (e.g. polyethylene glycol 400 or squalane) are suggested as stationary phases for gas chromatography. The dependence of solute retention on the composition of the phases is studied and the influence of the sol — gel transition on the retention indicated.     

Capillary gas chromatography-mass spectrometry of all 93 acyclic octenes and their identification in fluid catalytic cracked gasoline

The Kováts retention indices of all 93 acyclic octenes on polydimethylsiloxane and squalane as stationary phases as well as their mass spectra were measured. The means of gas chromatography-mass spectrometry (GC-MS) were used for confirmation of GC identification as well as for mass spectrometric deconvolution of the majority of gas chromatographic unseparated isomeric octene peaks. The distinction between corresponding E and Z acyclic octenes, that is either difficult or even impossible by means of GC-MS, was obtained on the basis of larger temperature coefficients of retention indices for Z isomeric octenes than for corresponding E isomers. The retention data expressed as homomorphy factors were correlated with the degree of branching, position of double bond, and position of alkyl group with respect to the double bond of acyclic octenes, and the structure-retention relationships were formulated. The 81 acyclic octenes were identified in FCC gasoline.     

Gas-chromatographic analysis of alkylated derivatives of carane and of cycloheptane in capillary columns

The retention indices of synthesized alkyl derivatives of carane and of cycloheptane in capillary columns with tricresyl phosphate and squalane at 70°C have been determined. The influence of the structure of the hydrocarbons studied on the values of their retention parameters is considered. An estimate is given of the nature of the interrelationship between the physical properties of these hydrocarbons and their retention indices on a nonpolar stationary phase.     

Separation behaviour of nitroxylene isomers on polyols and polyethers in gas-liquid chromatography

Of the six nitroxylene isomers, 2,4- and 2,3-nitroxylene are the most difficult to separate by GLC, but they have been effectively separated on various acidic polyols as stationary phases. Although polyethylene glycol could not generally separate the 2,4- and 2,3-nitroxylene isomers, polyethylene glycol 20M could, and polypropylene glycol could separate all the six isomers effectively.     

全丁基-β-环糊精与硝酸银的混合液作为毛细管气相色谱固定相的研究

 将合成的全丁基-β-环糊精+硝酸银(聚乙二醇400作溶剂)混合固定液静态涂渍在弹性石英毛细管柱内壁,7组对映异构体、4组芳香族位置异构体化合物等在该柱上得到满意分离。通过测定以上化合物在该柱及全丁基-β-环糊精柱上的热力学参数(焓、熵、自由能及焓变差、熵变差),探讨了固定液对所测化合物的色谱分离机理。结果表明,混合固定液对所测化合物具有协同效应     

Influence of the structure of the alcoholic modifier on the enantioselective separation of nadolol

The influence of the structure of the alcoholic modifier of the mobile phase on the liquid chromatographic separation of the optical isomers of nadolol on a Pirkle-type chiral stationary phase was investigated. The isomers were separated as their chiral 1-naphthylureides on a column consisting of 3,5-dinitrobenzoyl- -leucine covalently bound to 3-μm aminopropylsilica, using an eluent consisting of n-hexane modified with an alcohol. A number of straight-chain, branched and unsaturated alcohols with carbon numbers ranging from 1 to 8 were evaluated. The choice of alcohol influenced both retention and selectivity, with optimum stereoselectivity being observed for C₃. The alcoholic modifiers selectively affected the retention and resolution of the two pairs of enantiomers that constitute nadolol. Thus chromatograms displaying two, three or four peaks could be obtained, depending on which modifier was employed. The best separation of all four isomers was achieved with ethanol as the modifier.     

Gas-chromatographic analysis of alkylated derivatives of carane and of cycloheptane in capillary columns

The retention indices of synthesized alkyl derivatives of carane and of cycloheptane in capillary columns with tricresyl phosphate and squalane at 70°C have been determined. The influence of the structure of the hydrocarbons studied on the values of their retention parameters is considered. An estimate is given of the nature of the interrelationship between the physical properties of these hydrocarbons and their retention indices on a nonpolar stationary phase.Institute of Physical Organic Chemistry, Academy of Sciences of the Belorussian SSR, Minsk. Translated from Khimiya Prirodnykh Soedinenii, No. 4, pp. 427–432, July–August, 1986.     

有机聚合物固定相的色谱性能

研究了五种有机聚合物固定相的色谱性能.选择在170℃柱温下测定其极性常数,并以下式计算各种填料的极性常数:X′=Ix-653,Y′=Iy-590,Z′=Iz-627,U′=Iu-652,S′=Is-699.式中Ix、Iy、Iz、Iu、Is分别为柱温170℃测得的5种表征物质的保留指数,同时以实验验证了该方法的有效性和实用性.还测定了这些固定相在高纯氮气和空气中的热分析(TG、DTA)曲线,研究了DTA曲线产生峰值的原因,指出了其上限使用温度.扩展了此类固定相的应用范围.此外,还对保留值与柱温的关系进行了研究.     

Semi-empirical topological index: development of QSPR/QSRR and optimization for alkylbenzenes

The semi-empirical topological index, I(ET), was developed and optimized to describe the chromatographic retention of alkylbenzenes on the squalane stationary phase. The simple linear regression between the chromatographic retention and the proposed index, for 122 alkylbenzenes studied, is of good quality (determination coefficient, r(2)=0.9996, standard deviation, S.D.=5.5, and leave-one-out cross-validation correlation coefficient, r(CV)(2)=0.9996). The predictive ability of I(ET) was also verified for stationary phases with two different polarities (SE-30 and Carbowax 20 M), and good results were obtained, especially for the stationary phase with low polarity, showing that the specific molecular interactions occur on highly polar phases. The I(ET) was applied to construct quantitative structure-property relationship (QSPR) models for representative properties such as boiling point, Bp(degrees C), octanol/water partition coefficient, log P, van der Waals volume (V(W)) and molar refractivity (R(M)). Satisfactory quality QSPR models were obtained with Bp, V(W) and R(M) showing that the molecular size and dispersive forces are dominating factors with respect to the chromatographic retention.