Reaction of phenyl and 4-methylphenyl phenylethynyl sulfones with methyl acetoacetate

Stereoselective anti-addition of methyl acetoacetate at the triple C≡C bond of phenyl- and 4-methylphenyl phenylethynyl sulfones in the presence of sodium hydride yields the corresponding Michael adduct containing an impurity of arylsulfonylacetophenone. In the reaction with 4-methylphenyl phenylethynyl sulfone, methyl (Z)-2-acetyl-4-(4-methylphenylsulfonyl)-3-phenylbut-3-enoate was also obtained.     

Synthesis and reactions of methyl esters of 4-(3-r-sydnonyl)-2, 4-dioxobutanoic acid with bromine and p-tolyl azide

Chemistry of Heterocyclic Compounds -     

Thermal and acid-catalyzed transformations of 3<Emphasis Type="Italic">H</Emphasis>-pyrazoles obtained from diphenyldiazomethane and methyl phenylpropiolate

Reaction of diphenyldiazomethane with methyl phenylpropiolate in diethyl ether alongside the expected methyl triphenyl-3H-pyrazole-4-and-5-carboxylates (I and II) (38 and 24%) gave rise also to 8% of methyl 3,5-diphenyl-1-(1-ethoxyethyl)-1H-pyrazole-4-carboxylate. The main thermolysis product obtained from 4-methoxy-carbonyl derivative I was methyl 1,3,5-triphenyl-1H-pyrazole-4-carboxylate, whereas from regioisomer II formed predominantly methyl 4,4,5-triphenyl-4H-pyrazole-3-carboxylate and 1-methoxycarbonyl-2,3,3-triphenylcyclopropene that was a minor product of 3H-pyrazole I thermolysis. Addition of concn. H₂SO₄ to the solutions of methyl triphenyl-3H-pyrazole-4-and-5-carboxylates in AcOH resulted in fast regioselective isomerization of the 3H-pyrazole derivatives into the corresponding 4H-pyrazoles.     

Unusual ring transformations: Reaction of phenyl 7-fluoro-4-chromone-3-sulfonate with methyl 3-oxo-pentanoate in the presence of ammonium acetate

The novel benzoxathiinopyridines 4 and 5 , the hitherto unknown dibenzopyrone 6 and the heterocyclic enaminone 7 have been synthesized by ring transformations of phenyl 7-fluoro-4-chromone-3-sulfonate ( 1 ) with methyl 3-oxopentanoate ( 2 ) in the presence of ammonium acetate ( 3 ). The structures of 4–7 were determinated by spectroscopic methods and the reaction pathways of formation for these compounds are discussed.     

Infrared spectra of the CH3-MX and CH2-MHX complexes formed by reactions of laser-ablated group 3 metal atoms with methyl halides

Reactions of laser-ablated group 3 metal atoms with methyl halides have been carried out in excess of Ar during condensation and the matrix infrared spectra studied. The metals are as effective as other early transition metals in providing insertion products (CH3-MX) and higher oxidation state methylidene complexes (CH2-MHX) (X = F, Cl, Br) following alpha-hydrogen migration. Unlike the cases of the group 4-6 metals, the calculated methylidene complex structures show little evidence for agostic distortion, consistent with the previously studied group 3 metal methylidene hydrides, and the C-M bond lengths of the insertion and methylidene complexes are comparable to each other. However, the C-Sc bond lengths are 0.013, 0.025, and 0.029 A shorter for the CH2-ScHX complexes, respectively, and the spin densities are consistent with weak C(2p)-Sc(3d) pi bonding. The present results reconfirm that the number of valence electrons on the metal is important for agostic interaction in simple methylidene complexes.     

Divinyl aromatic compounds and Di(methacrylates) prepared by acid-catalyzed transformations of bis[4-(1-hydroxyethyl)phenyl]alkanes

The mechanism of formation of divinyl aromatic monomers including p,p′-divinyldiphenylmethane and 1,2-p,p′-divinyldiphenylethane and of their dimerization via terminal vinyl groups was studied. The factors affecting the structure, composition, and properties of thermosetting resins of a new class, Rolivsans, containing methacrylates of secondary aromatic alcohols (diols) and divinyl aromatic compounds with methylene bridges between benzene rings were examined.     

Alkylthio(4-methylpent-3-en-1-ynyl)carbenes: generation by the photolysis of 5-alkylthioethynyl-3,3-dimethyl-3H-pyrazoles and reactions with alkenes

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Preparation,structural characterization,and acid-catalyzed isomerization of 3-, 7-, and 9-benzyl-6-benzylthiopurines

Benzylation of 6-benzylthiopurine was examined. Structural assignments of the products were determined by 1-D and 2-D nmr spectroscopy (HMQC, HMBC, and nOe). In the presence of base, the isomeric N3-, N7-, and N9-benzylated products 4, 3 , and 2 were isolated; however, only 9-benzyl-6-benzylthio-purine ( 2 ) was obtained in the absence of base. In the latter case, the initially formed N3- and N7-isomers were, in the presence of acid, converted to 9-benzyl-6-benzylthiopurine ( 2 ) via a 6-benzylthiopurine intermediate as evidenced by analysis of the reaction over time using reversed-phase hplc.     

Kinetics of reactions between methoxycarbonyl,methyl, and methoxy radicals formed in flash photolysis of dimethyl oxalate in gas phase

Flash photolysis of dimethyl oxalate produced the radicals CH₃, CH₃O, and COOCH₃. Thermally equilibrated methoxycarbonyl radicals did not decompose during radicalradical reactions in the presence of 40-torr cyclohexane in the temperature range 298–448 K. Cyclohexyl radicals were also generated during the flash photolysis of the reaction mixture. Rate coefficients of radical–radical reactions were calculated from the amounts of stable products determined by gas chromatography: CO, CO₂, CH₄, C₂H₄, C₂H₆, CH₂O, CH₃OH, CH₃OCH₃, HCOOCH₃, CH₃COOCH₃, CH₃OCOOCH₃, CH₃C₆H₁₁, and CH₃OC₆H₁₁. Calculations were performed using an iterative computer integration program. Absolute values of rate coefficients were based on the rate coefficient of the reaction between methyl radicals, k₁ = 2.7 × 10¹⁰ dm³ mol^?1 s^?1, measured with the same equipment. The rate coefficients for reactions (5)–(8) are:      

Reactions of 3-isopropyl-, 3-isopropenyl-, and 3-acetyltropolone methyl ethers with guanidines. Synthesis of 9H-cyclohepta[d]pyrimidin-9-ones and cycloheptimidazoles

3-Isopropyl- and 3-isopropenyltropolone methyl ethers reacted with guanidine, 1-methylguanidine, and 1,1-dimethylguanidine to afford the corresponding 4-isopropyl- and 4-isopropenylcycloheptimidazoles 4a-f , respectively. The reactions of 3-acetyl-2-methoxytropones 2c-e with guanidines afforded 4-methyl-9H-cyclohepta[d]pyrimidin-9-ones 8a-i , while the reactions of 7-acetyl-2-methoxytropones 3c,d produced 4-acetylcycloheptimidazoles 4g-1 . From these reactions, several minor products were also isolated.     

Infrared spectra of CH3-MF and several fragments prepared by methyl fluoride reactions with laser-ablated Cu, Ag, and Au atoms

Reactions of laser-ablated, excited group 11 metal atoms with CH(3)F isotopomers have been carried out, leading to the generation of CH(3)-MF and CH(2)F-M complexes for Cu, Ag, and Au in addition to smaller complexes for gold. The products in the infrared spectra identified on the basis of their frequencies, isotopic shifts, and correlation with DFT calculated frequencies reveal that M-F insertion by the coinage metals and H atom release readily occur. The relatively low dissociation energies of CH(3)-AuF to give several smaller Au complexes are consistent with the observation of these fragments. The C-Au bonds of CF-AuH and CH(2)-AuF exhibit considerable π character, and the methylidene CH(2)-AuF contains a true double bond. In contrast, the bond orders of CH(2)-Au and CH(2)-AuH are lower, indicating that F bonded to Au contracts the gold 5d orbitals for better overlap with the carbon 2p orbital for π bonding.     

Stereochemistry in Lewis acid-catalyzed silylation of alcohols, silanols, and methoxysilanes with optically active methyl(1-naphthyl)phenylsilane

Stereochemistry in silylation reactions of alcohols, silanols, and methoxysilanes with optically pure (R)-methyl(1-naphthyl)phenylsilane were studied in the presence of Lewis acid catalysts. Tris(pentafluorophenyl)borane [B(C₆F₅)₃] was found to be highly reactive and stereoselective in the reactions. Optically active (R)-(alkoxy)methyl(1-naphthyl)phenylsilanes with 91–97% ee were produced from alcohols through the inversion stereochemistry of the silane. Stereoselectivity in the reaction with triphenylsilanol was moderate (64% ee). (R)-1,3-Dimethyl-1-(1-naphthyl)-1,3,3-triphenyldisiloxane with 94% ee was obtained from the silane with (methoxy)methyldiphenylsilane. The reaction with (R)-(methoxy)methyl(1-naphthyl)phenylsilane (88% ee) gave (R, R)-1,3-dimethyl-1,3-di(1-naphthyl)-1,3-diphenyldisiloxane [(R, R):(R, S):(S, S) = 87:12:0.5]. The stereochemistry was proved to almost completely inversion and retention for the chiral silicon centers of the silane and methoxysilane, respectively.     

Hydrogen-abstraction reactions from organosilicon compounds. The reactions of methyl,trideuteromethyl, trifluoromethyl,and ethyl radicals with tetramethylsilane

The following Arrhenius parameters have been determined for the hydrogen-abstraction reactions: R + (CH₃)₄Si → RH + (CH₃)₃SiCH₃

Hydrogen abstraction reactions from organosilicon compounds. The reactions of methyl,trifluoromethyl, and ethyl radicals with trichlorosilane

Arrhenius parameters have been determined for the hydrogen-abstraction reactions: R + SiHCl₃ + RH + SiCl₃

Composites of poly[4-((p-tolylimino)methyl)phenyl acrylate] and the Ni-complex with aminated MWCNT: Thermal,electrical and magnetic investigation

Abstract

Its nickel complex and a polyacrylate with side chain the Schiff base obtained from the condensation reaction of 4-hydroxybenzaldehide and p-toluidine, have been synthesized. The three-component composites were prepared using the polyacrylate, poly[4-((p-tolylimino) methyl) phenyl acrylate], its Ni-complex, and aminated MWCNT at three different percent (2%, 8% and 15% by wt). For characterization, FT-IR, 1H-NMR, SEM-EDX, SEM images and VSM (vibrating sample magnetometer) were used. The specific magnetic susceptibility for the Ni-complex is calculated as 3.0?×?10^?8 m³/kg from the slope of VSM straight line and the Ni-complex shows paramagnetic property. Thermal stabilities of the composites decreased compared with the polymer and Ni-complex. The AC conductivities of the samples increased with increasing frequency and increasing temperature. Frequency exponent of the equation connecting the AC conductivity to angular frequency was calculated as between 1.06 and 0.86 at 298?K and between 0.97 and 0.71 at 320?K, for all samples. Log σ_ac vs 1000/T straight lines were generated above and below the T_g temperature and the activation energies were calculated from the slopes as the values between 0.097 and 0.331?eV below Tg and the values between 1.134 and 0.768?eV above T_g.     

Kinetics of the reactions of halogenated methyl radicals (CF3, CF2Cl,CFCl2, and CCl3) with molecular chlorine

The kinetics of four gas-phase reactions involving halogenated methyl radicals (R ? CF₃, CF₂Cl, CFCI₂, and CCI₃) with molecular chlorine have been studied using a tubular reactor coupled to a photoionization mass spectrometer. The radicals were homogeneously generated by the pulsed photolysis of precursor molecules at 193 nm. The subsequent decays of the radical concentration were monitored in real-time experiments as a function of Cl₂ concentration to obtain the rate constants of these R + Cl₂ reactions. Where possible, the rate constants were measured as a function of temperature to determine Arrhenius parameters. Apparent discrepancies between these measured rate constants for CF₃ and CCl₃ with Cl₂ and ones obtained in prior indirect studies are explained. The higher activation energies for these R + Cl₂ reactions compared to that of the CH₃ + Cl₂ reaction are attributed in part to the different polarities of the transition states formed.