Preparation of polymers with substituted allyl end group using dimer of α-methylvinyl monomer as addition fragmentation chain transfer agent at high temperatures

The dimerization of methyl methacrylate, ethyl methacrylate, methacrylonitrile, and α-methylstyrene to 2-substituted-1-allylic compounds [CH₂?C(X)CH₂C(CH₃)₂X] (X = COOR, C₆H₅, or CN), and methyl α-ethylacrylate to a 3-substituted-2-allylic compound [CH₃CH?C(COOCH₃)CH₂C(CH₃)(C₂H₅) COOCH₃] was carried out by catalytic chain transfer using benzylbis (dimethylglyoximato) (pyridine) cobalt (III). These dimers were then used as addition-fragmentation chain transfer agents in the polymerizations of methyl methacrylate and styrene at 80⁰C or above. Cross-dimers from methacrylic ester-α-methylstyrene and methacrylonitrile-α-methylstyrene mixtures were similarly prepared. Except for those from methyl α-ethylacrylate and methacrylonitrile, all the dimers participated in the addition-fragmentation and the copolymerization to different extents. The dimer of methyl α-ethylacrylate was actually inactive during the styrene and methyl methacrylate polymerizations. The methacrylonitrile dimer was primarily incorporated in the polymer chain through copolymerization. Among the dimer and the cross-dimers from α-methylstyrene with the other monomers, those bearing the α-methylstyrene moiety in the α-substituent [CH₂?C(X)CH₂C(CH₃)₂C₆H₅, X?COOCH₃, COOC₂H₅, and CN] are noted as highly reactive chain transfer agents. © 1994 John Wiley & Sons, Inc.     

Electrosynthesis of esters of mono- and dioxoalkanoic and alkanedioic acids on the basis of nitro-substituted alkyl carboxylates and cycloalkanones

A one-pot electrochemical method for the synthesis of methyl monooxoalkanoates with the carbonyl group in position 4, methyl dioxoalkanoates with the oxo groups in positions 4,7-, 6,9-, 7,10-, and 12,15, and methyl 4-oxoalkanedioates was developed. This method is based on amperostatic electrolysis in an undivided cell of the salts of esters of nitroalkaniic acids and their adducts with CH₂=CHX (X = Ac, CO₂Me).     

Umsetzung von Arsolanen,Arsenanen und Arsepinen mit Oximen

Reaction of Arsolanes, Arsenanes, and Arsepines with Oximes The reaction of methyl-substituted arsolanes, arsenanes and arsepines with oximes results in it opening of the cyclic arsinous acid esters. In the course of the reaction of the substituted arsolanes (CH₂)₂O₂As? X[X = N(CH₃)₂, OCH₃, Cl] and (CH₂)₂ON(CH₃)As? N(CH₃)₂ with oximes the group X is substituted by the oxime; an opening of the rings does not take place.     

Bis(trimethylsilyl)-hypophosphit und Alkoxycarbonylphosphonigsäure-bis(trimethylsilyl)ester als Schlüsselsubstanzen für die Synthese von Organophosphorverbindungen

Bis(trimethylsilyl)hypophosphite und Alkoxycarbonylphosphonous Acid Bis(trimethylsilyl) esters as Building Blocks in Organophosphorus Chemistry The oxidation of pure bis(trimethylsilyl)hypophosphite ( BTH ) with chalcogenides forming (Me₃SiO)₂P(X)H (X = O, S, Se, Te) is described as well as its reactions with alkylhalides RX (X = Cl, Br, I) and Cl? C(O)OR (R = Me, Et, Bzl). By reaction with oxygen, sulfur, and selenium the alkoxycarbonylphosphonous acid bis(trimethylsilyl)esters form RO? C(O)? P(X)(OSiMe₃)₂ (X = O, S, Se) whereas with Cl? C(O)OR the bis(alkoxycarbonyl)-phosphinic acid trimethylsilylesters are obtained. After partial hydrolysis the resulting instable RO? C(O)? P(O)H(OSiMe₃) gives RO? C(O)? P(O)(OSiMe₃)? CH₂? NH? A? COOR′ (A = CH₂, CH₂CH₂, CHCH₃, CH₂CH₂SH, CHCH(CH₃)₂,…) when allowed to react with hexahydro-s-triazines of the aminoacid esters. Reactions of the alkoxycarbonyl-P-silylesters with NaOR or NaOH result in the corresponding mono-, di-, or trisodium salts. With mineral acids decarboxylation occurs, but H? P(O)(OH)? CH₂? NH? A? COOH can be obtained, too. The structure of the compounds described are discussed by their n.m.r. data.     

Site of protonation in the chemical ionization mass spectra of olefinic methyl esters

The H₂ and CH₄ chemical ionization mass spectra of the olefinic esters methyl acrylate, methyl methacrylate, methyl crotonate, methyl 3-butenoate, methyl 2-methyl-2-butenoate, methyl 3-methyl-2-butenoate and methyl cinnamate have been determined. In addition to the expected loss of CH₃OH from [MH]⁺, in many cases the protonated molecules also show loss of CO or CH₂CO with methoxy group migration to the positive ion centre, indicative of protonation at the double bond. These rearrangement reactions, which have analogies in electron impact mass spectra, result in chemical ionization mass spectra of isomeric molecules which show more substantial differences than the electron impact mass spectra. In the case of methyl cinnamate, isotopic labelling experiments show considerable interchange of the added proton with the ortho and meta phenyl hydrogens prior to CH₃OH or CH₂CO loss, although the extent of interchange is not the same for both cases.     

Formation of unsymmetrical cis-dialkyls of platinum(II) from platinum(II) hydroxo-complexes

The (hydroxo) methyl complex Pt(OH)(CH₃)(Diphos) [Diphos = Ph₂PCH₂CH₂PPh₂] reacts with compounds containing acidic CH bonds (HX) to give unsymmetrical cis-dialkyls of general formula Pt(CH₃)X(Diphos) [X = CH₂COCH₃, CH(COCH₃)₂, CH₂CN or CH₂NO₂]; both the methyl and the cyclohexenyl complexes Pt(OH)R(Diphos) (R = CH₃ or C₆H₉) insert carbon monoxide to give hydroxycarbonyl complexes PtR(CO₂H)(Diphos) which are remarkably stable to decomposition by β-elimination.     

Cyanide-Free One-Pot Synthesis of Methacrylic Esters from Acetone

Methacrylic esters, represented by methyl methacrylate (MMA), are widely used as commodity chemicals. Here, the one-pot synthesis of methacrylic esters from acetone, a haloform and alcohols in the presence of an organic base is described. Using DBU as the organic base for the reaction of acetone, chloroform and methanol in acetonitrile afforded MMA in 66 % yield. When the solvent was replaced by benzonitrile, the product MMA was successfully purified by distillation. Applicability of this process to various alcohols was also investigated to show ethyl, phenyl, CF₃CH₂, and n-C₆F₁₃CH₂CH₂ esters were obtained in moderate yields. The use of bromoform instead of chloroform resulted in the improvement of the yield, for example, methyl and n-C₆F₁₃CH₂CH₂ esters up to 81 and 70 %, respectively. The reaction with deuterated starting materials acetone-d₆ and MeOH-d₄, with DBU in acetonitrile afforded deuterated MMA (MMA-d₈) in 70 % yield.     

Alkoholyse von Tris(dimethylamino)-arsin

Alcoholysis of Tris (dimethylamino)arsine The reaction of tris(dimethylamino)arsine with alcoholes and thioles leads to the formation of esters of the general formula As(XR)₃ (X = O and S). The reaction is a suitable preparative method for the synthesis of the esters As(XR)₃ (X = O and S). By alcoholysis in steps results an equilibrium system containing the molecules AsX₃, AsX₂Y, AsXY₂, and AsY₃ (X = OR, Y = N(CH₃)₂).     

Potential energy distributions and normal coordinates of methyl,methyl-d3 and partially deuterated methyl chloride,bromide and iodide

The potential energy distributions and normal coordinates (L^?1 matrices) for twelve methyl halides, CH₃X, CH₂DX, CD₂HX and CD₃X (X = Cl, Br, I) have been calculated from known structural data. General harmonic force fields for methyl chloride, bromide and iodide previously determined from the most complete available isotopic frequency, Coriolis and centrifugal distortion data were used. The vibrational modes of these molecules are compared and discussed.     

Trivalent-pentavalente Phosphorverbindungen/Phosphazene. V. Darstellung,Eigenschaften und Reaktionen neuer Phosphonig- und Phosphinigsäureester

Trivalent-Pentavalent Phosphorus Compounds/Phosphazenes. V. Preparation, Properties, and Reactions of New Phosphonous- and Phosphinous Acid Esters Phosphonous diesters R? P(OR′)₂ (R ? CH₃, Ph and R′ ? CH₂? CF₃) have been synthetized by reaction of phosphonous dichlorides with 2, 2, 2-trifluoroethanol in the presence of a base. These diesters react with trimethyl(trimethylsilylimino)phosphorane, (CH₃)₃P?N? Si(CH₃)₃ by desilylation and N? P-linking to phosphinous acid esters (CH₃)₃P?N? P(OR′)R. The phosphinous acid esters react with methyl iodide to the quaternary salts [(CH₃)₃P? N? P(OR′)(R)CH₃]⁺I^?. The compounds are characterized by elementary analysis and spectroscopical methods.     

Darstellung und eigenschaften von triorganogermanium-, silicium- und -kohlenstoffsulfinsäurederivaten

A number of hitherto unknown sulfinic acid derivatives of germanium, silicon and carbon, R₃MO₂SR, were prepared by reaction of anhydrous aliphatic aromatic silver sulfinates, RSO₂Ag, with triorgano IVa element halides of the type R₃MX (R  aliphatic or aromatic group; M  Ge, Si, ;; X  Cl, Br). Their ester-like structure and the trigonal pyramidal configuration of the R₃M group result unequivocally from ¹H NMR, mass, IR and Raman spectroscopic investigations. The methyl esters (CH₃)₃MO₂SCH₃ (M  Ge, Si, C) are compared with the already known sulfinato complexes of tin and lead, (CH₃)₃SnO₂SCH₃ and (CH₃)₃PbO₂SCH₃.     

Reaction of organozinc reagents formed in reaction of dibromomalonic acid dialkyl esters and zinc, with 2-arylmethylenemalonic acid dinitriles and 3-aryl-2-cyanopropenoic acid methyl esters

Organozinc compounds, obtained from dibromomalonic acid dialkyl esters and zinc, react with 2-arylmethylmalonic acid dinitriles and 3-aryl-2-cyanopropenoic acid methyl esters forming 3-aryl-2,2-dicyanocyclopropane-1,1-dicarboxylic acid dialkyl esters and 3-aryl-2-cyanocyclopropane-1,1,2-tricarboxylic acid trimethyl esters. ¹H and ¹³C NMR, ³ J _CH constants are considered.     

Metallkomplexe mit biologisch wichtigen Liganden. CLVII [1] Halbsandwich‐Komplexe mit Isocyanoacetylaminosäureestern und Isocyanoacetyldi‐ und tripeptidestern („Isocyano‐Peptide”︁)

Metal Complexes of Biologically Important Ligands, CLVII [1] Halfsandwich Complexes of Isocyanoacetylamino acid esters and of Isocyanoacetyldi‐ and tripeptide esters (?Isocyanopeptides”?) N‐Isocyanoacetyl‐amino acid esters CNCH₂C(O) NHCH(R)CO₂CH₃ (R = CH₃, CH(CH₃)₂, CH₂CH(CH₃)₂, CH₂C₆H₅) and N‐isocyanoacetyl‐di‐ and tripeptide esters CNCH₂C(O)NHCH(R¹)C(O)NHCH(R²)CO₂C₂H₅ and CNCH₂C(O)NHCH(R¹)C(O)NHCH (R²)C(O)NHCH(R³)CO₂CH₃ (R¹ = R² = R³ = CH₂C₆H₅, R² = H, CH₂C₆H₅) are available by condensation of potassium isocyanoacetate with amino acid esters or peptide esters. These isocyanides form with chloro‐bridged complexes [(arene)M(Cl)(μ‐Cl)]₂ (arene = Cp*, p‐cymene, M = Ir, Rh, Ru) in the presence of Ag[BF₄] or Ag[CF₃SO₃] the cationic halfsandwich complexes [(arene)M(isocyanide)₃]⁺X^? (X = BF₄, CF₃SO₃).     

Metastable ion studies. 4—mass spectral fragmentation and isomerization in the esters of chlorinated propenoic acids

Metastable peaks have been used to study the fragmentation pathways of the methyl and trideuteriomethyl chloropropenoates and chloromethyl propenoate. The molecular ion peaks of the unsaturated esters are more intense than those of the saturated esters, α-Cleavage, [M? OCH₃]⁺, produces the base peak in almost all compounds, the relative abundances of the additional peaks being low for chloromethyl propenoate. The losses of H₂O, CH₃^. and COOH^. indicate the isomerization of some ionized chloro esters to the chlorinated 2-butenoic acid molecular ions. An intense loss of H₂O observed for methyl 2-chloropropenoate indicates its most facile isomerization, [ester]^+˙ → [acid]^+˙, whereas the isomerization in methyl trichloropropenoate could not be observed. The molecular ion of chloromethyl propenoate, however, also seems to partly rearrange to the chlorinated 3-butenoic acid ion, since the first field free region metastable peak shows a weak loss of CO. The new reaction pathways, i.e. the losses of CHO^˙, CH₂O and CH₂CO from ionized chloromethyl propenoate, were detected.     

The effect of molecular geometry on the fragmentation of methyl esters of cyclobut-3-ene-1,2-dicarboxylic acids

Elimination of CH₃OH from the molecular ions of the methyl esters of cyclobut-3-ene-1, 2-dicarboxylic acids under electron-impact occurs to a much greater extent in stereoisomers having a trans configuration than in the cis analogues. Deuterium labelling shows that this process takes place via different mechanisms in the stereoisomeric esters. The abundance ratio [M ? CH₃OH]^˙+/[M ? CH₃O]+ is suggested as the most sensitive criterion for the deduction of configuration in this system. Determination of the geometry of the cyclobutene esters by n.m.r. spectroscopy as well as by pyrolysis to corresponding isomeric muconates is also discussed.     

Conformational preferences of some substituted methyl groups in cyclohexanes as studied by carbon-13 nuclear magnetic resonance

Low temperature ¹³C NMR spectra of 80:20 mixtures of cis and trans-4? CH₃? CH₃? C₆H₁₀CH₂X, where ? C₆H₁₀-is 1, 4-disubtituted cyclohexyl and X=Br, CN, OH, OCH₃, Si(CH₃)₃, Sn(CH₃)₃, Pb(CH₃)₃ and HgOCOCH₃ have been recorded. The signals of the trans (e, e) components were assigned from the ambient temperature spectra of C₆H₁₁CH₂X and the established substituent effects of an equatorial methyl group in cyclohexane. Conformational equilibria of the cis (e, a?a, e) components were then computed from the intensities of the (remaining) signals (～180 K) of the two conformational isomers. From these equilibria A values of CH₂X were calculated, assuming additivity of conformational energies of CH₃ and CH₂X (the counter-poise approach). In general, these values are very similar to the value of the CH₃, although some trends do emerge. This study provides α, β, γ, and δ effects for a wide range of axial and equatorial ? CH₂X groups.     

Umsetzung von 2-Dimethylamino-(1,3,2)-diox-, oxathi- und dithi-arsolanen mit Alkoholen und Thiolen

Reaction of 2-Dimethylamino-(1,3,2)-diox-, oxathi-, and dithi-arsolanes with Alcohols or Thiols The reactions of 2-dimethylamino-(l, 3,2)-diox-, oxathi- and dithi-arsolanes (CH₂)₂XYAs? N(CH₃)₂ (X = Y = O or S; X = S, Y = O) with alcohols and thiols yield by cleavage of the As? N bond in the formation of alkoxy and alkylmercaptoarsolanes (CH₂)₂XYAs? ZR (X = Y = Z = O or S; X = Y: O, Z = S; X = Y = S, Z = O; X = S, Y = O, Z = O or S), respectively. Some of these arsolanes are not stable but rearrange under formation of 1,2-Bis-(arsolanyl)ethane and arsinous acid esters.     

Reaction of perfluoroalkanesulfonyl halide: 3. The reactions of perfluoroalkanesulfonyl bromide with α, β-unsaturated esters and chemical conversions of the products

The reactions of perfluoroalkanesulfonyl bromide with α, β-unsaturated esters were studied in detail. The reaction products were further converted to a series of perfluoroalkyl-substituted α, β-unsaturated acids or esters, α-amino acids and γ-lactones. A peculiar peak (M+15) was found to appear in the mass spectra of some perfluoroalkyl-substituted methyl esters. It was interpreted to be the result of a CH₃ group transfer to the molecular ion. Magnetic nonequivalence was observed in the ¹⁹F NMR spectra of CF₂ group linked to CH₂ in compounds 2f, g and 3f, g which showed a typical AB pattern, and was attributed to the effect of steric hindrance.     

Bimanes 28: Extraction of sulfur from fluorescent models for biological thiols

Sulfur extraction from the tripeptide thiol, glutathione (α-glu-cys-gly) ( 1 ) via reaction with syn-(1-bromo-ethyl, methyl)bimane ( 2 ) yields glutathione slfide and the thiabridged bimane, μ(S)-syn-(methylmethylene, methyl)bimane ( 3 ) [1]. The reaction with 2 has been extended to dithiols as models for important biological thiols such as reduced trypanothione. The fluorescent dithiols were derived through reductive cleavage with triphenylphosphine (tetrahydrofuan, Hcl−Kbr solution, pH 1.5) of the dithiatriclic bimane esters, μ(O₂C(CH₂)SS(CH₂)_nCO₂)-syn-(CH₂,CH₃)B, n = 1, 2, 3, prepared from syn-(bromomethyl, methyl)bimane ( 4 ) and the corresponding dithiadicarboxylic acids. Sulfur extraction led to 3 and the cyclic sulfide derived from the dithiol in moderate yields. The dithiols, dithiothreitol and dithioerythritol, also yielded moderate amounts of 3 . Sterically hindered thiols (e.g., those in hemoglobin) gave 3 in lower yields. Treatment of human red blood cells and red cells membranes (hemoglobin-free ghosts) with 2 gave rise to some 3 . A side product in some reactions was the oxabridged bimane, μ(O)-syn-(methylmethylene, methyl)bimane.     

Gas-phase protonation and methyl cation transfer from methyl halide ions

The ion-molecule reactions between [CH₃X]⁺˙ [CH₃XH] ⁺, [CH₃XCH₃]⁺ ions (X = F, Cl, Br, I) and a number of nucleophiles have been studied by ion cyclotron resonance techniques. Protonation of the nucleophiles is observed to occur from both the molecular ions [CH₃]X⁺˙ and protonated species [CH₃XH]⁺ whereas dimethylhalonium ions [CH₃XCH₃]⁺ react principally by methyl cation transfer. A notable exception occurs in methyl iodide where the molecular ions [CH₃I]⁺˙ act both as proton and methyl cation donors, whereas dimethyliodonium ions are found unreactive. The results are discussed with reference to the use of alkyl halides as reagent gases in chemical ionization experiments.