Zur synthese von siloxanen: II. Sterische substituentenkonstanten für siloxyreste

The acetolysis reactions of compounds of the type XSiMe₂Cl (I) with acetic acid in the presence of acetic anhydride were studied kinetically by means of ¹H NMR spectroscopy. We found these reactions exclusively influenced by steric effects (? = 0)The steric susceptibility constant (δ) of the acetolysis reaction, using alkylchlorodimethylsilanes was found to be 1.3. In this investigation the Taft E_s values showed a better correlation than the E_s(Si) values of Cartledge.From the rate constants of the acetolysis reactions with I (X = Cl, acetoxy or siloxy) we could then obtain for the first time E_s values for Cl, acetoxy and a series of siloxy groups at silicon.     

Hydrosilanes are not always a reducing reagent: a ruthenium-catalyzed introduction of primary alkyl groups to electron-rich aromatic rings using esters as a source of the alkyl groups

A triruthenium cluster, (μ₃, η², η³, η⁵-acenaphthylene)Ru₃(CO)₇ effectively catalyzes primary-alkylation reaction of electron-rich aromatic rings using a combination of hydrosilane and ester as a source of the primary-alkyl group. The reaction involves electrophilic substitution of arenes by carbocationic species stabilized by a neighboring alkoxy or siloxy group generated during the reduction of esters giving alkylated arenes after reductive removal of the alkoxy or siloxy group at the benzylic position.     

SOME MONOCYCLIC AND SPIROCYCLIC FLUOROPHOSPHORANES CONTAINING 6- AND 7-MEMBERED RINGS

Abstract

The reaction of 2,2-dimethyl-(1,8-naphtho[c,d])-1,3,2-dioxysilenin (3) and 2,2-dimethyldibenzo-1,3,2-dioxysilepin (4) with (C₆H₅)₂PF₃ gave the expected monocyclic fluorophosphoranes. Reaction of the same siloxy compounds with PF₅ gave products which could not be purified but whose ¹⁹F nmr spectra suggested that the desired spirocyclic compounds were present in the impure products. Reaction of the siloxy compounds with C₆H₅PF₄ did not yield identifiable products. The ¹⁹F nmr spectra of the products obtained are discussed and structures are tentatively assigned.     

A Stable Silanol Triad in the Zeolite Catalyst SSZ‐70

Nests of three silanol groups are located on the internal pore surface of calcined zeolite SSZ‐70. 2D ¹H double/triple‐quantum single‐quantum correlation NMR experiments enable a rigorous identification of these silanol triad nests. They reveal a close proximity to the structure directing agent (SDA), that is, N,N′‐diisobutyl imidazolium cations, in the as‐synthesized material, in which the defects are negatively charged (silanol dyad plus one charged SiO^? siloxy group) for charge balance. It is inferred that ring strain prevents the condensation of silanol groups upon calcination and removal of the SDA to avoid energetically unfavorable three‐rings. In contrast, tetrad nests, created by boron extraction from B‐SSZ‐70 at various other locations, are not stable and silanol condensation occurs. Infrared spectroscopic investigations of adsorbed pyridine indicate an enhanced acidity of the silanol triads, suggesting important implications in catalysis.     

A novel class of materials for ferroelectric liquid crystals containing siloxy chain end groups

Novel liquid crystals containing a siloxy chain as an end tail group instead of an alkyl chain were synthesized. The substitution effects were studied for ferroelectric liquid crystal materials. It was found that the temperature range for the chiral smectic C phase was reduced and shifted to lower temperature in comparison with the analogous alkyl chain derivatives. The crystallinity of the siloxy chain derivatives decreased and cholesteric phases were not observed. The influence of siloxy chains on ferroelectric liquid crystal properties, especially spontaneous polarizations and tilt angles, also greatly depended upon the mesogenic group structure. The X-ray diffraction results showed that the end tail group occupied a larger thickness in the chiral smectic C layer for the siloxy chain derivative than that for the alkyl chain derivative.     

Zur synthese von siloxanen: III. Induktive substituetenkonstanten für siloxyreste; 29Si-NMR-spektroskopische untersuchungen

For a series of siloxy groups at the silicon atom the inductive substituent constants σ^* and σ_I have been determined by means of ²⁹Si NMR spectroscopy.     

Regioselective Hydrosilylation of Olefins Catalyzed by a Molecular Calcium Hydride Cation

Chemo‐ and regioselectivity are often difficult to control during olefin hydrosilylation catalyzed by d‐ and f‐block metal complexes. The cationic hydride of calcium [CaH]⁺ stabilized by an NNNN macrocycle was found to catalyze the regioselective hydrosilylation of aliphatic olefins to give anti‐Markovnikov products, while aryl‐substituted olefins were hydrosilyated with Markovnikov regioselectivity. Ethylene was efficiently hydrosilylated by primary and secondary hydrosilanes to give di‐ and monoethylated silanes. Aliphatic hydrosilanes were preferred over other commonly employed hydrosilanes: Arylsilanes such as PhSiH₃ underwent scrambling reactions promoted by the nucleophilic hydride, while alkoxy‐ and siloxy‐substituted hydrosilanes gave isolable alkoxy and siloxy calcium derivatives.     

Silylotropy and the29Si NMR spectrum of 2-[dimethyl(pentafluorophenyl)siloxy]-2-penten-4-one

Conclusions ¹H,¹³C, and²⁹Si NMR spectroscopy was used to study the structure and silylotropy of 2-[dimethyl(pentafluorophenyl)siloxy]-2-penten-4-one. The temperature dependence of the²⁹Si NMR chemical shifts indicated the existence of an intermediate with pentacoordinated silicon.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 6, pp. 1424–1425, June, 1986.     

Brønsted acid-promoted cyclizations of siloxy alkynes with unactivated arenes, alkenes, and alkynes

In this article, we describe the development of a general concept for the development of new carbon-carbon bond-forming processes, which is based on Brønsted acid-mediated activation of a siloxy alkyne, followed by efficient interception of the resulting highly reactive ketenium ion by unactivated arenes, alkenes or alkynes. We found that trifluoromethane sulfonimide (HNTf₂) proved to be a superior promoter of these reactions compared to a range of other Brønsted acids. This finding could be attributed to a high acidity of HNTf₂ in aprotic organic solvents combined with a low nucleophilicity of the NTf₂⁻ anion. Depending on the nature of the nucleophile, the carbocyclizations proceeded either via 6-endo-dig or 5-endo-dig manifolds. In the case of 1-siloxy-1,5-diynes, the cyclizations occurred with a concomitant halide abstraction or arylation.     

New Tricyclic Amides. Synthesis,Structure, and Oxidation with Peroxyphthalic Acid

4-Azatricyclo[5.2.1.0^2,6]dec-8-ene was synthesized and brought into reactions with benzoyl, o-chlorobenzoyl, p-bromobenzoyl, p-, m-, and o-nitrobenzoyl, and bicyclo[2.2.1]hept-2-ene-endo-5,endo-6-dicarboximidoacetyl chlorides in chloroform in the presence of pyridine. The tricyclic amides thus obtained were epoxidated with peroxyphthalic acid prepared in situ by reaction of phthalic anhydride with a 35% aqueous solution of hydrogen peroxide. The structure of newly synthesized compounds was confirmed by IR and ¹H and ¹³C NMR spectroscopy and mass spectrometry. Their NMR spectra were compared with those of previously synthesized N-arylsulfonyl-4-azatricyclo[5.2.1.0^2,6]dec-8-enes on the basis of conformational composition of the corresponding p-nitrophenyl-substituted derivatives, which was determined by PM3 semi-empirical quantum-chemical calculations.__________Translated from Zhurnal Organicheskoi Khimii, Vol. 41, No. 6, 2005, pp. 837–845.Original Russian Text Copyright © 2005 by L. Kas’yan, Okovityi, Tarabara, A. Kas’yan, Bondarenko.     

Polyether azomethines. I. Synthesis and characterization

Six new polyether azomethines were synthesized by melt and solution polycondensation of six different diamines with 4,4′-[1,4-phenylene bis(oxy)] bisbenzaldehyde. The polymers synthesized by solution method are yellow to white in color and had inherent viscosities up to 0.59 dL/g in concentrated H₂SO₄. The polymers obtained by melt condensation show higher viscosity. Except polymer IV , others are insoluble in common organic solvents. The polymers were characterized by IR, x-ray, elemental analysis, and DSC study. The thermal stability of the polymers was evaluated by TGA and IGA study. Polymers I-III are highly thermally and thermooxidatively stable and exhibit no appreciable decomposition up to 420°C both in air and nitrogen atmosphere. It was shown that the curing of the polyazo-methines takes place by opening up of the ? CH?N? linkages at higher temperature. The electrical conductivities of the virgin and iodine doped polymers were as high as 10^?11?10^?16 and 10^?6?10^?8S cm^?1, respectively, at 30°C. Electronic spectra of the undoped polymers ( I-III ) indicated a large bathochromic shift of the ? – ?^* absorptions band (376 nm) due to ? C?N? bonds of the model compound. This can be attributed to extensive delocalization of the electrons along the polymer chain. © 1995 John Wiley & Sons, Inc.     

Design,Synthesis, and Biological Screening of Novel Anthranilic Diamides

Three series of new anthranilic diamide derivatives containing sulfide, N‐cyanomethylsulfilimine, and N‐cyanomethylsulfoximine groups were designed and synthesized by combining the active substructures of anthranilic diamides and sulfoxaflor. The structures of all newly synthesized compounds were confirmed by IR and ¹H/¹³C‐NMR, and some of them were confirmed by elemental analysis or HRMS too. The synthesized compounds were screened for their insecticidal and fungicidal activities. Bioasssay results indicated that some of the synthesized compounds possessed certain degrees of insecticidal activity against Mythimna separata. However, some compounds exhibited good fungicidal activity against Sclerotinia sclerotiorum.     

Synthesis, structures, physicochemical properties, and crystal-chemical systematics of M 2II AIIUO6 (MII = Pb, Ba, Sr; AII = Mg, Ca, Sr, Ba, Mn, Fe, Co, Ni, Cu, Zn, Cd, Pb) compounds

Pb₂A^IIUO₆ (A^II = Mg, Ca, Sr, Ni, Zn, Cd) compounds were synthesized by high-temperature reactions in the solid phase. For the Pb₂MgUO₆, Pb₂CaUO₆, and Pb₂CdUO₆ compounds, the crystal structures (space group P2₁/n) were refined by the Rietveld method. It was demonstrated that these structures belong to the perovskite structure type. Crystal-chemical systematics was performed for all synthesized perovskites. High-temperature X-ray diffraction and differential scanning calorimetry were used to study the thermal stability and phase transitions, determine the thermal expansion coefficients, and elucidate the effect of atoms located in octahedral and cuboctahedral positions on the heating behavior of the structure. The standard enthalpies of formation of the Pb₂A^IIUO₆ compounds were determined by reaction calorimetry.     

Synthesis,biological screening,in silico study and fingerprint applications of novel 1, 2, 4-triazole derivatives

A series of novel 1,2,4 triazole derivatives were synthesized by treating 4-bromo-2-(4H-1,2,4-triazole-3-yl)aniline (4) with different substituted benzene sulfonyl chlorides 5(a-f) and benzyl bromides 7(a-e) . IR, ¹H-NMR, ¹³C-NMR, and mass analysis confirmed the structures of the newly synthesized compounds. All derivatives were screened for their in vitro antibacterial activity against two bacterial strains viz Escherichia coli and Staphylococcus aureus, antifungal activity against Aspergillus flavus and Candida albicans, anthelmintic activity against Pheretima posthuma and also cytotoxicity activity against MDA-MB 231 and A375 cancer cell lines. It was found that some of the derivatives showed significant antibacterial, antifungal, anthelmintic, and cytotoxic activities when compared to respective standard drugs. Molecular docking studies have assisted the theoretical binding mode of the target molecules. Compounds were also explored for fingerprint application.     

Lactam and acid amide acetals 57. Synthesis,protonation, and acid-base properties of condensed derivatives of 4-oxo-1,4-dihydro-1,8-naphthyridine

A number of 4-oxo-1,4-dihydro-1,8-naphthyridine derivatives that differ with respect to the sizes of the azaand carbocycles were synthesized by the reaction of 3-amino-4-ethoxycarbonyl-5,6-dihydro-7H-pyrindine and 3-amino-4-ethoxycarbonyl-5,6,7,8-tetrahydroisoquinoline with N,N-dimethylacetamide diethylacetal and N-methylbutyrolactam, N-methylvalerolactam, and N-methylcaprolactam diethylacetals and subsequent cyclization of the intermediate amidines. It was established by UV and ¹H and ¹³C NMR spectroscopy that the protonation of these compounds takes place at the exocyclic oxygen atom. The dependence of the ionization constants of the compounds obtained in 70% DMFA on the size of the saturated cyclic fragments of the molecules was established.See [1] for Communication 56.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 5, pp. 643–651, May, 1990.     

Protonation,deuteration, and formylation of aceperidazylenes

1H-1,2-Diazaphenalene derivatives in which the pyridazine ring is ortho- and peri-fused to acenaphthene and acenaphthylene (1H-indeno[6,7,1-def]cinnolines) have been synthesized. It has been found that electrophilic attack on these compounds is directed at C⁶.     

Synthesis,structural characterization,and anion interactions of new triazole-linked urea derivative fully substituted cyclotriphosphazene compounds

Three novel fully substituted urea derivative cyclotriphosphazene compounds 5–7 were synthesized by alkyne-azide 1,3-dipolar cycloaddition reaction of propargyl substituted ureas 2–4 with hexaazide substituted cyclotriphosphazene 1 in the presence of Cu(I) catalyst. All compounds were characterized with spectroscopic techniques such as FT-IR, ¹H, ¹³C, and ³¹P nuclear magnetic resonance and mass spectroscopy. Also, the usefulness of compounds 5–7 as anion carriers was investigated by ¹H NMR spectroscopy. For this purpose, ¹H NMR spectra of compounds 5–7 were recorded in the presence of tetrabutylammonium fluoride in DMSO-d₆. It was determined, that the urea protons in the compounds interact with fluoride.     

Supercapacitor performance of activated carbon derived from rotten carrot in aqueous,organic and ionic liquid based electrolytes

In this work, we report the synthesis of porous activated carbon (AC). AC was derived from rotten carrot, at different values of activating temperature under inert atmosphere, employing chemical activation method and ZnCl₂ as activation agent. On the basis of results observed by surface area and pore size analysis, effect of activation temperature on synthesized AC was determined. Other material properties such as morphology, thermal stability, vibrational response, and crystal structure of prepared AC were studied using standard techniques of material characterization. Further, the electrochemical performance of synthesized AC was studied as an electrode, in aqueous, organic and ionic liquid based electrolyte. It was found that the synthesized AC based electrode exhibits highest specific capacitance (135.5?F?g^?1 at 10?mHz) in aqueous electrolyte and highest specific energy (29.1?Wh?kg^?1 at 2.2?A?g^?1) and specific power (142.5?kW?kg^?1 at 2.2?A?g^?1) in ionic liquid based electrolyte. This shows the suitability of synthesized material for use in energy storage applications.     

Synthesis,Tautomerism, and Antiradical Activity of Novel Pteridinetrione Derivatives

Synthesis of 1‐methyl‐6‐((2‐(aryl‐(heteryl‐))‐2‐oxoethyl) pteridine‐2,4,7(1H,3H,8H)‐triones via [4 + 2]‐cycloaddition of 1‐methyl‐5,6‐diaminouracil with ethyl 4‐aryl(heteryl)‐2,4‐dioxobutanoates is described in presented work. It was established that the reaction occurs regioselectively and proceeds under refluxing of starting compounds in acetic acid for 60 min. The structures of synthesized compounds were proven by complex of physicochemical methods including infrared, ¹H‐, ¹³C‐NMR spectroscopy, liquid chromatography–mass spectrometry, and electron impact–mass spectrometry. Based on the detail analysis of the correlational NMR spectral data (correlation spectroscopy, heteronuclear single quantum coherence, heteronuclear multiple bond correlation, and Nuclear Overhauser effect spectroscopy), it was determined that in dimethyl sulfoxide solution, the 1‐methyl‐6‐((2‐(aryl‐(heteryl‐))‐2‐oxoethyl)pteridine‐2,4,7(1H,3H,8H)‐triones exist in two tautomeric forms: ketone (A) and enol (B). It was also found that tautomeric behavior of aforementioned compounds in hexadeuterated dimethyl sulfoxide is sensitive to the nature of the aryl or heteryl substituent at the position 6 of ring. The electron donating groups shift equilibrium to the tautomer A, while electron withdrawing – to the tautomer B. The synthesized compounds were tested on antiradical activity. It was found that obtained compounds reveal radical scavenging activity comparable or higher than ascorbic acid.