β-Ketoester — a Rearranged Product of Epoxidation of α, β-Unsaturated Methyl Ester

Attempted epoxidation of long-chain α,β-unsaturated esters resulted in the formation of the rearranged products of the corresponding epoxyesters. It was observed that reaction of peracids with esters of C₁₆, C₁₈ and C₂₂ trans-2-enoic acids, instead of yielding the expected epoxides, gave the isomerized products characterized as β-ketoesters. The structure of β-ketoester as saturated 3-oxoester was unambiguously established by chemical methods as well as by IR, NMR and Mass spectrometry. The selectivity of this rearrangement provides a useful synthetic pathway for the preparation of β-ketoesters.     

Darstellung von schwer entflammbaren polymeren unter verwendung von β-trichlormethyl-β-lactonen und deren derivate

By using β-trichloromethyl-β-lactones it is possible to incorporate the CCl₃-group into various classes of polymers. This can be achieved either via ringopening copolymerization or by using the adducts of these lactones with amines, alcohols or phenols in polycondensation or polyaddition reactions. Under suitable reaction conditions block- or graft-copolymers can be obtained. Finally, derivatives of β-trichloro-β-propiolactones can be used for the incorporation into polymers after or during polymerization. Polymers containing CCl₃-groups are flame resistant or selfextinguishing. Often, these effects are observed at lower chlorine contents than normally necessary with other chlorinated flame retardants.     

Optisch aktive O-Silyl-β-dicarbonylverbindungen. IV. Transsilylierungsreaktionen

Optically Active O-Silyl-β-dicarbonyl Compounds. IV. Transsilylation Reactions The relationship between the structure of O-silyl-β-dicarbonyl compounds and their tendency to transsilylation reactions is studied by gas chromatography. It is shown that the silyl derivatives of β-diketones and β-dicarboxylic acid diesters easily undergo intermolecular mutual transsilylation reactions. The same compounds quickly transfer silyl groups to free β-dicarbonyl compounds. On the contrary, with silyl derivatives of β-keto esters, o-acylphenols and salicylic acid esters no transsilylation reaction could be observed, and the transfer of silyl groups from O-silyl-β-keto esters to free β-keto esters is only very slow. The ease of transsilylation reactions of O-silyl-β-dicarbonyl compounds correlates with the velocity of racemization of optically active O-silyl-β-dicarbonyl compounds of the same structure. Therefore, we assume that intermolecular transsilylation reactions with inversion of configuration are the main reason for the racemization of optically active O-silyl-β-dicarbonyl compounds. However, no connection could be found between the tendency to transsilylation reactions and the stereochemistry of the reactions of optically active O-silyl-β-dicarbonyl compounds with LiAlH₄ which is also dependent on the structure of these compounds.     

Studies of the Ramberg-Bäcklund Rearrangement. Part I. Rearrangement of α-Bromo-β-Keto- and α-Bromo-α-Carbethoxy-Sulphones

α-Bromosulphones, carrying negative substituents (keto or carbethoxy-groups) next to the bromine atom, undergo the Ramberg-Bäcklund rearrangement and give α,β-unsaturated ketones and esters. β-Disulphones are converted into α, β-unsaturated sulphones under these conditions.     

Trans- α, β-ungesättigte Fettsäuren und deren Reduktionsprodukte mit Lithium-Aluminium-Hydrid und Diisobutyl-Aluminium-Hydrid

Trans-α,β-Unsaturated Fatty Acids and Products formed by their Reduction with Lithium-Aluminium-Hydride and Di-isobutyl-Aluminium-Hydride A method for the preparation of pure methyl esters of α,β-unsaturated fatty acids is described. The reduction of these esters with LiAlH₄ led to poor yields of α,β-unsaturated alcohols. Saturated alkanols and aldehydes were mainly formed. Di-isobutyl aluminium hydride gave near quantitative yields of α,β-unsaturated alcohols. The reaction was studied with the help of gas chromatography using strongly polar stationary phases.     

The Reaction of α,β-Unsaturated Ethyl Esters with Vinylmagnesium Chloride

While the reaction of linear α,β-unsaturated ethyl esters with vinylmagnesium chloride yields vinyl ketones as the main product, the reaction of substituted α,β-unsaturated ethyl esters yields triethylenic carbinols.     

Efficient Synthesis of β,γ‐Alkynyl α‐Amino Acid Derivatives by Ag(I)‐Catalyzed Alkynylation of α‐Imino Esters

The first catalytic synthesis of β,γ‐alkynyl α‐amino acid derivatives was achieved by direct addition of terminal alkynes to α‐imino esters in the presence of an Ag(I) salt under mild reaction conditions.     

β-Fur-2-yl-α-halogenacrylonitrile. VII. Reaktionen von β-(5-Brom-fur-2-yl)-α-bromacrylonitril mit Mercaptan,Thioharnstoff und Thioharnstoffderivaten

β-Fur-2-yl-α-halogenacrylonitriles. VII. Reactions of β-(5-Bromo-fur-2-yl)-α-bromoacrylonitriles with Mercaptans, Thiourea and Thiourea Derivatives β-(5-Bromo-fur-2-yl)-α-bromoacrylonitrile 1 reacts with ethylmercaptan to yield β-(5-bromo-fur-2-yl) β-ethylthioacrylonitrile 3 . With thiourea β,β′-thio-bis[β-(5-bromo-fur-2-yl)]-acrylonitrile 2 is formed. The pyrimidines 4 and 5 have been prepared by the reaction of 1 with s-methylthiourea and 2-aminothiazole, respectively. The structure of the new compounds were determined by means of x-ray analysis, ¹H-n.m.r., ¹³C-n.m.r. and mass-spectroscopy.     

Die UV-Spektren α,β-ungesättigter Ester und ihre Beeinflussung durch Lösungsmittel und Komplexbildung

UV Spectra of α,β-Unsaturated Esters and the Influence of Solvents and Complex Formation Positions and intensities of partially overlapped π-π* and n-π* transitions in spectra of methyl and ethyl esters of acrylic, methacrylic and crotonic acid are discussed. Reproducible values were determined by graphical and mathematical band-separations. n-π* bands in gaseous methyl acrylate show vibrationally fine structures. These are compared with fine structures in the spectra of α-methylene-γ-butyrolactone and α, β-dehydrobutyrolactone. In solutions with C_ester lt; 0,1 m self-associations are negligible. The transition-displacements Δv _max due to solvent effects closely correlate with the solvent parameters of KOSOWER . These correlations allow to calculate λ_max-values at which solvents absorb strongly. Equilibrium constants K of EDA-complexes with TCNE and chloranile were determined. With a competition method K was found in the range of 0.9 to 10.3 l · mol⁻¹.     

Synthesen von β-Fur-2-yl-α-halogenacrylonitrilen

Syntheses of β-Fur-2-yl-α-halogenacrylonitriles Syntheses of β-fur-2-yl-α-halogenacrylonitriles 2a–f by Wittig-olefination of furfurales, Hunsdiecker-reaction of β-(5-nitro-fur-2-yl)-α-cyanoacrylic acid 3 , halogenation of β-fur-2-yl acrylonitriles and reaction of furfurales with β-azido-α-halogen-γ-methoxy-Δ^α,β-crotonolactones 9 are described.     

Organocatalytic Asymmetric Aldol Reaction of Ketones with β,γ‐Unsaturated α‐Keto Esters: An Efficient Access to Chiral Tertiary Alcohol Skeletons

This update describes a highly efficient organocatalytic aldol reaction of ketones and β,γ‐unsaturated α‐keto esters for constructing the chiral tertiary alcohol motif. With the application of 9‐amino(9‐deoxy)epi‐Cinchona alkaloid and an acidic additive as catalysts, both acyclic and cyclic ketones react with β,γ‐unsaturated α‐keto esters smoothly to afford aldol adducts in good to excellent yields and asymmetric induction. This protocol offers a new pathway for the construction of adjacent chiral carbon centers and the synthesis of chiral β‐hydroxy carbonyl compounds.     

Photoelectrochemical phenomena at the interface Cu/Cu(II), glycine, α- or β-alanine

The analysis of photopotentials and photocurrents induced by laser beam perturbation of the interface Cu/solution of Cu(II)—glucine, α- or β-alanine complexes, has shown that phase layers containing Cu₂O display the properties of p-type semiconductors, except for the β-alanine system which displays n-type conductivity. In accordance with results of the analysis of thermodynamic and kinetic stability of Cu₂O layers the highest level of photoresponse is observed in the β-alanine system. Inversion of the photocurrent sign has been registered in the latter system at a certain cathodic overvoltage, the value of which depends on both the pH of solution and the laser emission intensity.     

Untersuchungen zur Bromierung/Dehydrobromierung von 17α-Cyanmethyl-17β-hydroxy-östr-5(10)-en-3-on

Investigations on the Bromination/Dehydrobromination of 17α-Cyanomethyl-17β-hydroxy-estr-5(10)-en-3-one Bromination/dehydrobromination of 17α-Cyanomethyl-17β-hydroxy-estr-5(10)-en-3-one 1a in the presence of pyridine leads to 17α-cyanomethyl-17β-hydroxy-estra-4, 9-dien-3-one 2a . The reaction was studied in various solvents with several bromination agents. Intermediates and byproducts of the reaction were isolated and their structures elucidated.     

Highly Enantioselective Michael Addition of Cyclic 1,3‐Dicarbonyl Compounds to β,γ‐Unsaturated α‐Keto Esters

A highly enantioselective Michael addition of cyclic 1,3‐dicarbonyl compounds to β,γ‐unsaturated α‐keto esters catalyzed by amino acid‐derived thiourea‐tertiary‐amine catalysts is presented. Using 5 mol% of a novel tyrosine‐derived thiourea catalyst, a series of chiral coumarin derivatives were obtained in excellent yields (up to 99%) and with up to 96% ee under very mild conditions within a short reaction time.     

Cascade Reactions: Sequential Homobimetallic Catalysis Leading to Benzofurans and β,γ‐Unsaturated Esters

The concatenation between a Pd(0)‐promoted deallylation catalytic cycle and a Pd(II)‐promoted heterocyclization catalytic cycle (an example of what we have named “sequential homobimetallic catalysis”) has been shown to occur starting from 1‐(2‐allyloxyphenyl)‐2‐yn‐1‐ols 1 to afford 2‐benzofuran‐2‐ylacetic esters 2 and β,γ‐unsaturated esters in high yields under carbonylative conditions. In view of the conceptual as well as the synthetic importance of the process, the mechanistic aspects and the synthetic scope of the reaction have been investigated in detail. All the experimental evidence is in agreement with the sequential homobimetallic mechanism, and the reaction has proven to be of general synthetic applicability.     

β-Fur-2-yl-α-halogenacrylonitrile. I. Darstellung von β-Fur-2-yl-ß-aminoacrylonitrilen und β-Fur-2-yl-α-aminoacrylonitrilen

β-Fur-2-yl-α-halogenacrylonitriles. I. Preparation of β-Fur-2-yl-ß-aminoacrylonitriles and β-Fur-2-yl-α-aminoacrylonitriles β-Fur-2-yl-α-halogenacrylonitriles 1 react with secondary amines to yield β-fur-2-yl-ß-aminonitriles 2 and β-fur-2-yl-α-aminoacrylonitriles 3 . The ¹ H-n.m.r. spectra of the E/Z isomers are discussed.     

β-Fur-2-yl-α-halogenacrylonitrile. IV. Reaktionen von β-Fur-2-yl-α-halogenacrylonitrilen mit Alkoholen und Phenolen

β-Fur-2-yl-α-halogenacrylonitriles. IV. Reactions of β-Fur-2-yl-α-halogenacrylonitriles with Alcohols and Phenols β-Fur-2-yl-α-halogenacrylonitriles 1a – c react with alcohols and phenols to yield β-fur-2-yl-β-alkoxyacrylonitriles and β-fur-2-yl-β-aroxyacrylonitriles 2a – k respectively. With ethylene glycol α-[2-(fur-2-yl)-1, 3-dioxolan-2-yl]acetonitriles 3a, b are formed.     

β-Fur-2-yl-α-halogenacrylonitrile. VIII. Konformationsuntersuchungen an substituierten β-Fur-2-yl-acrylonitrilen

β-Fur-2-yl-β-halogenacrylonitriles. VIII. Investigations of the Conformation of Substituted β-Fur-2-yl-acrylonitriles X-ray analysis, n.m.r.-investigations in the presence of Eu(FOD)₃ and NOE-measurement indicate, that the E-isomer of β-substituted β-fur-2-yl-acrylonitriles exist in the s-cis conformation, whereas the E-isomer of the α-substituted β-fur-2-yl-acrylonitriles prefer the s-trans-conformation. The influence of the configuration and conformation on the chemical shift of the H-3-furan protons is discussed.     

Synthesis and Properties of Monoazo Disperse Dyes Derived from 3-Amino-5-nitro[2,l]benzisothiazole

Disperse dyes based on 3-amino-5-nitro[2,1]benzisothiazole have been synthesised, using as coupling components derivatives of some alkyl esters of N-benzyl-N-phenyl-β-alanine and N-(β-phenylethyl)-N-phenyl-β-alanine. IR and visible spectra of the dyes were investigated and basic fastness properties were also determined. The lightfastness of the dyes was also studied in relation to mass spectral data.     

Zur Synthese CF3-substituierter Chinoline aus β-Chlor-β-trifluormethyl-vinylaldehyden. I

Synthesis of CF₃-Substituted Quinolines from β-Chloro-β-trifluoromethyl-vinylaldehydes. I 3-(Trifluoromethyl)-acroleines 2 have been synthesized through VILSMEIER's reaction from α-Trifluoro-methylketones 1 . The reaction of 2 with anilines and naphthylamines gives in good yields 2-trifluoromethylquinolines 4 and benzoquinolines 5 .