Der Mechanismus der Umlagerung substituierter Aminoacrylderivate

Thioacetic acid and dithioacetic acid react with alkynederivatives of the type (CH₃)₂N? C?C? CO? R ( 1 ) in the same way as other carboxylic acids: The addition to dimethylaminopropinal ( 1a ) at low temperatures yields, after rearrangement of the very instable primary adducts, Z-3-acetoxy-N,N-dimethyl-thioacrylamide ( Z-16 ) and Z-3-thioacetoxy-N,N-dimethylthioacrylamide ( Z-17 ) respectively. The structure of the two compounds can be proved by spectroscopic evidence of 16 and 18 , the latter being formed by elimination of thioketene from 17 . According to the distribution of S-atoms in 16 and 17 , two reaction pathways including 4-membered rings can be ruled out. Thus the rearrangement of 3-acyloxy-N,N-dimethyl-acrylamides most probably proceeds by a mechanism including a dipolar six-membered intermediate. This mechanism cannot be valid for the rearrangement of the adducts 2 of hydrohalogen acids, alcohols and amines to the alkyne-derivatives 1 . The acid-catalysed reaction of 3-chloro-3-dimethylamino-propenal ( 2 , X?Cl), labelled at position 1 with ¹³C, yields 3-chloro-N,N-dimethyl-acrylamide ( 3 , X?Cl), containing the label exclusively at position 3 . This result supports a mechanism including an immonium-oxetene 21 (X?Cl) as intermediate. - The experiments are in accord with kinetic investigations.     

Präparative und spektroskopische Untersuchungen an Dialkylthalliumverbindungen mit Tl-N-Bindung

Inhaltsübersicht. Es wird über die Darstellung von primären und sekundären Dialkylthalliumamiden, R₂Tl—NR′R″, berichtet und die neuen Verbindungen durch analytische und spektroskopische (H-NMR, IR, MS) Methoden charakterisiert. Die verschiedenen Reaktionsmöglichkeiten der Tl—N-Bindung werden erläutert. Preparation and Spectroscopic Investigations on Dialkylthallium Compounds with Tl—N Bond Abstract. The preparation of primary and secondary dialkylthallium amides, R₂Tl—NR′R″, is reported and the new compounds are characterized by analytical and spectroscopic (¹H-n.m.r., i.r., m.s.) methods. Various possibilities of reactions of the Tl—N bond are discussed.     

Präparative chromatographische Enantiomerentrennung von synthetisch nützlichen cyclischen Acetalen

Preparative Chromatographic Resolution of Synthetically Useful Cyclic Acetals Racemic cyclic acetals derived from aldehydes and glycine, glycolic acid, thioglycolic acid, formylacetic acid, and acetoacetic acid (oxazolidinones 4 – 13 , dioxolanones 14 , 15 , oxathiolanone 16 , dioxinones 17 – 23 ) are resolved by preparative high-pressure liquid chromatography on silica gel coated with the polymer from N-acryloylphenylalanine ethyl ester (Chiraspher®). The separation factors α range from1,1 to 2,4. Use of a Prepbar®-chromatography system allows injection of several grams at a time. The enantiomeric acetals thus obtained are fully characterized. First application to amino-acid synthesis are mentioned.     

Untersuchungen an Stichstoff–Jod-Verbindungen. VI. Präparative und infrarotspektroskopische Untersuchungen an N-Jodmethylaminen

Studies on nitrogen iodine compounds. VI. Preparation and infrared studies on N-iodomethylamines N-diiodomethylamine and N-iododimethylamine can both be prepared under special conditions only. N-diiodomethylamine forms solid adducts with methylamine, trimethylamine and pyridine. The diodomethylamines show IR spectra similar to those shown by (NI₃ · NH₃)_n and demonstrating an analogous polymeric structure; iododimethylamine according to its spectrum is thought to be a monomeric substance.     

Untersuchungen an Stickstoff-Jod-Verbindungen. IX. Präparative und infrarotspektroskopische Untersuchungen an Jod-Komplexen von N-Jodmethylaminen

Studies of Nitrogen Iodine Compounds. IX. Preparation and I. R. Investigations of Iodine Complexes of N-Iodine Methylamines [CH₃NI₂]₂ · I₂, [(CH₃)₂NI]₂ · I₂ and (CH₃)₂NI · I₂, have been prepared. The IR-spectra have been obtained in the region 33–4000 cm^?1. The spectra can be coordinated on the ground of a molecule model with 5 atoms Z₂XYW of the symmetry C_s and are compared to that of CH₃NI₂. The structures of the compounds are proposed to be monomolecular.     

Präparative Darstellung von μ-Disauerstoff-bis-kobalt(II)-Chelaten

Binuclear cobalt chelates with O₂ as bridging ligand have been prepared, using ethylenediamine, triethylenetetramine, tetraethylenepentamine and tris-(2-aminoethyl)-amine as chelating agents and SCN^? and ClO₄^? as anions. They form well characterized crystals which give off molecular oxygen spontaneously in acid solution and, except in the case of the cobalt tetra-ethylenepentamine chelate, reveal the general composition [(Z)Co · μ(O₂, OH) · Co(Z)]X₃, where Z represents the polydentate complexing agents and X the anion. In the presence of ammonia different complexes are produced, in which NH₃ occupies one coordination site of each cobalt, replacing the hydroxo bridge.     

Präparative Reindarstellung und Charakterisierung von trimerem,tetramerem und pentamerem Selenoformaldehyd

Preparation and Characterization of Pure Trimeric, Tetrameric, and Pentameric Selenoformaldehyde The possibilities for the preparation of three oligomer forms of selenoformaldehyde are described. Their separation from polymethylene selenide and oily byproducts is possible by aid of recrystallization, sublimation and a complexation-decomplexation treatment with AgNO₃. So for the first time s-pentaselenecane could be isolated. The properties of the selenoformaldehydes are described. Their complexes with AgNO₃ serve for additional characterization.