E and Z stereoisomers of compounds of the phthalide series

The stereospecific position of the H⁴ proton in the PMR spectra of 3-benzyl-idenephthalides identifies unambiguously the E and Z isomers in a mixture. The IR spectra of off-planar deformation vibrations of the C=C bond in the 990–970 cm^–1 region have strong absorption bands, assigned to the E and Z isomers. The strong short-wave band (260 nm) for 3-benzylidenephthalides, having only one benzene ring in the indan moiety, suggests the presence of the E form (=28,000). The long-wave absorption band at 390–430 nm belongs to the Z isomers (=21,000–31,000). 3-Benzylidenephthalides which have no carbonyl groups in their molecules, show fluorescence (_f1=540–560 nm in EtOH).N. N. Semenov Institute of Chemical Physics, Russian Academy of Sciences, 117977 Moscow. Translated from Izvestiya Akademii Nauk, Seriya Khimicheskaya, No. 2, pp. 309–314, February, 1992.     

Insect pheromones and their analogs. VIII. Synthesis of the (Z) and (E) isomers of 2-methyloctadec-7-ene and of 2-methyl-7,8-epoxyoctadecane

A highly stereospecific method for the synthesis of racemic (Z)-disparlure has been developed which is based on the reduction of 2-methyloctadec-7-yne with the aid of 9-borabicyclo[3.3.1]nonane and the epoxidation of the resulting (Z)-2-methyloctadec-7-ene with p-methoxycarbonylperbenzoic acid. The¹³C NMR spectra of the (Z) and (E) isomers of 2-methyloctadec-7-ene and 2-methyl-7,8-epoxyoctadecane, which unambiguously confirm the structures of these compounds, are given. It has been established that (E)-2-methyloctadec-7-ene exhibits a moderate attractant activity while the (Z) isomer does not attract the gypsy moth. The addition of 5–25% of (E)-disparlure increases the biological activity of (Z)-disparlure.Institute of Chemistry, Bashkir Branch, Academy of Sciences of the USSR, Ufa. Translated from Khimiya Prirodnykh Soedinenii, No. 5, pp. 630–634, September–October, 1983.     

Use of13C-13C spin-spin coupling constants for establishing the configuration of 1-alkoxy-1-aminoxyethanes

Conclusions Direct¹³C-¹³C coupling constants were used to establish the configuration of 1-alkoxy-1-aminoxyethanes. The compounds are mixtures of Z and E isomers, of which the E isomers are more stable.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 9, pp. 2137–2138, September, 1985.     

Rearrangement of 1-oxa-2-azoles. 6. Rearrangement of oximes of 3-(piperidinocarbonyl) isoxazoles

The Z isomers of oximes of 3-(piperidinocarbonyl)isoxazole are isomerized by acid to the thermodynamically more stable E isomers, which in the presence of base readily recyclize to the corresponding 3-amino-1,2,5-oxadiazoles.For Communication 5, see [1].Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 7, pp. 979–981, July, 1991.     

NMR spectra and configurations of monosubstituted glyoximes

By comparing the results of multinuclear NMR spectroscopy we have determined unequivocally the structures of the E,E and Z,E isomers of monosubstituted methyl-, phenyl-, and chloroglyoximes. Criteria are given for determining the structure of other glyoximes.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 5, pp. 1023–1027, May, 1990.     

Theoretical Study of Molecular Structure, Tautomerism, and Geometrical Isomerism of N-Methyl- and N-Phenyl-Substituted Cyclic Imidazolines, Oxazolines, and Thiazolines

The geometries of various tautomers and isomers of 2-methylamino-2-imidazoline, 2-methylamino-2-oxazoline, 2-methylamino-2-thiazoline, 2-phenylamino-2-imidazoline, 2-phenylamino-2-oxazoline, and 2-phenylamino-2-thiazoline have been studied using the Becke3LYP/6–31+G(d,p) DFT, ONIOM(Becke3LYP/6–31+G(d,p):HF/3–21G^*) and ONIOM(Becke3LYP/6–31+G(d,p):AM1) methods. The optimized geometries indicate that these molecules show a distinctly nonplanar configuration of the cyclic moieties. In the gas phase, the amino tautomers (with exception of 2-phenylamino-2-imidazoline) are computed to be more stable than the imino tautomers. Of the two possible (E and Z) isomers of methyl and phenyl derivatives of imino-oxazolidine and imino-thiazolidine species, the (Z) isomers have the lowest energy. The iminozation free energies in the gas phase were found to be 5 – 15 kJ/mol. Absolute values of K _T depend strongly on the accuracy of the method used for calculation of free energy. Solvation (using the MD simulations) causes, in most cases, a shift in tautomeric preference toward the imino species.     

NMR spectral study of the structure of 2-amino-4-thiazolinones

As a consequence of partial double bond nature of the exocyclic C-N bond, 2-methylamino-4-thiazolinone exists in DMSO-D₆ as a mixture of E and Z conformers of the amino form with predominance of the sterically favored E conformer. 2-Phenylimino-4-thiazolidinone in the same solvent exists as a mixture of the E and Z isomers of the imino form.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 544–548, April, 1986.     

Study of three-dimensional structures of benzoylpyridine oximes and their ethers by 1H and 13C NMR spectroscopy

The ¹H and ¹³C NMR spectra of the E and Z isomers of 2-, 3-, and 4-benzoylpyridine oximes and their ethers were analyzed thoroughly, and the ¹H-¹³C spin-spin coupling constants (SSCC) were determined. It was established that the magnitude of the effect for the quaternary carbon atoms in the E and Z isomers depends on the site of substitution in the pyridine ring. It was assumed that the intermolecular hydrogen bond is stronger in the E form than in the Z form. The existence of the Z isomer of 2-benzoylpyridine oxime in deuterochloroform with an intramolecular hydrogen bond was proved.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 203–208, February, 1990.     

Structure of 2-benzothiazolylhydrazones of aromatic and aliphatic aldehydes

On the basis of data of ¹³C and ¹H NMR and IR spectroscopy, it was shown that 2-benzothiazolylhydrazones of aliphatic aldehydes were in solution as a mixture of E and Z isomers, and hydrazones of aromatic aldehydes were in solution only as E isomers. All investigated compounds existed in solution mainly in an amino tautomeric form, and the content of the imino form did not depend on the nature of the aldehyde fragment.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 550–558, April, 1993.     

9-Imino(amino)-10-sila-2-azaanthracenes

9-Imino derivatives of dihydrosilaazaanthracenes were obtained from 10,10-diorganosila-2-azaanthrones. It was shown by PMR spectroscopy that they exist in the form of Z and E isomers. The azomethines were reduced to secondary amines, from which the N-acyl derivatives were obtained.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 1, pp. 126–129, January, 1989.     

Synthesis of 2-keto-4-phosphorylbutyric acids and their derivatives

The Claisen condensation of 3-phosphorylated propionitriles with diethyl oxalate has been examined. The product of the condensation of 3-(methylethoxyphosphinyl)propionitrile, following hydrolysis, has been shown to be the enol form (Z-isomer) of 4-(methylhydroxyphosphinyl)-3-cyano-2-ketoburyric acid. On crystallization from water, the other isomers (the E-isomer of the enol or the keto-forms) were not isolated. Distillation of the products of silylation of the reaction mixture with hexamethyldisilazane gave both geometric isomers of the enol (Z and E). In aqueous solution, the enol gradually cyclizes to give 2-hydroxy-3-(methylhydroxyphosphinyl)citraconimide.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 9, pp. 2120–2127, September, 1990.     

Hydrazones

The products of the reaction of 1-chloro- and 1,4-chlorophthalazines with hydrazine are the E isomers of the hydrazones of the corresponding phthalazone rather than hydrazinophthalazines, as previously assumed. The hydrazones of 2-methylphtalazones exist in the Z form.See [1] for communication XXXIX.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 402–409, March, 1976.     

Structure and dual reactivity of 2-phenylpemoline

5-Phenyl-2-phenylimino-4-oxazolidinone exists in DMSO-D₆ in the form of a mixture of the E and Z isomers of the imino tautomer, but it crystallizes in the amino form. Parallelism between the basicity and nucleophilicity of the reaction centers of this mesomeric anion is observed when the alternative isomers (and the tautomers corresponding to them) differ significantly in stability. If this condition is not fulfilled, these parameters do not coincide, as is illustrated in the example of its methylation reaction.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 388–392, March, 1989.     

Synthesis of heterocycles from products of the anion arylation of unsaturated compounds. 3. 2-arylimino-5-arylmethyl-4-thiazolidones

The reaction of esters of 3-aryl-2-bromopropionic acids with N-arylthioureas gives 2-arylimino-5-arylmethyl-4-thiazolidones, which exist in solution as (E) and (Z) isomers of the imino form.For Communication 2, see [1].I. Franko Lvov State University, Lvov 290602, Ukraine. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 555–559, April, 1998.     

NMR investigation of some α,ω-disubstituted farnesanes

Conclusions New, independent evidence for the twisted conformation of linear isoprenoid molecules has been obtained from a study of the¹³C NMR spectra of the ethyl ester isomers of 11-bromo-10-hydroxy, 10, 11-epoxy, and 10, 11-dihydroxy-3, 7, 11-trimethyldodeca-2E/Z, 6E/Z-dienecarboxylic acids when compared with the corresponding ethyl esters of 3, 7, 11-trimethyldodeca-2E/Z,6E/ Z,10-trienecarboxylic acid (farnesyl ester). Further information came from an NOE study of the latter and the ethyl esters of 10-formyl-3,7-dimethyldeca-2E,6E/Z-dienecarboxylic acid.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 10, pp. 2194–2198, October, 1987.     

Stereoisomerism ofβ-polyfluoroalkyl-α,β-enones

-Polyfluoroalkyl-,-enones formed in the E,Z form are converted by the action of atmospheric oxygen into a 937 mixture of E,Z and Z,E isomers in the dark and 6040 mixture of these isomers in the light. The Z isomer of 1-phenyl-4,4, 4-trifluoro-2-buten-1-one was isolated preparatively for the first time and its E conformation relative to the C-C bond was established. The Z,E isomer spontaneously transforms into the indicated equilibrium mixtures.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 7, pp. 1685–1689, July, 1991.     

Structure of 1-aryl-3-alkyl-5-(2-benzothiazolyl)formazans

The isomeric and tautomeric structures of 1-aryl-3-alkyl-5-(2-benzothiazolyl)formazans in solutions were investigated by means of NMR, IR, and electronic spectroscopy. It is shown that the nature of the solvent and the alkyl substituent in the 3 position affects the ratio of the Z and E isomers relative to the C=N bond of the azohydrazone chain. An increase in the length of the alkyl substituent in the 3 position leads to preponderance of the Z isomer in solution, while branching stabilizes the Z configuration with an N²...HN⁵ intramolecular hydrogen bond (IMHB), regardless of the solvent. The nature of the solvent has a significant effect on the ratio of the amino and imino tautomeric forms of the E isomers. The benzothiazolylhydrazone form predominates in CHCl₃, while the tautomer with a benzothiazolidene fragment is the major form in DMSO.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 6, pp. 834–839, June, 1993.     

New synthesis of monomethyl ethers of triols — Extraction agents for boric acid

Conclusions A new method for the synthesis of monomethyl ethers of triols starting from acetylenic ketones has been developed.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 3, pp. 621–623, March, 1987.     

Stereochemistry of 16-Membered Azo- and Azoxycrown Ethers. Structures of Their Sandwich Potassium Iodide Complexes

16-Membered dibenzoazo- and dibenzoazoxycrown ethers have been synthesized. The Z and E isomers of the azocrown compound have been separated and the geometry of the –N=N– and –-N(O)=N–- groups determined. Potassium iodide complexes of the azo- and azoxycrown ethers were obtained and their structures were determined by the X-ray method. The crystal of the azocrown ether complex is triclinic, space group P¯1, a = 21.071(5), b = 12.112(4), c = 8.757(2) Å = 81.28(2), = 84.66(2), = 107.49(2)°. The azoxycrown ether complex is monoclinic, space group C2/c, a = 15.648(3), b = 19.597(4), c = 14.651(3) Å; = 111.30(3).