Reaktivität und Selektivität bei der Oxidation von Styrolderivaten. V. Untersuchungen zur Oxidation von α-substituierten Styrolen

Reactivity and selectivity in the oxidation of styrene dderivatives. V. Studies on the oxidation of α-substituited styrenes. The liquid phase oxidation of -phenyl-( 1a ), α-trimethylsilyloxy ( 1b ), α-cyclopropyl-( 1c , α-trifluoromethyl-( 1d ) styrene, and styrene ( 1e ) with oxygen in chlorobenzene and cumene solution in the temperature range 55-125 °C was investigated. The product yields were determined gaschromatographically. The epoxide selectivity increases up to 90 °C with increasing temperature. The epoxides of 1a and 1c rearrange at higher temperatures, therefore their yield decreases. The relative chain propagation constants (k_pCC) were determined by competitive oxidations of cumene.     

Reaktivität und Selektivität bei der Oxidation von Styrolderivaten,II. Untersuchungen zur Oxidation von p-substituierten α-Methylstyrolen

Reactivity and Selectivity in the Oxidation of Styrene Derivatives, II. Studies on the Oxidation of p-Substituted α-Methylstyrenes The liquid phase oxidation of p-substituted (Br-, Cl-, t-Bu-, MeO-, CF₃-) α-methylstyrenes and of α,p-dimethoxystyrene with pure oxygen was investigated in chlorobenzene solution and in presence of cumene and of cumene hydroperoxide in the temperature range 65–125°C. The product yields were determined gaschromatographically. The differences of the activation energies of the epoxide formation and the parallel reactions amount to 19–48 kJ/mol. The epoxide selectivity increases with increasing temperature and concentration of olefine. The relative chain propagation constants k_p (CC) were determined by competitive oxidation with cumene. The k_p(CC) values of p-substituted α-methylstyrenes can be correlated by the Hammett equation with both σ and σ⁺ substituent constants.     

Untersuchungen zur Oxidation von α-substituierten Styrolen. I. Reaktivität und Produktbildung bei der Oxidation von Styrol-Derivaten

Studies on the Oxidation of α-Substituted Styrenes. I. Reactivity and Formation of Reaction Products During the Oxidation of Styrene Derivatives The liquid phase oxidation of α-tert. -butyl-, α-bromo-, α-chloro-, and α-methyl styrene with pure oxygen was investigated in a closed apparatus in chlorobenzene solution and in presence of cumene and of cumene hydroperoxide in the temperature range 35–125°C. The product yields were determined gaschromatographically. The differences of the activation energies of the epoxide formation and the parallel reactions were calculated. They amount to 27–38 kJ/mol. The epoxide selectivity increases with increasing temperature and decreases with increasing concentration of cumene. Relative chain propagation constants related to the tertiary CH-bond of cumene were determined from cooxidation experiments.     

4-Anilino-5,7-dinitrobenzofurazan – Untersuchungen zur Struktur und Reaktivität

4-Anilino-5,7-dinitrobenzofurazan – Studies on Structure and Reactivity 4-Anilino-5,7-dinitrobenzofurazan 3 reacts with gaseous ammonia at room temperature under elimination of aniline leading to 4 . Compound 3 may also be transformed into the isolable salt 6 by treatment with aqueous KHCO₃, whereas 4 reacts with KHCO₃ furnishing potassium 5, 7-dinitrobenzofurazan-4-olat 5 . As shown by X-ray analysis and CNDO/2 calculations of 3 , the case with which the nucleophilic substitutions proceed may be explained by the assumption of an azomethine structure in 4 and 6 .     

Vinyloge Acylverbindungen. XX. Reaktivität und Toxizität arylsubstituierter β-Chlorvinylketone, β-Chlorvinylaldehyde und β-Chlorvinylmethyleniminiumsalze

Vinylogous Acyl Compounds. XX. Reactivity and Toxicity of Aryl-substituted β-Chlorovinyl Ketones, β-Chlorovinyl Aldehydes, and β-Chlorovinyl Methyleniminium Salts Based on kinetic measurements, the nucleophilic replaceability of the chlorine in aromatic β-chlorovinyl ketones ArCO-CH  CH-Cl ( 1 ), isomeric β-chlorovinyl aldehydes OCH CHC(Cl)Ar( 2 ), and corresponding β-chlorovinyl methyleniminium salts Me₂N^⊕;CH CHC(Cl)Ar X^⊖ ( 3 ) is compared and related to toxicological findings. The chemical reactivity of these important synthetic building blocks increases in the order 2 < 1 < 3 , the acute toxicity (24 h LD₅₀ i. p. in the mouse) shows the graduation 2 < 3 < 1 . Compounds of type 1 prove to be relatively toxic (LD₅₀ 24–42 mg/kg) and display a marked necrotic action after percutaneous absorption, whereas the aldehydes 2 have not only a minor acute toxicity (LD₅₀ 158–298 mg/kg) but also a somewhat less marked skin damaging activity. In addition, the LD₅₀ values of selected β-chlorovinyl carbonyl compounds are compared with those of corresponding halogen-free compounds as well as of vinylogous carbonamidium salts ArCO CHCH N^⊕R₃X^⊖. The latter, which can be used as synthetic equivalents of 1 , differ in both the reduced acute toxicity and missing skin damaging properties.     

Untersuchungen zur Spin-Trapping-Kinetik in Systemen von Radikalen unterschiedlicher Reaktivität. Die Photolyse von α-Phenylbenzoin in Gegenwart von Benzyliden-tert.-butylamin-N-oxid

Investigations on Spin-Trapping Kineties in Radical Systems with Different Reactivity. Photolyses of α-Phenylbenzoine in the Presence of Benzylideneter. -butylamine N-oxide As a model system to study the spin-trapping kinetics of systems forming two radicals of different reactivity α-phenylbenzoine (PhB) was chosen. The photolysis of PhB forms benzoyl (B·) and diphenylketylradikals (K·), respectively, which can be trapped by benzylidene-tert-butyl-amine N-oxide (PBN), as a spin trap. The rate constants of radical addition to PBN and their reactions with the spin adducts were determined by means of flash photolysis and kinetic calculations of the PBN concentration dependence. For B· and K· addtion rate constants to PBN of k₁ = 8,1 × 10⁵ M⁻¹s⁻¹, and k₂ = 5,8 · 10⁴ M⁻¹s⁻¹, respectively, were found. The rate constants for the reactions of B· and K· with the spin adducts are in the order of 10⁹…10¹⁰ M⁻¹s⁻¹.     

Cyclisierungsreaktionen β,γ-ungesättigter Kohlensäurederivate. XI [1] Untersuchungen zur Stereochemie der Cyclofunktionalisierung β,γ-ungesättigter Carbamidsäureester

Cyclization Reactions of β,γ-Unsaturated Derivatives of Carbonic Acid. XI. Investigation of Stereochemistry of the Cyclofunctionalization of β,γ-Unsaturated Carbamic Acid Esters N, N-Disubstituted β,γ-unsaturated urethanes 1 have been cyclized to 3,5-disubstituted oxazolidine-2-ones 3 by aromatic sulfenyl chlorides 2 . The stereochemistry of the products and the cyclofunctionalization reaction were investigated.     

Partialsynthesen von Cardenoliden und Cardenolid-Analogen. I. α,β- und β,γ-ungesättigte Lactonring-methylierte Cardenolide

Partial Syntheses of Cardenolides and Cardenolide Analogues. I. α,β- and β,γ-Unsaturated Lactone Ring-Methylated Cardenolides Base-catalyzed methylation of digitoxigenin 1a with methyl iodide and sodium hydride in DMF leads to the α,β-unsaturated cardenolides 2–5 and, after rearrangement of the CC-double bond, to the β,γ-unsaturated cardenolides 6 and 7 . Opening of the lactone ring results in the formation of 8 . Allylic oxidation of 4b affords the 14,21-epoxide 10 . Only the 22-methyl derivative 4a and its 3-O-tridigitoxoside 4d show strong biological effectivity, whereas methylation at 21R- or 21S-position results in considerable loss in activity.     

α-Substituierte Phosphonate. 43. Synthese und Reaktivität von 1,2,3,4-Tetrahydroisochinolin-1-phosphonaten

α-Substituted Phosphonates. 43. Synthesis and Reactivity of 1,2,3,4-Tetrahydroisochinolin-1-phosphonates N-Alkyl- and N-arylsubstituted 1,2,3,4-tetrahydroisochinolin-1-phosphonates 1 have been synthesized from the corresponding 3,4-dihydroisochinoliniumbromides 7 and triethyl-phosphite. The N-unsubstituted 1,2,3,4-tetrahydroisochinolin-1-phosphonate 10 is available starting from the 1,2,3,4-tetrahydroisochinolin-1-phosphonic acid by esterification with triethylformate and splitting off the formyl group of the primarily formed N-formyl derivative 14 . – N-Quarternated tetrahydroisochinolines 19 and the 1-phosphorylated derivatives 17 , respectively react with triethyl-phosphite in an unexpected way by dealkylation and not by splitting off the isochinolinring. – By Horner-synthesis with 1 the 1-aralkylidene-isochinolines 23 are available in moderate yields.     

Selektivität bei der Fetthydrierung,früher und heute I

Selectivity of Hydrogenation in Former Days and at Present A review is presented on the present knowledge on catalytic hydrogenation of fatty oils with special reference to selectivity of catalyst systems during hydrogenation. From the viewpoint of development of fat hydrogenation, heterogeneous catalytic hydrogenation is extensively discussed, and, subsequently, homogeneous catalytic hydrogenation, a rather new branch of science, is briefly described. The entire review is limited to those aspects that are significant for the production of fats with increased melting point.     

Cyclisierungsreaktionen β, γ-ungesättigter Kohlensäurederivate. IV [1]. Synthese von N-substituierten Thiazolidin-2-onen und 2-Alkoxy-2-thiazolinen aus β,γ-ungesättigten Thiocarbamidsäureestern

Cyclization Reactions of β,γ-Unsaturated Derivatives of Carbonic Acid. IV. Synthesis of N-Substituted Thiazolidine-2-ones and 2-Alkoxy-2-thiazolines from β,γ-Unsaturated Thiocarbamic Acid Esters The reaction between N-substituted β,γ-unsaturated thiourethans and dry hydrogen chloride or bromine occurs in methylene chloride at room temperature. The thiourethans 1 a–4 a react with hydrogen chloride to give mixtures of corresponding 2-alkoxy-2-thiazolines 6–9 and the thiazolidine-2-one 11 a . A useful synthetic route to N-substituted thiazolidine-2-ones 11 is demonstrated by the reaction of N,N-disubstituted β,γ-unsaturated thiourethans with hydrogen chloride and bromine. The i.r. and H-n.m.r.-data of the compounds are described.