Studies on the reactions of fluoroalkanesulfonyl azide with aromatic compounds

The thermal decomposition reactions of fluoroalkanesulfonyl azides R_fSO₂N₃ (1) in the presence of various substituted benzene X_nC₆H_6−n [X: CH₃ (n=1, 2, 4, 6), OCH₃ (n=1, 2), C₆H₅CH₂ (n=1), F, Cl, Br] were studied in detail. The N-aryl fluoroalkanesulfonyl amides [R_fSO₂NHC₆H_5−nX_n] were produced as the major products. The ortho/para ratio resembled that of an electrophilic aromatic substituted reaction. An ionic π- or σ-complex was postulated as the intermediate for these reactions.     

A quantum chemical study of Cr(CO)3(B3N3H6 ? n F n ) (n = 1–3) complexes

The electronic structure and properties of Cr(CO)₃(B₃N₃H_{6 ? n} F _n ) (n = 1?C3) complexes have been explored using hybrid density functional B3LYP theory. Calculations indicate B-fluorinated isomers are more stable, and less polarizable, than N-fluorinated isomers. The aromatic natures of the borazine rings have been analyzed by nucleus independent chemical shift (NICS). The atoms in molecules (AIM) analysis indicates that Cr-C and Cr-N bonds distance is well correlated with the electron density of critical point (??_cp) in all species.     

Phase equilibria study of the (N-octylisoquinolinium thiocyanate ionic liquid + aliphatic and aromatic hydrocarbon,or thiophene) binary systems

Binary liquid + liquid phase equilibria for 8 systems containing N-octylisoquinolinium thiocyanate, [C₈iQuin][SCN] and aliphatic hydrocarbon (n-hexane, n-heptane), cyclohexane, aromatic hydrocarbon (benzene, toluene, ethylbenzene, n-propylbenzene) and thiophene have been determined using dynamic method. The experiment was carried out from room temperature to the boiling-point of the solvent at atmospheric pressure. For the tested binary systems the mutual immiscibility with an upper critical solution temperature (UCST) for {IL + aliphatic hydrocarbon, or thiophene} were observed. The immiscibility gap with lower critical solution temperature (LCST) for the {IL + aromatic hydrocarbon} were determined. The parameters of the LLE correlation equation for the tested binary systems have been derived using NRTL equation. The phase equilibria diagrams presented in this paper are compared with literature data for the corresponding ionic liquids with N-alkylisoquinolinium, or N-alkylquinolinium cation and with thiocyanate – based ionic liquids. The influence of the ionic liquid structure on mutual solubility with aliphatic and aromatic hydrocarbons and thiophene is discussed.     

Tuning of the molecular packing structure of comb-shaped polymer-grafted silica by using surface-initiated ATRP to enhance the molecular-shape selectivity towards polycyclic aromatic hydrocarbons

Poly(octadecyl acrylate)-grafted silicas were prepared by surface-initiated atom transfer radical polymerization (ATRP). Initially, undecyl ester and allyl ester-based ATRP initiators were synthesized and then immobilized on silica. The surface-initiated ATRP of octadecyl acrylate was carried out from the initiator-grafted silicas using copper(I) bromide and N,N,N′,N′,N′′-pentamethyldiethylenetriamine as catalyst precursors to produce poly(octadecyl acrylate)-grafted silicas, Sil-C₁₁-ODA_n (obtained from undecyl ester) and Sil-C₃-ODA_n (originated from allyl ester), respectively. Both Sil-C₁₁-ODA_n and Sil-C₃-ODA_n were characterized by DRIFT, suspension-state ¹H NMR, solid-state ¹³C CP/MAS NMR spectroscopies, thermogravimetric analysis (TGA), elemental analysis and differential scanning calorimetry (DSC) measurements. Suspension-state ¹H NMR, solid-state ¹³C CP/MAS NMR and DSC analyses suggest that Sil-C₁₁-ODA_n demonstrated more ordered structure than Sil-C₃-ODA_n. In this paper, it is also described that for ordering of the polymer phase is accompanied by the selectivity increase for the separation of poly cyclic aromatic hydrocarbons (PAHs) in RP-HPLC.     

Asymmetric syntheses of (R)-4-halo-6,6a,7,8,9,10-hexahydro-5H-pyrazino[1,2-a][1,n]naphthyridines,important 5-HT2C agonist precursors

Asymmetric syntheses of N-protected (R)-4-halo-6,6a,7,8,9,10-hexahydro-5H-pyrazino[1,2-a][1,n]naphthyridines, advanced intermediates for the synthesis of highly potent and selective 5-HT_2C agonists, are described. The key transformation involves ring opening of N-protected bicyclic sulfamidate (R)-hexahydro-3H-pyrazino[1,2-c][1,2,3]oxathiazine 1,1-dioxide with (4-halo-2-fluoropyridin-3-yl)lithiums or (3-bromo-5-fluoropyridin-4-yl)lithium. In situ hydrolyses of the resultant sulfamic acids and subsequent intramolecular nucleophilic aromatic substitutions (S_NAr) produce the enantiopure tricycles. The two step procedure represents new methodology for the stereoselective syntheses of tetrahydronaphthyridines.     

Facile preparation of aromatic esters from aromatic bromides with ethyl formate or DMF and molecular iodine via aryllithium

Various aromatic bromides were treated with n-BuLi and subsequently with ethyl formate, followed by the reaction with ethanol and molecular iodine in the presence of K₂CO₃ to provide the corresponding aromatic ethyl esters in good yields. Moreover, aromatic bromides could be transformed into the corresponding aromatic methyl esters in good yields by the treatment with n-BuLi and subsequently with DMF, followed by the reaction with methanol, molecular iodine, and K₂CO₃. Some aromatics could be also converted into the corresponding aromatic esters in good yields by the treatment with n-BuLi, and subsequently with ethyl formate or DMF, followed by the reaction with molecular iodine and K₂CO₃. The present reactions offer a novel route for the transition-metal-free, carbon-monoxide-free, and therefore environmentally benign one-pot conversion of aromatic bromides and aromatics into aromatic esters.     

Laser photolysis studies of spiropyran-merocyanine aggregate formation in solution

The photoinduced processes leading to formation of J-aggregate stacks of 1-(β-methacryloxyethyl)-3,3-dimethyl-6′- nitrospiro-(indoline-2,2′-[2H-[2H-1] benzopyran) d its associated ring opened merocyanine form B have been determined by N₂-laser transient spectroscopy. Detailed mechanisms for formation of complexes AB, A₂B, and J-aggregate stacks (A₂B) _n in aliphatic and aromatic solvents are presented.     

Synthesis and liquid crystal properties of a novel family of oligothiophene derivatives

In order to develop novel oligothiophene-based liquid crystals capable of hydrogen bonding, new terthiophene derivatives containing an alkylamide group, N,N′-dialkyl-5,5″-dichloro-2,2′:5′,2″-terthiophene-4,4″-dicarboxamide (DNC_nDCl3T, n=8, 18), N,N′-dialkyl-5,5″-dibromo-2,2′:5′,2″-terthiophene-4,4″-dicarboxamide (DNC_nDBr3T, n=5, 8, 16, 18), or N,N′-dialkyl-5,5″-diiodo-2,2′:5′,2″-terthiophene-4,4″-dica-rboxamide (DNC_nDI3T, n=8, 18), were designed and synthesized, and their thermal behaviour was examined. It was found that DNC₁₈DCl3T, DNC₁₈DI3T and DNC_nDBr3T (n=8, 16, 18) form a smectic A phase and that the alkyl chain length greatly affects liquid crystal phase formation. The absence of liquid crystallinity in the corresponding ester derivatives suggests that intermolecular hydrogen bonding also plays a role in the formation of a liquid crystal phases in the DNC_nDBr3T system.     

NMR studies of mixed-ligand iron(III) dithiocarbamates

¹H NMR studies of mixed-ligand iron (III) dithiocarbamates have been carried out using the following ligands: N,N-diethyldithiocarbamate, morpholinyl-N-, and piperidyl-N-carbodithioate. The ligand exchange equilibria gave all species of the general formula Fe(dtc)_n(dtc′)_3?n, where n = 0-3 with nearly random statistical distribution of Fe(Et₂dtc)_n(morphdtc)_3?n complexes. Magnetic moments of the mixed-ligand complexes have been determined. Both the magnetic moment and isotropic shift temperature dependences confirmed the cross-over properties of these mixed-ligand complexes.     

Quantitative Study of the Interaction between ATP and Aromatic Amines in Aqueous Solution

The interaction between adenosine-5??-triphosphate (ATP) and some aromatic amines (L), namely 1,2-phenylenediamine, 2-(2,4-diaminophenoxy)ethanol, 4-N-(2-hydroxyethyl)2,4-diaminoanisole, 4,5-diamino-1-N-(2-hydroxyethyl)pyrazole and 1,3-bis(2,4-diaminophenoxy) propane, was studied at T=298.15 K and I=0.06 mol?L^?1 in NaCl aqueous solution. For all of the investigated systems, the formation of [(ATP)(L)H _i ]^(i?4) species (i=1 to n+2; n=maximum protonation degree of the amine) with high yields (60?C80?%) were found. The ionic strength and temperature dependences of the complex formation constants were studied using semiempirical equations. The sequestering ability of the aromatic amines toward ATP was defined by calculating the pL₅₀ parameter (the total ligand concentration, as ?log₁₀ C _L, able to bind 50?% of ATP). The dependence of pL₅₀ on pH, ionic strength and temperature is reported. Moreover, it was found that the overall formation constants are reasonably linearly dependent on the number of protons in the complex species. Comparison with the stability of the species of analogous systems, such as ATP?Caliphatic amines and pyrophosphate?Caliphatic amines, is reported. For all these systems a fairly linear dependence was found of the formation constants on the basicity of the amines.     

Solvent Effect on Rotational Correlation Times of Symmetric Tetraalkylammonium Ions

The overall rotational correlation times of symmetric tetraalkylammonium ions, R ₄N⁺ (R = ethyl, n-propyl, n-butyl, and n-pentyl), in various solvents were determined by the measurements of the ¹³C NMR spin-lattice relaxation times and the nuclear Overhauser enhancement factors of each α-carbon, considering the contribution of the internal rotation around the N—C bond. Except in water, the observed solvent dependencies of the rotational correlation times, τ_r, showed good correlations with those predicted from an electrohydrodynamic (Hubbard–Onsager–Felderhof) model. The correlation times of R ₄N⁺ increased as the size of the alkyl groups became larger. In the case of the n-Bu₄N⁺ and the n-Pen₄N⁺ ion, the τ _r values were similar to or even higher than those predicted by the HOF model under the stick hydrodynamic boundary condition, in spite of the fact that the ions were too small to allow the solvent to be regarded as a hydrodynamic or a dielectric continuum. A comparison of the results with the rotations of other pseudotetrahedral ions, e.g., tetraphenylborate and tetraphenylarsenium ions and with the translation of the R ₄N⁺ ions suggests that a considerable part of the rotational friction for R ₄N⁺ is brought about by pushing aside the solvent in the spaces between the alkyl groups of R ₄N⁺. A significant slowing in the rotation in water was observed for the n-Pr₄N⁺, n-Bu₄N⁺, and n-Pen₄N⁺ions; the extent of this effect increased with increasing size of the alkyl group. The increase in friction was related to the hydrophobic hydration of the R ₄N⁺ ions.     

Observation and investigation of metastable decay series of (N2) n + cluster ions

N₂ cluster ions are produced by electron impact ionization of a supersonic N₂ cluster beam and analyzed with a double focussing sector field mass spectrometer. It is found that metastable N₂ cluster ions lose more than one N₂ molecule in the μs time regime and decay predominantly via sequential series (N₂) _n ⁺ *→(N₂) _n?1 ⁺ *→...→N ₂ ⁺ , evaporating a single monomer in each of these successive decay steps. The metastable decay rates determined in detail for cluster sizes 2≤n≤6 andn=20 lie between 1 and 10⁶s^?1. These rates(i) depend strongly on the time elapsed after ion formation and on the respective parent cluster ion size, and(ii) exhibit a quasiperiodic pattern in magnitude.     

Synthesis of 1,4,5-trisubstituted-1,2,3-triazoles by copper-catalyzed cycloaddition-coupling of azides and terminal alkynes

Primary, secondary, and aromatic azides undergo 1,3 dipolar cycloaddition-coupling with an excess of alkyne in the presence of Cu(CH₃CN)₄PF₆ as catalyst, N,N,N′-trimethylethylenediamine as ligand, molecular oxygen, and 4-methoxymorpholine N-oxide (NMO) as co-oxidant to afford 1,4,5-trisubstituted-1,2,3-triazoles.     

Enantioselective phenyl transfer to aldehydes using 1,1′-bi-2-naphthol-3,3′-dicarboxamide as chiral auxiliary

N,N,N′,N′-Tetra-n-butyl-BINOL-3,3′-dicarboxamide 5d was found to promote phenyl transfer from ethylphenylzinc to both aromatic and aliphatic aldehydes with high enantioselectivity up to 96% ee in tert-butyl methyl ether.     

Synthesis, characterization and intercalation property of layered zirconium benzylamino-N,N-dimethylphosphonate phosphate materials

Layered zirconium benzylamino-N,N-dimethylphosphonate phosphate (ZBMPA) was prepared by the reaction of zirconyl chloride with benzylamino-N,N-dimethylphosphonic acid (H₂BMPA) and phosphoric acid in the presence of hydrofluoric acid. The intercalation of n-alkylamines (n-butylamine, n-heptylamine and n-decylamine) into ZBMPA was primarily investigated at room temperature. These materials were characterized by elemental analysis, ICP, XRD, SEM, FT-IR, Raman spectra, TG and DSC. The composition of ZBMPA is Zr(HPO₄)(C₆H₅CH₂N(CH₂PO₃)₂)_0.5 · 2.0H₂O. The interlayer distance of ZBMPA, n-butylamine, n-heptylamine and n-decylamine intercalation compounds is 2.03, 2.58, 2.52 and 3.17 nm, respectively. ZBMPA and the n-alkylamine intercalation compounds are different in the morphology and vibration spectra. Thermogravimetries of all materials obtained reveal three step mass losses at temperatures of up to 1000 °C. These results indicate that n-alkylamines are intercalated into the galleries of host ZBMPA.     

Strong dependence of negative cluster ion spectra on principal quantum numbern in collisions of state-selected Ar** (n d) Rydberg atoms with N2O clusters

Electron transfer from state-selected Ar**(n d) Rydberg atoms to N₂O clusters has been studied over a broad range of principal quantum number (10 ≦n ≦ 45) and at two different Ar velocities (560 and 1000 m/s). A strongn-dependence of the negative cluster ion spectra is detected: while at highn ? 30, a rather narrow distribution of (N₂O) _q ·O^? and (N₂O) _q ^? ions around the major product (N₂O)₆·O^? is found, the distribution widens considerably towards largerq for decreasingn. Correspondingly, the effective rate constants for (N₂O) _q ·O^? and (N₂O) _q ^? formation show very differentn-dependences for lowq ≦ 6 and higherq. Possible reasons for the observed behaviour are discussed.     

Quantized losses from charged nitrogen clusters

Metastable decay of (N₂) _n ⁺ , formed in a supersonic jet and ionized by electron impact, has been analyzed forn≤50. The probability for decay of (N₂) _n ⁺ into (N₂) _n?x ⁺ , plotted versusx, exhibits pronounced oscillations. The “period” of these oscillations increases with increasing precursor sizen, but converges to an average value of approximately 4.7 beyondn=25.     

Composition of petroleum asphaltenes derived from ruthenium-catalyzed oxidation

Ruthenium ion-catalyzed oxidation of methanonaphthene oil (Krapivinskoye oilfield) revealed that its high molecular asphaltenes contain aromatic–aliphatic bridges and non- covalently bound (occluded) compounds. Covalently bound fragments are represented by C₅–C₁₈ n-alkanes, aromatic biphenyl-type structures, and naphthalenes located in the peripheral part of asphaltene molecules. Typical biological markers, i.e. terpanes, steranes, and n-alkanes have been identified among the occluded compounds.     

A practical approach to non-natural or N-unsubstituted α-arylglycine derivatives: Hf(OTf)4-doped Me3SiCl system-catalyzed aminomethylation of electron-rich arenes with a new type of N,O-acetal

The authors have demonstrated the Hf(OTf)₄-doped Me₃SiCl system-catalyzed aminomethylation of electron-rich aromatic compounds, such as indoles and anilines, with new types of N,O-acetals having a variety of functional groups, such as cyano, ester, bis(trimethylsilyl)amino, diallylamino, and cyclic amino moieties, for the preparation of non-natural aromatic amino acid derivatives. Aminomethylation using an N,O-acetal with a bis(trimethylsilyl)amino group was particularly successful in the direct preparation of an N-unsubstituted α-indolylglycine derivative, which required only a standard aqueous workup.