Conformation and vibrational spectra of 1,5-hexadiyne (bipropargyl) and 1,5-hexadiyne-1,6-d2

The infrared spectra of 1,5-hexadiyne (bipropargyl) and 1,5-hexadiyne-1,6-d₂ as vapours, liquids, as solutes in various solvents and as crystalline solids at low temperatures and at high pressures have been recorded. Raman spectra were obtained for the liquids, including semiquantitative polarization measurements, and for the low temperature crystals.The data were interpreted in terms of two conformers, anti and gauche, in the vapour and liquid state and one, the anti, in the crystalline forms. A phase transition for 1,5-hexadiyne was observed at ca. 240 K. Both the high and low temperature crystals had molecules in the anti conformer.Interpretation of the spectra in terms of conformational equilibria was facilitated by a thorough vapour phase band contour analysis. With a few exceptions, all the vibrational fundamentals for both conformers were assigned and found to be in good agreement with results from normal coordinate calculations.     

Synthesis and structure of 5,5′-[(E,E)-2,5-diiodohexa-1,5-diene-1,6-diyl]bis(2,3-dichloro-4,4-dimethoxycyclopent-2-en-1-one)

Treatment of 2,3,5-trichloro-5-[(E)-2,3-diiodoprop-1-en-1-yl]-4,4-dimethoxycyclopent-2-en-1-one with SmI₂ in THF gives 5,5′-[(1E,5E)-2,5-diiodohexa-1,5-diene-1,6-diyl]bis(2,3-dichloro-4,4-dimethoxycyclopent-2-en-1-one) and its meso form at a ratio of 3:1.     

High-resolution electronic spectra and luminescence properties of some benzonaphthyridines at 77 K. absorption and fluorescence spectra of 1,5-, 1,6- a

Absorption and fluorescence spectra of 1,5-, 1,6- and 4,6-benzo[h]naphthyridines (BN) were examined in Shpolskii matrices and in n-butanol at 77 K. Vibrational analysis of quasilinear spectra of 1,6- and 4,6-BN in n-hexane matrices was performed. Calcula- tions of the electronic structure of the isomers examined were done using a modified INDO CI method. The results of the experiments and calculations prove the π, π^* state to be the lowest excited singlet state of 1,6- and 4,6-BN molecules; in 1,5-BN molecule the S₁ (n, π^*) state is strongly perturbed by the nearby s₂(π π^*) state.     

The conformation and vibrational spectra of 1,5-hexadiene-3-yne (divinylacetylene) and perchloro-1,5-hexadiene-3-yne (perchlorodivinylacetylene)

Infrared spectra of 1,5-hexadiene-S-yne (divinylacetylene) have been recorded in the vapour phase, in solution and in the amorphous and crystalline solid states at 90 K in the region 4000–4020 cm^?1. Correspondingly, IR spectra ofperchloro-1,5-hexadiene-3-yne (perchlorodivinylacetylene) as a melt, as a solute in various solvents and as a solid at 90 K have been obtained. Raman spectra of the two compounds were recorded in the liquid (molten) state including polarization measurements, and as crystalline solids at 90 K.The spectral data indicate that each compound exists as one conformer only in the various states of aggregation. In divinylacetylene the molecular symmetry appears to be anti (C_2h) while for perchlorodivinylacetylene the symmetry is either C_2v (syn) or C₂ (gauche). Vibrational assignments for the spectra of both molecules are presented and the values are compared with the results of normal coordinate analyses.     

Conformational analysis of mesocyclic polythioethers : Crystal and molecular structures of 1,4-dithiacycloheptane, 1,5-dithiacyclononane and 1,6-dithiacyclodecane

The crystal and molecular structures of 1,4-dithiacycloheptane (1,4-DTCH), 1,5-dithiacyclononane (1,5-DTCN), and 1,6-dithiacyclodecane (1,6-DTCD) have been determined by single crystal X-ray studies. These compounds crystallize in the space groups P2₁2₁2₁ (No. 19), P2₁/c (No. 14), and P2₁/n, respectively with a = 5.409(1), b = 10.883(2), c = 11.390(2) Å, Z = 4; a = 9.600(4), b = 12.378(8), c = 7.904(3) Å, /gb = 113.31(3)°, Z = 4; and a = 5.290(1), b = 12.853(3), c = 6.850(2) Å, β = 93.39(2)°, Z = 2, respectively. The nonhydrogen atoms were located using direct methods and the hydrogen atoms were found by Fourier difference maps. Full-matrix least-squares refinement led to conventional R factors of 0.0459, 0.0558 and 0.0314, respectively. The conformations adopted by 1,4-DTCH, 1,5-DTCN and 1,6-DTCD, in the crystalline slate, are twist chair (C₂ symmetry), twist boat chair (C₂ symmetry), and boat chair boat (C_2k symmetry), respectively. The transannular S-S distances are 3.583, 4.108 and 4.864 Å, respectively.     

Molecular modeling of ring-chain equilibria for the ring-opening cross-metathesis of cis,cis-1,5-dimethyl-cycloocta-1,5-diene with ethylene at T=298.15 K

The molecular modeling of ring-opening cross-metathesis of cis,cis-1,5-dimethyl-cycloocta-1,5-diene (1,5-DM-COD), cis,cis-1,6-dimethyl-cycloocta-1,5-diene (1,6-DM-COD) and cis,cis-cycloocta-1,5-diene (COD) with ethylene (ethenolysis) at T=298.15 K using the B3LYP/6-31G(d,p) level of theory reveals that ring-chain equilibrium constants are dependent on the nature of cyclic diene. The ring-chain equilibria for the ethenolysis of 1,5-DM-COD is completely shifted to the formation of monomeric 2-methyl-hexa-1,5-diene.     

Einfache Synthesen Von 1,5-Didesoxy-1,5-Imino-D-Glucit (1-Desoxynojirimycin) Und 1,6-Didesoxy-1,6-Imino-D-Glucit Aus D-Glucofuranurono-6,3-Lacton

ABSTRACT

1,5-Dideoxy-1,5-imino-D-glucitol (1-deoxynojirimycin) and 1,6-dideoxy-1,6-imino-D-glucitol were synthesised by simple sequences in seven and six steps, respectively, from D-glucofuranurono-6,3-lactone. Attempts to improve the yield of the crucial regio- and stereospecific introduction of azide into position 5 of suitable derivatives of this substrate are described.     

Synthesis of some new purine-related compounds: Regioselective one-pot synthesis of new tetrazolo[1,5-a]pyrimidine,pyrazolo[1,5-a]pyrimidine and pyrimido[1,6-a]pyrimidine derivatives

An easy and efficient route for the synthesis of some tetrazolo[1,5-a]-, pyrazolo[1,5-a]- and pyrimido[1,6-a] pyrimidine derivatives was described through the reaction of sodium salts of formyl ketones with 5-aminotetrazole, 5-aminopyrazole derivatives and 6-aminothiouracil, respectively. The antimicrobial screening of some derivatives of the prepared compounds has been achieved, and it exhibited a moderate activity against the tested microorganisms.     

Conformation and vibrational spectra of 1,5-hexadiyne (bipropargyl)

The infrared spectra of 1,5-hexadiyne (bipropargyl) as a vapour, liquid and crystalline solid and in several solvents have been recorded. Raman spectra were obtained for the liquid (including polarization measurements), the crystal and for several solutions.The data were interpreted in terms of two conformers, trans and gauche, in the vapour and liquid states and one, the trans, in the crystalline form. Interpretation of the spectra in terms of the conformational equilibria was not straightforward, and firm conclusions could not be drawn from the spectra alone. Vibrational assignments were made, supported by normal coordinate calculations.     

Synthesis of 2H-1,5-benzodioxepin and 2,5-dihydro-1,6-benzodioxocin derivatives via ring-closing metathesis reaction

The synthesis of various 2H-1,5-benzodioxepin and 2,5-dihydro-1,6-benzodioxocin derivatives is described. The key step involves the construction of seven- and eight-membered rings via ring-closing metathesis reaction.     

Vibrational analysis of substituted nitrobenzenes. I—Vibrational spectra,normal coordinate analysis and transferability of force constants of some chlorinated nitrobenzenes

The Raman and Fourier transform infrared spectra of 2,3-dichloro-, 2,4-dichloro-, 2,5-dichloro-, 3,4-dichloro-, 3,5-dichloro-, 2,3,4-trichloro-, 2,4,5-trichloro-, 2,4,6-trichloro-, 2,3,5,6-tetrachloro- and pentachloronitrobenzene were recorded. Raman polarization measurements were made wherever possible. A normal coordinate analysis was carried out for both the in-plane and out-of-plane vibrations of these molecules using a 59-parameter modified valence force field. The force constants were refined using an Overlay least-squares technique employing 352 frequencies of 10 molecules. The reliability of the force constants so obtained was tested by making a zero-order calculation for p-, m- and o-dinitrobenzenes, 1-fluoro-, 1-chloro- and 1-bromo-, 2,4-dinitrobenzenes, 2,4-difluoro- and 2,5-difluoro- and 2,5-dibromonitrobenzenes. Unambiguous vibrational assignments of all the fundamentals were made using the potential energy distribution and eigen vectors.     

trans-Stereoselective intramolecular crossed pinacol coupling of aromatic 1,4-, 1,5-, and 1,6-diketones by electroreduction

Electroreduction of aromatic 1,4-, 1,5-, and 1,6-diketones in the presence of chlorotrimethylsilane and triethylamine gave four-, five-, and six-membered 1,2-diols with trans-stereoselectivity.     

A nitro sugar mediated synthesis of 6-amino-1,5,6-trideoxy-1,5-imino-d-glucitol (6-amino-1,6-dideoxynojirimycin)

6-Benzoylamino-3-O-benzyl-1,5,6-trideoxy-N-(1,1-diphenylmethyl)-1,5-imino-d-glucitol 12a and its epimer 6-benzoylamino-3-O-benzyl-1,5,6-trideoxy-N-(1,1-diphenylmethyl)-1,5-imino-l-iditol 12b, the protected forms of 6-amino-1,6-dideoxynojirimycin 4 and its C-5 epimer 5, respectively, were easily prepared from diacetone-d-glucose via 6-O-benzoyl-3-O-benzyl-1,2-O-isopropylidene-5-C-nitromethyl-α-d-glucofuranose 7a or 6-O-benzoyl-3-O-benzyl-1,2-O-isopropylidene-5-C-nitromethyl-β-l-idofuranose 7b. 6-Amino-1,6-dideoxynojirimycin 4 (an important precursor of a wide range of glycosidase inhibitors) was easily prepared from 1,5-imino-d-glucitol 12a.     

SCF CI PPP study of the electronic structure of bromo derivatives of isomeric 1,5-, 1,6- and 4,6-benzo[h]naphthyridines

For six isomeric bromo 1,5-, 1,6- and 4,6-benzo[h]naphthyridines (bn) 1–6 and three dibromo derivatives 7–9, the electronic structure, wave number, oscillator strength values and dipole moments have been calculated by SCF CI PPP methods, also using the HMO approximation for comparison purposes. The calculated oscillator strength and wave number values were compared with the experimental data of ultraviolet spectroscopy; also comparison of the ultraviolet spectra of 1–9 with those of unsubstituted bn has been made. Plots of the calculated and observed wave number values of the investigated compounds show good correlation.     

Cycloaddition reactions of 1,5-, 1,6- and 4,6-benzo[h]naphthyridinium N-dichloromethylides with dimethyl acetylenedicarboxylate

Summary Cycloaddition reactions of 1,5-, 1,6-, and 4,6-benzo[h]naphthyridinium N-dichloromethylides with dimethyl acetylenedicarboxylate are reported. Ylides were formedin situ from corresponding benzo[h]naphthyridines and dichlorocarbene.

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Cycloadditionsreaktionen von 1,5-, 1,6- und 4,6-Benzo[h]naphthyridinium-N-dichloromethyliden mit Acetylendicarbonsäuredimethylester

Zusammenfassung Es wurden Cycloadditionsreaktionen von 1,5-, 1,6- und 4,6-Benzo[h]naphthyridinium-N-dichloromethyliden mit Acetylendicarbonsäuredimethylester untersucht. Die Ylide werdenin situ aus den entsprechenden Benzo[h]naphthyridinen und Dichlorcarben erhalten.

     

Conformational analysis of mesocyclic polythioethers : Gas phase conformational analysis of five mesocyclic polythioethers using photoelectron spectroscopy

The helium I photoelectron spectra of the mesocyclic polythioethers 1,4-dithiacycloheptane (1,4-DTCH), 1,5-dithiacyclooctane (1,5-DTCO), 1,5-dithiacyclononane (1,5-DTCN), 1,4,7-trithiacyclononane (1,4,7-TTCN), and 1,6-dithiacyclodecane (1,6-DTCD) are reported. The conformations of these molecules in the gas phase are deduced from correlations of the observed spectra with semi-empirical MO calculations, as well as molecular mechanics analysis.     

Naphthyridines. Part 3: First example of the polyfunctionally substituted 1,2,4-triazolo[1,5-g][1,6]naphthyridines ring system

Treatment of 1,2,4-triazoles (1) with diethylmalonate in bromobenzene gave 1,2,4-triazolo-[1,5-a]pyridines 2. Chlorination of 2 using POCl₃/DMF (Vilsmeier reagent) led to the isolation of 7-chloro-6-formyl-1,2,4-triazolo[1,5-a]pyridine derivative 4, which reacted with the stabilized ylid 5 to afford 6-ethoxycarbonylvinyl-1,2,4-triazolo[1,5-a]-pyridines 6. Azidation of 6 yielded the corresponding azido compound 7, (Scheme 2). Reduction of 7 with Na₂S₂O₄ gave the corresponding 7-amino compound 8, which cyclized in boiling DMF to give the novel 1,2,4-triazolo[1,5-g][1,6]naphthyridines 9. On the other hand, reacting 7 with one equivalent of PPh₃ (aza-Wittig reaction) in CH₂Cl₂ gave 7-imino-phosphorane derivative 10, and subsequent cyclization in boiling DMF afforded the new 1,2,4-triazolo[1,5-g][1,6]naphthyridine derivative 11 (Scheme 3). However, treatment of 10 with phenyl isothiocyanate in 1,2-dichlorobenzene at reflux temperature gave the new 1,2,4-triazolo[1,5-g][1,6]naphthyridine derivative 14 (Scheme 4). Refluxing 6 with excess of a primary amines 15a,b in absolute. EtOH yielded the corresponding 7-alkyl-amino-1,2,4-triazolo[1,5-a]pyridines 16a,b. These obtained amines 16a,b underwent intramolecular heterocyclization in boiling DMF to give the novel 9-alkyl-1,2,4-triazolo[1,5-g][1,6]-naphthyridines 17a,b, in excellent yields (Scheme 5).     

Conformation and vibrational spectra of 1-bromo-1,5-hexadiyne (bromobipropargyl)

The IR spectra of 1-bromo-1,5-hexadiyne (bromobipropargyl) as a vapour, liquid and crystalline solid and in several solvents have been recorded. Raman spectra were obtained for the liquid (including polarization measurements) and the crystal.The data were interpreted in terms of two conformers, trans and gauche, in the vapour and liquid states and one, trans, in the crystal. The conclusion that the trans conformer was the one present in the crystal was based on several independent pieces of evidence. Vibrational assignments were made, supported by normal coordinate calculations.     

Gallium(III) halide promoted synthesis of 1,3,5-triaryl- 1,5-dihalo-1,4-pentadienes

Aryl substituted alkynes undergo smooth coupling with aldehydes in the presence of gallium(III) halides under extremely mild conditions to afford the corresponding 1,3,5-triaryl-1,5-dihalo-1,4-pentadienes in good yields with E,Z-selectivity. Similarly 1,3,5-triaryl-1,5-dichloro-1,4-pentadienes are also obtained with niobium(V) chloride.