Synthesis and Stereochemistry of Substituted 1,3-Dioxa-2-silacyclohexanes: VII. Synthesis and Stereochemistry of Substituted 2-Vinyl-2-methyl-1,3-dioxa-2-silacyclohexanes

The stereochemistry of substituted 2-vinyl-2-methyl-1,3-dioxa-2-silacyclohexanes was studied by ^1Hand ^13C NMR spectroscopy. The configurational and conformational assignment of a mixture of 2-vinyl-2,4-dimethyl-1,3-dioxa-2-silacyclohexane diastereomers with various ratios of the cis and trans forms was made. The molecules of both conformers occur chiefly in the chair conformartion with equatorial location of the methyl group at the C⁴ atom. The experimental data were confirmed by AM1 and MM+ optimization of the molecular geometry.     

8,10-Dimethyl-7,13-dioxa-10-azaspiro[5.7]tridecane — the first representative of perhydro-1,3-dioxa-6-azocines

The first representative of perhydro-1,3-dioxa-6-azocines, 8,10-dimethyl-7,13-dioxa-10-azaspiro[5.7]tridecane, was synthesized by the reaction of 4-methyl-1-oxa-4-azaspiro[4.5]decane with propylene oxide. The structure of the compound has been confirmed by IR and¹H and¹³C NMR spectroscopy and mass spectrometry.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1838–1839, September, 1995.     

Synthesis and structure of methyl-substituted 1,3-Dioxa-2-Silacylohexanes

The reaction of dimethyl(diethylthio)silane with 1,3-diols gave methyl-substituted 1,3-dioxa-2-silacyclohexanes.¹H and¹³C NMR spectroscopy were used to study the configuration and predominant conformations of the compounds studied.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 6, pp. 845–851, June, 1986.     

Synthesis of difunctional organooxasilacycloalkanes

2,8-Dichloro-2,4,4,6,6,8,10,10,12,12-decamethyl-5-carbacyclohexasiloxane, 4,7-dichloro-2,2,4,7-tetramethyl-1,3-dioxa-2,4,7-trisilacyclohepatane, and 4,8-dichloro-2, 2,4,8-tetramethyl-1,3-dioxa-2,4,8-trisilacyclooctane were prepared for the first time by heterofunctional condensation of 1,1,7,7-tetrachloro-1,3,3,5,5,7-hexamethyl-4-carbatetrasiloxane with 1,3-dihydroxy-1,1,3,3-tetramethyldisiloxane, of 2,2,5,5-tetrachloro-2,5-disilahexane with dihydroxydimethylsilane, and of 2,2,6,6-tetrachloro-2,6-disilaheptane with dihydroxydimethylsilane, respectively. Hydrolysis of the resulting compounds afforded the corresponding dihydroxy derivatives, andtrans-isomers of some of these derivatives were isolated in individual form. Published inIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1436–1441, August, 2000.     

Crystal and molecular structure of 2,2,6-trimethyl-6-selenono-1,3-dioxa-2-sila-6-phosphacyclooctane

An X-ray structural study of 2,2,6-trimethyl-6-selenono-1,3-dioxa-2-sila-6-phosphacyclooctane (R = 0.029 for 1340 reflections) was carried out. The molecule has C_s symmetry and its eight-membered heterocycle has a crown conformation. The intramolecular Si … Se distance of 4.437(1) Å precludes the possibility of the corresponding transannular attractive interaction.     

Germa-2-dioxa-1,3-cycloalcanes

The action of the α-, β- and γ-diols on the dialkyl(aryl)-bis(dialkylamino) germanes R₂Ge(NR'₂)₂ leads, in high yields, to the dialkyl(aryl)-2,2-germa-2-dioxa-1,3-cycloalkanes. The IR. and NMR. spectral study in the presence of Eu(Dpm)₃ allowed to demonstrate a dimerisation by coordination in some of these heterocycles. In this complex, the germanium is hexacoordinated by association with the two oxygens of the second associate molecule. Its hybridation state is sp₃d₂ or spd₄ (D_3h symmetry, prismatic structure). These low energy association are ruptured in solution at moderate temperatures; these heterocycles are monomers by ebulliometry in benzene. This association is disfavoured by the presence of substituents on the cycle and by hindering substituents with donor effect on the germanium. The diminution of nucleophilicity of the oxygens by mesomeric effect with neighbouring π systems also prevents any association.     

Conformational analysis of 2,2-dimethyl-5-alkyl-1,3-dioxa-2-silacyclohexanes

Study of conformational isomerization of 2,2-dimethyl-5-alkyl-1,3-dioxa-2-silacyclohexanes using quantum-chemical HF/6-31G(d) and PBE/3z approximations showed that its route involves an equilibrium between the chair conformers with different orientation of substituent at C⁵ ring atom and proceeds through a transition state corresponding to the 2,5-twist conformation. Molecular dynamics method showed that at room temperature this conformation transforms into the equatorial or axial chair conformers through 1,4-twist or sofa forms. Based on the experimental and theoretical values of vicinal ¹H NMR coupling constants we determined quantitative conformational composition of the molecules of these compounds and the values of ??G ⁰ of the conformational equilibrium.     

Hydrosilylation reactions of hydrosilatrane and 2-methyl-6-ethyl-1,3-dioxa-6-aza-2-silacyclooctane

Conclusions 1-Hydrosilatrane does not react with monosubstituted ethylenes (or acetylenes) either in the presence of platinum or rhodium complexes or upon initiation of the reactions using organic peroxides, UV irradiation, or thermal methods. By contrast, 2-methyl-6-ethyl-1,3-dioxa-6-aza-2-silacyclooctane readily takes part in hydrosilylation of the indicated unsaturated compounds when Rhacac (CO)₂ is present.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khirnicheskaya, No. 4, pp. 899–901, April, 1986.     

Mass spectra and stereochemistry of alkylsubstituted 2,2-diphenyl-1,3-dioxa-2-germacyclohexanes

The correlations between electron impact induced formation of fragment [M ? C₆H₆]⁺˙ from alkyl-substituted 2,2-diphenyl-1,3-dioxa-2-germacyclohexane (1) and the peculiarities of the molecular structures were found. Benzene elimination is regiospecific and stereoselective, resulting from the abstraction of an axial phenyl group and a hydrogen atom from the C-4 or C-6 position of the ring.     

Synthese und NMR-spektroskopische Untersuchungen von Dibenzo[d,g]-1,3-dioxa-2-element-6-silocinen

Synthesis and NMR Spectroscopic Investigations of Dibenzo [d,g]-1,3-dioxa-2-element-6-silocine Bis-(o-halogenoaroxy)silanes react with sodium via metallation and a fast two-step [1.3]-rearrangement to the sodium salts of bis(o-hydroxyaryl)silanes. These are cyclized in a one-pot-reaction with element halides of silicon, phosphorus and arsenic to the title compounds of the general formula R¹R²Si(C₆H₄O)₂E (E = SiR₂, P(Y)R, As(Y)R). One conformer is prefered according to N.M.R. spectroscopical investigations.     

Free-radical addition of phenyl- and diphenylphosphines to 2-vinyl-1,3-dioxa-6-aza-2-silacyclooctanes

Conclusions Phenyl- and diphenylphosphines add to 2,6-dimethyl-2-vinyl-1,3-dioxa-6-aza-2-silacyclooctane upon the action of UV irradiation to form 2,6-dimethyl-2-[(2-phenylphosphino)ethyl)]-1,3-dioxa-6-aza-2-silacyclooctane and 2,6-dimethyl-2-[(2-diphenylphosphino)ethyl]-1,3-dioxa-6-aza-2-silacyclooctane, respectively.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 11, pp. 2615–2616, November, 1985.     

Synthesis and structure of 6-substituted 9-(2-ethoxy-1,3-dioxan-5-yl)purines

The reaction of 4-chloro-5-amino-6-(1,3-dihydroxy-2-propyl)aminopyrimidine with excess ethyl orthoformate gave a cyclic acetal, viz., 6-chloro-9-(2-ethoxy-1,3-dioxan-5-yl)purine, amination of which yielded 6-amino-9-(2-ethoxy-1,3-dioxan-5-yl)purine. The presence of two configurational isomers with a diaxial orientation of the purine ring and the ethoxy group in the trans isomer and an equatorial orientation of the ethoxy group in the cis isomer was established for these compounds by ¹H and ¹³C NMR and IR spectroscopy. The three-dimensional structure of trans-6-chloro-9-(2-ethoxy-1,3-dioxan-5-yl)purine was determined by an x-ray difraction study, and the trans-diaxial orientation of the purine ring and the ethoxy group was confirmed; it is shown that the dioxane ring is in an anti conformation relative to the purine ring.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 7, pp. 976–983, July, 1979.     

Synthesis of siloxanes : XXII. Synthesis and crystal structure of 2-t-butoxy-2,4,6-trimethyl-4,6-diphenyl-(2α,4α 6α)-cyclotrisiloxane

The structure of 2-t-butoxy-2,4,6-trimethyl-4,6-diphenyl-(2α,4α,6α)-cyclotrisiloxane has been determined by an X-ray crystallographic study. The structure revealed confirms the validity of the basis of our ²⁹Si and ¹H NMR assignments previously made to configurational isomers of several model compounds, which are suitable for studying the stereochemistry of substitutions at silicon atoms in siloxanes     

Preparation and some properties of 2H-imidazole 1,3-dioxides,derivatives of alicyclic 1,2-dioximes

The corresponding 2H-imidazole 1,3-dioxides were obtained by the reaction of cyclohexanedione and cycloheptadione 1,2-dioximes with acetone, cyclopentanone, and methyl ethyl ketone. The reactions of these compounds with hydroxylamine hydrochloride, NaBH₄, a Grignard reagent, and acetic anhydride in the presence of H₂SO₄ were studied in the case of 2,2-dimethyl-4,5,6,7-tetrahydro-2H-benzimidazole 1,3-dioxide. Bromination of the latter and 2,2-dimethylcyclohepta-2H-imidazole 1,3-dioxide with N-bromosuccinimide gave the corresponding dibromo derivatives, the bromine atoms in which are replaced by acetoxy and hydroxy groups. 4,7-Dihydroxy-2, 2-dimethyl-4,5,6,7-tetrahydro-2H-benzimidazole 1,3-dioxide, which was obtained by oxidation with MnO₂ was converted to a quinone, viz., 2,2-dimethyl-4,7-dioxo-4,7-dihydro-2H-benzimidazole 1,3-dioxide. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 6, pp. 808–813, June, 1980.     

Synthesis, structures and spectroelectrochemistry of methyl-substituted bis(η-indenyl)iron(II) complexes

Several new methyl-substituted indenyl ferrocenes were prepared by metathesis reactions of the indenide (generated from the appropriate indene with BuLi) with ferrous chloride. The indenides used to prepare new ferrocenes were: 2-methyl-, 1,2-dimethyl-, 4,7-dimethyl-, 1,4,7-trimethyl-, and 1,3,4,7-tetramethyl-indenide. These indenyl ferrocenes, along with those prepared from indenide, 1-methylindenide, and 1,3-dimethylindenide, were then characterized by ¹H and ¹³C NMR, UV/visible spectroscopy, cyclic voltammetry and mass spectrometry. The cyclic voltammetry showed an additive relationship between oxidation potential and the number of methyl groups which is also position-dependent, whereas the UV/visible spectra showed two absorptions essentially unaffected by methyl substitution. Additionally, bis(2-methylindenyl)iron(II) and bis(4,7-dimethylindenyl)iron(II) were characterized by X-ray crystallography.     

N-(2-Thenyl)derivatives of aminoalkyltriethoxysilanes,-silatranes and 2,2-dimethyl-1,3-dioxa-6-aza-silacyclooctane

The reactions of aminoalkylethoxysilanes and 2,2-dimethyl-1,3-dioxa-6-aza-2-silacyclooctane with 2-(chlormethyl)thiophene and its 5-chloroderivative lead to the correspondingN-(2-thenyl) derivatives. TheN-methyl-N-(2-thenyl)aminomethyltriethoxysilane and 5-chlorothyenyl derivative formed are converted by triethanolamine into silatranes.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 384–386, February, 1995.     

1,3-Dioxa-6-chalcogena-2-silacyclooctanes

Conclusions Transetherification of methylvinyldialkoxyslianes by diols (HOCH₂CH₂)₂M (M=O, S, Se, and Te) gave 2-methyl-2-vinyl-1,3-dioxa-6-chalcogena-2-silacyclooctanes CH₃ (CH₂=CH)Si(OCH₂· CH₂)₂M. The IR, NMR, and mass spectra of these compounds were studied.²⁹Si NMR spectroscopy indicated that there is a transannular interaction in such heterocycles only in the case of M=Te.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 8, pp. 1859–1861, August, 1987.     

Structure of 1,4-dichloro-1,4-bis(perfluoroalkyl)-1,3-diazatetra-1, 3-dienes from their13C,19F,and15N NMR spectra

Previously unknown 1,4-dichloro-1,4-bis(perfluoroalkyl)-1,3-diazatetra-1,3-Dienes have been prepared and shown to be mixtures of isomers of Z and E configurations. The structures have been identified and a quantitative estimate made of the ratio of Z and E isomers using¹³C,¹⁹F, and¹⁵N NMR spectroscopy.     

Comparative conformational analysis of 2,2-dimethyl and 2,2,5-trimethyl-1,3-dioxanes and their 2-heteroanalogs with silicon and germanium atoms

Comparative conformational analysis of 2,2-dimethyl- and 2,2,5-trimethyl-1,3-dioxanes as well as their 2-heteroanalogs with silicon and germanium atoms has been performed by means of computer simulation using HF/pVDZ, hybrid DFT PBE/3ξ, and RI-MP2/λ2 methods. The potential energy surface for all the studied compounds has revealed the presence of the chair and 2,5-twist conformers. The latter form, in the case of substituted 1,3-dioxa-2-silacyclohexanes at the HF/pVDZ level, is a transition state rather than an intermediate minimum. The molecules of 2-sila- and 2-germa-1,3-dioxacyclohexanes exhibit an enhanced conformational flexibility as compared to the 1,3-dioxanes.     

Cyclocondensations of 3-alkylpyrazol-5-amines with 3-arylprop-2-enals and cyclic 1,3-diketones

Domino reactions of 3-alkylpyrazol-5-amines with 3-arylprop-2-enals and cyclic 1,3-diketones regioselectively afforded pyrazolo[3,4-b]pyridine derivatives. The alkylation and acylation of the synthesized compounds were studied using 3,7,7-trimethyl-4-[(E)-2-phenylethenyl]-2,4,6,7,8,9-hexahydro-5H-pyrazolo-[3,4-b]quinolin-5-one as model.