Systematische untersuchungen über das verhalten von organozinn-verbindungen gegenüber flüssigem schwefeldioxid : I. Reaktionen von tetraalkylstannanen mit flüssigem SO2

The SO₂ insertion into teraalkyltin compounds, R₄Sn (R = CH₃, C₂H₅, n-C₃H₇, i-C₃H₇, n-C₄H₉), was investigated depending on the presence of water, reaction temperature and reaction time. According to eqns. (1)–(5), the reaction products R₃SnO₂SR, R₂Sn(O₂SR)₂, (R₃Sn)₂SO₄, R₂SnSO₄ and R₂SnSO₃ were isolated. Especially; at low temperatures (<0°) the following order of decreasing reactivity of the teraorganostannanes toward SO₂ is established: R = C₂H₅ > CH₃ > n-C₃H₇ > n-C₄H₉ > i-C₃H₇     

The use of sulfines in nucleophilic acylation reactions

The thiophilic addition of MeLi and BuLi to aromatic alkylthio- and arylthio sulfines has been studied. The resulting dithioacetal monoxides are isolated in high yields. Reactions of MeLi with aromatic arylsulphinyland arylsulfonyl sulfines give the corresponding dithioacetal di- and trioxidcs. Acid treatment of dithioacetal monoxides results in aromatic aldehydes. The nucleophilic acylation of the acylanion equivalents obtained from sulfines is investigated. Alkylation of the dithioacetal monoxide anions, prepared in situ from MeLi and sulflnes of the type Ar(RS)CSO. with primary alkyl halides leads to dithioketal monoxide which upon acidolysis under anhydrous conditions are converted into vinylsulfides. The mechanism of the formation of the vinyl sulfides is discussed. The acylanion equivalents are acylated with benzoylchloride, CO₂ and benzaldehyde. The use of Cu¹ and 18-crown-6 as a catalyst appears to be crucial in some reactions. Michael additions of the dithioacetal monoxides to acrylonitrile are described.     

Properties of lithium tetraalkylborate complexes in adsorption and desorption of oxygen

Conclusions Lithium tert-butyltrialkylborates are capable of chemisorbing oxygen. The activation energy for thermal desorption of oxygen from [t-C₄H₉OB(OR)₃]Li·nO₂ at 298–548 K increases with decreasing degree of O₂ sorption and with increasing length of the alkyl substituent; for complexes with R=n-C₄H₉, n-C₇H₁₅, and n-C₁₀H₂₁, the values increase from 48.90 to 70.92 kJ/mole.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 2, pp. 251–253, February, 1989.     

Stepwise Engineering the Pore Aperture of a Cage-like MOF for the Efficient Separation of Isomeric C4 Paraffins under Humid Conditions

The separation of isomeric C4 paraffins is an important task in the petrochemical industry, while current adsorbents undergo a trade-off relationship between selectivity and adsorption capacity. In this work, the pore aperture of a cage-like Zn-bzc (bzc=pyrazole-4-carboxylic acid) is tuned by the stepwise installation methyl groups on its narrow aperture to achieve both molecular-sieving separation and high n-C₄H₁₀ uptake. Notably, the resulting Zn-bzc-2CH₃ (bzc-2CH₃=3,5-dimethylpyrazole-4-carboxylic acid) can sensitively capture n-C₄H₁₀ and exclude iso-C₄H₁₀, affording molecular-sieving for n-C₄H₁₀/iso-C₄H₁₀ separation and high n-C₄H₁₀ adsorption capacity (54.3 cm³ g⁻¹). Breakthrough tests prove n-C₄H₁₀/iso-C₄H₁₀ can be efficiently separated and high-purity iso-C₄H₁₀ (99.99 %) can be collected. Importantly, the hydrophobic microenvironment created by the introduced methyl groups greatly improves the stability of Zn-bzc and significantly eliminates the negative effect of water vapor on gas separation under humid conditions, indicating Zn-bzc-2CH₃ is a new benchmark adsorbent for n-C₄H₁₀/iso-C₄H₁₀ separation.     

Insect pheromones and their analogues. XVIII. Regiospecific synthesis of (±)-15,19-dimethyltritriacontane — A component of the pheromone of Stomoxys calcitrans

(±)-15,19-Dimethyltritriacontane (II) — a component of the pheromone of the stable fly — has been obtained by a five-stage synthesis from dimethylcyclooctadiene (I). The coupling of 1,1-dimethoxy-4-methyl-8-oxonon-4Z-ene [the product of the ozonolysis of (I)] with n-C₁₃H₂₇CH=PPh₃ (THF; ?30°, 2 h; 25°, 15 h; Ar) gave 1,1-dimethoxy-4,8-dimethyldocosa-4Z,8Z(E)-diene (III). The hydrolysis of (III) (TsOH·Py, H₂O-Ac, boiling, 4 h) gave the corresponding aldehyde (IV). The condensation of (IV) with n-C₁₀H₂₁CH=PPh₃ (THF; ?60° to ?30°C, 2 h, 25°C, 15 h) led to 15,19-dimethyltritriaconta-11Z(E),15Z,19Z(E)-triene (V), the exhaustive hydrogenation of which (ethanol, H₂, 5% Pd/C, 25°C) gave (II). The substance, the yield in %, and R_f values are given, respectively: (II), 95, 0.92; (III), 29, 0.74; (IV), 80, 0.72; (V) 50, 0.8. The IR and PMR spectra of compounds (II)–(V) and the mass spectra of (II) and (III) are given.     

Isomerisierung am Cyclotrisilazan-System – Lithiumsalze und Kontraktionsprodukte

Isomerisation of the Cyclotrisilazane System — Lithium Salts and Contraction Products 2,2,4,4,6,6-Hexamethyl- and 2,2,4,4,6,6-hexamethyl-1-trimethylsilyl-cyclotrisilazane ( 1, 2 ) react with n-C₄H₉Li to give the lithium salts 3 and 4 . At 30°C 4 isomerizes in solution to the cyclodisilazane 5 within 15 h. 4 reacts with Me₂SiF₂ to the substituted compound 6 , whose Li salt contracts yielding the coupled product 7 . 1,3-Bis(fluorodimethylsilyl)-2,2,4,4,6,6-hexamethylcyclotrisilazane isomerizes to the Li salt of the corresponding cyclodisilazane, which reacts with the half-molar quantity of SiF₄ to the Si? N? Si? N? Si bridged cyclodisilazane dimer 8 . The tendency of contraction of 4 is discussed on the basis of its crystal structure.     

Synthese,Charakterisierung und Kristallstrukturen von Tetraiodoferraten(III)

Preparation, Characterization, and Crystal Structures of Tetraiodoferrates(III) The extremely air and moisture sensitive tetraiodoferrates MFeI₄ with M = K, Rb and Cs have been synthesized by reaction of Fe, MI and I₂ at 300°C in closed quartz ampoules. The essentially more stable alkylammonium tetraiodoferrates NR₄FeI₄ with R = H, C₂H₅, n-C₃H₇, n-C₄H₉ and n-C₅H₁₁ can be obtained by reaction of Fe, NR₄I and I₂ in nitromethane. The Raman and UV/Vis-spectra of the black compounds show the existence of tetrahedral [FeI₄]^? ions in the structures. The crystal structure of the monoclinic CsFeI₄ (CsTlI₄ type, spgr P2₁/c; a = 7.281(1) Å; b = 17.960(3) Å; c = 8.248(2) Å; β = 107.35(15)°) is built up by tetrahedral [FeI₄]^? ions and CsI₁₁ polyhedra. The crystal structure of the orthorhombic (n-C₅H₁₁)₄NFeI₄ (spgr Pnna; a = 20.143(4) Å; b = 12.683(3) Å; c = 12.577(3) Å) contains tetrahedral [(n-C₅H₁₁)₄N]⁺ ions and [FeI₄]^? ions, respectively.     

Separation of unmodified α-amino acid enantiomers by reverse phase HPLC

Summary A novel chiral phase system is presented for the resolution of unmodified α-amino acid racemates which is composed of a reverse phase packing coated with N-alkyl-L-hydroxyproline (where alkyl is n-C₇H₁₅-, n-C₁₀H₂₁- and n-C₁₆H₃₃-) and a hydro-organic eluent containing copper(II)acetate. The factors controlling retention and enantioselectivity such as concentration of Cu(II)ion and pH of the eluent, addition of NH₄Ac to the eluent, type and content of organic solvent of hydro-organic eluent and column temperature were examined. The extremely high enantioselectivity observed (α up to 16) is assumed to be caused by a three site sorbate-sorbent interaction involving bidentate coordination of two amino acids to a Cu(II)ion and hydrophobic attractions between hydrocarbon side chains of amino acids and the n-octadecyl groups of the support. The efficiency and selectivity of the system permits resolution of up to 7 racemic amino acids into enantiomers within 35 minutes on a conventional HPLC apparatus. 13th publication in the series dealing with the ligand-exchange chromatography. Previous publication: ref. [1].     

Synthesis and properties of dicyclopentadienyltantalum hydride olefin compounds

Reactions of Cp₂TaCl₂ with RMgCl (R = n-C₃H₇, i-C₃H₇, n-C₄H₉, s-C₄H₉, n-C₅H₁₁ and C₅H₉) give tantalum hydride π-olefin complexes Cp₂Ta(H)L (L = C₃H₆, C₄H₈, C₅H₁₀ and C₅H₈). Two isomers of Cp₂Ta(H)C₃H₆ were obtained. The complexes are useful starting materials for the synthesis of other tantalum hydride species, e.g. Cp₂Ta(H)PEt₃ and Cp₂TaH₃.     

Simultaneous determination of thiols and disulfides by high-performance liquid chromatography with fluorescence detection

The proposed simultaneous determination of thiols and disulfides requires 4- (aminosulfonyl)- 7-fluor-2,1,3,-benzoxadiazole (ABD-F) as the pre-column derivatization reagent for thiols and ammonium 7-fluoro-2,1,3,-benzoxadiazole-4-sulfonate (SBD-F) for disulfides followed by chromatography. The thiols and disulfides in solution are treated with ABD-F at 60°C for 5 min in pH 9.3 borate buffer containing 1 nM disodium-EDTA. After removal of excess of ABD-F with ethyl acetate, the remaining disulfides in the aqueous phase are treated with SBD-F at 60°C for 20 min in the presence of tri-n-butylphosphine, a reducing agent. The ABD-thiols and SBD-thiols thus produced are separated by reversed-phase chromatography and detected by fluorimetry (380- nm excitation, 510 - nm emission). SBD-cystein, SBD-homocystein, ABD-homocysteine, ABD-cysteine, SBD-glu- tathione, ABD-homocystein, SBD-N-acetylcystein, ABD-glutatione and ABD-N-acetylcysteine are well separated by linear gradient elution from 0.15 M H₃PO₄/CH₃CN (96:4) to 0.15 M H₃PO₄/CH₃CN (85:15) over 30 min followed by isocratic elution with 0.15 M H₃PO₄/CH₃CN (85:15) fro 10 min. The detection limits for the derivatives are in the range 0.09–0.9 pmol. When the method was applied to the determination of thiols and disulfides in rat tissues, cystein (0.75 μmol g^-1) and cystine (0.62 μmol g^-1) were obtained in kidney and reduced glutathione (1.4–3.4 μmol g^-1) was observed in liver, spleen, heart and testicle.     

Untersuchungen an Polyhalogeniden. XXVII. Über Tetra(n-propyl)ammoniumpolyiodide (n-Pr4N)In mit n = 3, 5, 7: Darstellung und strukturelle Charakterisierung eines Triiodids (n-Pr4N)I3, eines Pentaiodids (n-Pr4N)I5 und eines Heptaiodids (n-Pr4N)I7

Studies of Polyhalides. 27. On Tetra(n-propyl)ammonium Polyiodides (n-Pr₄N)I_n with n = 3, 5, 7: Preparation and Crystal Structures of a Triiodide (n-Pr₄N)I₃, a Pentaiodide (n-Pr₄N)I₅, and a Heptaiodide (n-Pr₄N)I₇ [(n-C₃H₇)₄N]I₃, [(n-C₃H₇)₄N]I₅ and [(n-C₃H₇)₄N]I₇ have been prepared by the reaction of tetra(n-propyl)ammoniumiodide [(n-C₃H₇)₄N]I with iodine I₂ in ethanol. Their crystal structures have been determined by single crystal X-ray diffraction methods. The triiodide is built up from layers of the quarternary ammonium ions n-Pr₄N⁺ and from two independent differently packed centrosymmetric triiodide ions I₃^? which alternate with each other along [100]. The pentaiodide ion forms slightly puckered almost squared nets perpendicular [001] of iodide ions which are connected with four iodine molecules by secondary bonds. The meshes from twelve iodine atoms include the cations. The centrosymmetric Z-shaped heptaiodide ion is built up from a linear symmetric triiodide ion and two iodine molecules forming twisted rope ladders along [001] which are separated by stacks of cations.     

Ketene dithioacetal mediated synthesis of 1,3,4,5-tetrasubstituted pyrazole derivatives and their biological evaluation

Abstract

Ketene dithioacetal mediated chemo- and regioselective synthesis of a series of novel 1,3,4,5-tetrasubstituted pyrazole derivatives (4a-l) integrated with a bioactive indole nucleus was achieved by reacting substituted 2-(1-methyl-1H-indole-3-carbonyl)-3,3-bis-(methylthio)-acrylonitrile (2) and substituted phenyl hydrazine hydrochloride (3) in the presence of a catalytic amount of anhydrous K₂CO₃ under reflux conditions. The structures were ascertained by ¹H NMR, NOESY, ¹³C NMR, FT-IR, and HRMS data. In vitro cytotoxicity evaluation of the synthesized compounds against MCF 7 (breast carcinoma) and normal Vero (monkey kidney) cell lines revealed that the compound 5-(5-Bromo-1-methyl-1H-indol-3-yl)-1-(4-cyano-phenyl)-3-methylsulfanyl-1H-pyrazole-4-carbonitrile (4k) showed significant cytotoxicity against MCF 7 (GI₅₀ = 15.6 µM) with low cytotoxicity against normal Vero cell line. Most of the synthesized compounds were also found to possess excellent anti-inflammatory and antioxidant (DPPH, NO, H₂O₂ and SOR) potential.     

The first example of alpha-thiomagnesiums generated from dithioacetal monoxides with Grignard reagent; their properties and some synthetic applications

Dithioacetal monoxides were synthesized from aldehydes and cyclohexanone, and reaction of the dithioacetal monoxides with Grignard reagents was investigated. The dithioacetal monoxide synthesized from alkylaldehyde and 4-chlorobenzenethiol reacted with i-PrMgCl to afford the desired alpha-thiomagnesium in high yield. The generated alpha-thiomagnesium was found to be stable at room temperature and to be useful in organic synthesis. In contrast to this, the dithioacetal monoxides derived from benzaldehyde and cyclohexanone did not give satisfactory results.     

Reactions of alkylcobalt complexes containing a tetradentate nitrogen-donating ligand

The reactions of RCo(BDM1,3pn)(H₂O) with light, heat, acids, electrophiles and nucleophiles were studied. (HBDM1,3pn is a mononegative, tetradentate dioxime-diimine ligand formed by condensing 2,3-butanedionemonoxime with 1,3-propanediamine in a 2/1 molar ratio; R = CH₃, C₂H₅, n-C₃H₇, n-C₄H₉, and C₆H₃CH_2-) Pyrolysis and photolysis of the alkyl complexes result in a cobalt(II) complex (anaerobic conditions) along with alkenes and alkanes. The major organic products from solid state pyrolysis at 200°C or photolysis in water are CH₄ (R = CH₃), C₂H₄ (R = C₂H₅), C₃H₆ (R = n-C₃H₇), C₄H₈ (R = n-C₄H₉) and (C₆H₅CH₂)₂ (R = C₆H₅CH₂). No alkyl—cobalt bond cleavage occurs with acids or bases in most cases. Two exceptions are the reactions with 3 M HNO₃ at 25°C and with 1 M NaOH at 52°C. Electrophiles like I₂ cleave the alkyl—cobalt bond forming RI and Co^III (BDM1,3pn)I₂. Nucleophilic reagents (N^-) displace the H₂O trans to the alkyl group to form RCo(BDM1,3pn)(N), but do not dealkylate the alkyl complex under the reaction conditions studied.     

Formation Constant of Dialkyltin(IV)-N-(Alkyl)-2/3-mercaptoacetamide Systems

The thermodynamic formation constants of N-(alkyl)-2- and/or 3-mercaptoacetamides complexes with dimethyl-, diethyl-, and n-dibutyltin(IV) cations have been determined potentiometrically in a dioxane-water mixture (75% v/v) at 30 ± 0.1°C in μ = 0.1 M NaCl using the Irving-Rossotti method and refined by the least-squares method. The basicity of the ligands follows the order C₂H₅NHCOCH₂SH > n-C₃H₇NHCOCH₂SH > n-C₄H_gNHCOCH₂SH > C₂H₅NHCOCH₂CH₂SH > n-C₃H₇NHCOCH₂CH₂SH > n-C₄H_g- NHCOCH CH SH. For each ligand the stability order of dialkytin(IV) complexes decreases as follows: [Me₂Sn(IV)]²⁺ >[Et Sn(IV)]²⁺ > [n-Bu₂Sn(IV)]^2+. This order is consistent with the group electronegativities of [R₂Sn(IV)]²⁺ cations calculated from Sanderson's electronegativity scale.     

Structure of salts of substituted 2-alkylthiotetrahydropyrimidines

The structure and ring-chain tautomerism of 2-alkylthio-3,4,6,6-tetramethyl-4-hydroxy-3,4,5,6-tetrahydropyrimidine hydrohalides (Alk = CH₃, C₂H₅, n-C₃H₇, n-C₄H₉, iso-C₄H₉, CH₂C₆H₅ Hal = Cl, Br, I) were analyzed by means of UV, IR, and PMR spectroscopy. It is shown that the cations of the salts in the crystalline state and in solutions exist primarily in the cyclic form.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 5, pp. 695–698, May, 1982.     

Cyclic phosphites based on D-sorbitol and dulcitol

Conclusions Tricyclic triphosphites based on D-sorbitol and dulcitol with the general formula C₆H₈O₆(P-OR)₃, where R=C₂H₅-, n-C₃H₇-, and n-C₄H₉-in the case of sorbitol and R=C₂H₅ in the case of dulcitol, were synthesized for the first time.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 7, pp. 1666–1668, July, 1970.     

Chemoselectivity as a Delineator of Cuprate Structure in Catalytic 1,4‐Addition of Diorganozinc Reagents to Michael Acceptors

Reaction of the cyclic thioacetal (RS)₂CHCHO [R=1/2×? (CH₂)₃? ] with HCCCOMe, followed by treatment with TsCl/DABCO (Ts=tosyl, DABCO=1,4‐diazabicyclo[2.2.2]octane) affords the mono‐protected 1,4‐benzoquinone dithioacetal. The reactivity of this SR‐protected 1,4‐benzoquinone has been compared with the behavior of the analogous OR‐protected acetal in copper‐catalyzed additions of ZnMe₂ by using chiral phosphoramidite ligands. The activation energy for 1,4‐methylation of the latter OR‐acetals with ZnMe₂ (>95 % ee) has been determined for two CuX₂ pre‐catalysts (X=OAc, 12.2 kcal mol^?1; X=OTf, 6.7 kcal mol^?1; Tf=triflate). The dithioacetal SR aromatizes in the presence of Cu^I/ZnMe₂ giving 1,4‐HOC₆H₄S(CH₂)₃SMe through C? S bond formation. The disparate behavior of these two very closely related substrates is in accordance with the formation of closely related cuprate intermediates that were optimized by DFT calculations, supporting the synthetic and kinetic studies and thus defining the mechanisms of both pathways.     

Alcoholate Complexes of Nickel(II) Chloride

Alcoholate complexes of nickel chloride with the general formula, NiCL₂ · ROH (R = CH₃, C₂H₅, i-C₃H₇, n-C₄H₉, t-C₄H₉, t-C₅H₁₁, n-C₆H₁₃ and n-C₈H₁₇), synthesized either by the reaction of anhydrous nickel chloride with alcohols or by the replacement of methanol from NiCL₂ · MeOH with higher alcohols, depict interesting differences when R is a secondary or tertiary alkyl group instead of a primary group. A study of the magnetic susceptibility, thermogravimetric measurement, electron spin resonance and electronic reflectance spectra has been carried out to throw light on the structure of these derivatives.