Structure and spectra of 1,3-dioxanes. II. Microwave spectrum, structural parameters, and ab initio calculations of 2-methyl-1,3-dioxane

The microwave spectra of five isotopomers with the ¹³C and ¹⁸O natural abundance isotopes of the 2-methyl-1,3-dioxane molecule (22–50 GHz) were studied. Rotational transitions of a and c types with 4 ≤ J ≤ 12 were identified. The rotational constants and the substitution r _s and effective r _o structural parameters of the molecule were determined. Ab initio calculations on 2-methyl-1,3-dioxane were performed with molecular structure optimization. The results of quantum-chemical calculations at different levels are compared with experimental data.     

Infrared spectra and rotational isomerization of 1-bromo-3-methyl-2-butene

Infrared spectra obtained for the title compound, (CH₃)₂CCH. CH₂Br, have revealed the co-existence of two rotational isomeric forms in the fluid phases, the geometrical structures of which cannot be ascertained by use of vibrational spectroscopy alone. The energy ditterence between the two isomers was found to be 1.1 kcal mol⁻¹ (mean value) in the liquid state. Some of the i.r. fundamental bands were assigned using the characteristic absorption frequencies of localized group.     

Structure and spectra of 1,3-dioxanes. microwave spectrum, structural parameters, and ab initio calculations of 5-methyl-1,3-dioxane

In the microwave spectrum of a 5-methyl-1,3-dioxane sample, the rotational transitions of a and c types with 4 ≤ J ≤ 11 for five isotopomers of a molecule with ¹³C and ¹⁸O isotopes in different sites are identified in a frequency range of 18 GHz to 42 GHz. The spectroscopic constants of isotopomers are found. The substituted r _s and effective r _o structural parameters of 5-methyl-1,3-dioxane are determined. By the B3PW91/aug-cc-pVDZ density functional method the equilibrium structure of the molecule is calculated. The results of quantum chemical calculations are compared to the experimental data.     

Preparation and coordination properties including catalytic activities of a bulky 2-methyl-3-thioxo-1,3-diphosphapropene

[reaction: see text] 2-Methyl-3,3-diphenyl-3-thioxo-1-(2,4,6-tri-tert-butylphenyl)-1,3-diphosphapropene, which bears a P=C-P=S skeleton, was prepared and used as a ligand of transition-metal complexes. The palladium complexes containing the ligated 3-thioxo-1,3-diphophapropene were stable and used for catalytic reactions such as cross-couplings and direct conversion of allyl alcohol to allylaniline.     

Synthesis of 2-R-1,3-dioxanes, derivatives of functionally substituted aldehydes of vanillin series

By the condensation of substituted aldehydes of vanillin series with 1,3-propanediol in boiling benzene in the presence of sulfo cation exchanger FIBAN K-1 as catalyst functionally 2-R-substituted 1,3-dioxanes were synthesized.     

Preparation and characterisation of some 4,4-dimethylbuta-1,3-dienone-transition metal carbonyls

(4,4-Dimethylbuta-1,3-dienone)iron tricarbonyl (IIa) is obtained in 70% yield from 3,3-dimethylcyclopropene (I) and nonacarbonyldiiron and in 17% yield from I and pentacarbonyliron. Analogously (4,4-dimethylbuta-1,3-dienone)-(η⁵-cyclopentadienyl)manganese carbonyl (V) is formed from I and (η⁵-cyclopentadienyl)(tetrahydrofuran)manganese dicarbonyl. Complexes IIa and V have been characterised by physical and chemical methods. Triphenylphosphine displaces one CO ligand from IIa to yield the corresponding triphenylphosphine-iron complex. The structure of IIa has been determined by X-ray diffraction.     

Preparation of 3-bromo-2-methylfuran and 4-bromo-2-methylfuran

4-endo-5-exo-Dibromo-3-methyl-3,6-endo-oxyperhydrophthalic anhydride 3b and 4-exo-5-endo-dibro-mo-3-methyl-3,6-endo-oxyperhydrophtbalic anhydride 3c were isolated from the bromo-adducts of 3-methyl-3,6-endo-oxy-1,2,3,6-tetrahydrophthalic anhydride 2. When 3b or 3c was heated in quinoline, only 3-bromo-2-methylfuran 4 was obtained from 3b and only 4-bromo-2-methylfuran 5 from 3c.     

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.     

Prephase state in 2-bromo-2-nitropropane-1,3-diol crystals: Structural aspects and IR spectra

This paper is a continuation of our series of publications dealing with crystal-lattice processes occuning on heating and at temperatures near the transition point and accompanied by structural changes in discrete molecules and in the crystal structure as a whole. The prephase state of 2-bromo-2-nitropropane-1,3-diol crystals and the transition from monoclinic to cubic phase are studied by IR spectroscopy at 296–391 K. Translated fromZnumal Strktumo, Chimii, Vol. 41, No. 2, pp. 294–299, March–April, 2000.     

2-Benzyl-2-methyl-2H-benzimidazole 1,3-dioxide derivatives: Spectroscopic and theoretical study

The spectroscopic behavior of 2-benzyl-2-methyl-2H-benzimidazole 1,3-dioxide derivatives in solution was studied in terms of electronic and nuclear magnetic resonance ((1)H and (13)C NMR) techniques. The experimental spectra were compared to the theoretical ones, obtained at DFT level, proving that the compounds adopt in solution a bird-like conformational distribution. Also, theoretically this conformational distribution resulted the most stable in gas phase. Infrared spectroscopy was used to study solid state behavior identifying experimentally the N-O stretching near to 1380, 1365 and 1225 cm(-1) and the vibrational benzimidazole skeleton near to 1610 and 1590 cm(-1). The vibrational spectrum was satisfactorily described by DFT calculations funding the N-O stretching as a coupled vibration near to 1470, 1350 and 1285 cm(-1). The fragmentation that takes place in mass spectrometry was assigned for all of the new derivatives.     

Synthesis and nonchair conformations of 2,2-disubstituted 4,4-dimethyl-1, 3-dioxanes

The fundamental possibility of the synthesis of 2-substituted 1,3-dioxanes by reaction of 1,3-dioxanium perchlorates with organometallic compounds is demonstrated. A method for the synthesis of acyl derivatives of heterocycles was developed on the basis of these compounds. The existence of 2,2,4,4-substituted 1,3-dioxanes in the twist conformation was shown by ¹H NMR spectroscopy; the twist conformation is explained by the effect of nonbonded 1,3-syn-axial interactions.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 9, pp. 1172–1179, September, 1978.     

Preparation of 1-aminomethylenemercapto derivatives of 2, 4, 6, 8-tetrathiaadamantane and adamantane

1-Aminomethylenemercapto derivatives of 3, 5, 7, 9, 9-pentamethyl-2, 4, 6, 8-tetrathiaadamantane and adamantane were obtained by aminomethylation of 3, 5, 7, 9, 9-pentamethyl-2, 4, 6, 8-tetrathiaadamantane-l-thiol and adamantane-1-thiol.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 5, pp. 658–660, May, 1976.     

Electron impact mass spectrometry of some 2-methyl-2-aryl- and 2-methyl-2-alkyl-1,3-dithianes

The electron impact mass spectrometric behaviour of four 2-methyl-2-aryl- and two 2-methyl-2-alkyl-1,3-dithianes is described and discussed in detail, with the aid of exact mass measurements, linked scans and mass-analysed ion kinetic energy spectrometry. The mechanism of the primary HS₂˙ loss, as well as those of the more unusual fragmentation pathways, are given.     

13C NMR spectra of 1,3-oxathiolane, 1,3-oxathiolane 3-oxide and 1,3-oxathiolane 3,3-dioxide derivatives

Carbon-13 nmr spectra of several 1,3-oxathiolane, 1,3-oxathiolane-3-oxide and 1,3-oxathiolane-3,3-dioxide derivatives are reported. Relationships between some stereochemical features and chemical shift are discussed.     

The mass spectra of some 4-arylhydrazono-3-methyl-2-pyrazolin-5-ones

The mass spectra of the title compounds, having various substituents on the aryl group are presented and discussed. High resolution mass measurements and metastable ions allow the fragmentation to be rationalized. The system is typified by the occurrence of intense molecular ions and of ions due to consecutive decomposition of the nitrogen-containing part of the molecule. Ions attributable to substituted, aniline-like fragments, and their decomposition products, are also abundant and may be used to identify the aryl group present.     

Reaction of 5-(1-bromo-2-aryl-vinyl)-3-methyl-4-nitro-isoxazoles and 1,3-dicarbonyl compounds

The preparation of E-5-(1-bromo-2-aryl-vinyl)-3-methyl-4-nitro-isoxazoles and their reaction with 1,3-dicarbonyl compounds to give cyclopropanes or dihydrofurans is described.