Über die Hydrierung von Aminalen

The catalytic hydrogenation of aminals The catalytic hydrogenation of aminals, the bis-N-analogs of acetals, was investigated. 3-(γ-Aminopropyl)-piperidines are formed by the hydrogenolytic splitting of the C–N-bond of decahydro-1, 8-naphthyridines. The reaction is stereospecifically influenced by the catalyst used. Non cyclic aminals are hydrogenated in the same manner. The mass and NMR. Spectra of 3-(γ-aminopropyl)-piperidines are discussed.     

Über die Stereoselektivität der 9,9′-Spirobifluoren-kronenäther gegenüber α-Aminoalkoholen

Stereoselectivity of 9,9′-Spirobifluorene Crown Ethers towards α-Amino Alcohols Crown ethers I-VI were tested by partition experiments for their stereoselectivity towards α-amino alcohols 1–10. The stereoselectivity depends in a regular way on both the absolute and relative configuration of the crown ether and α-aminoalcohol. Comments are made on some high stereoselectivities.     

Über die optische Reinheit und die Chiralität der enantiomeren α-2H1-Benzylamine

The optical purity and the absolute configuration of (–)-α-²H₁-benzylamine have been determined by NMR. analysis of a mixture of optically pure diastereoisomeric derivatives.     

Über die Stereospezifität der α-Alkylierung von β-Hydroxycarbonsäureestern. Vorläufige Mitteilung

About the Stereospecific α-Alkylation of β-Hydroxyesters It was found, that dianions derived from β-hydroxyesters with lithium diisopropylamide (LDA) at ?50 to ?20° were alkylated stereospecifically (Scheme 1). The stereospecificity was 95–98%, the threo-compound (threo -2, -3 and -4) being the main product. This was proved for threo -2 and -3 by preparing the β-lactones 7 and 8 , respectively, which were pyrolyzed to trans-1, 4-hexadiene (9) and trans-1-phenyl-2-butene (10) , respectively (Scheme 2). Moreover, the acid threo -6 from threo -3 was converted by dimethylformamide-dimethylacetal to cis-1-phenyl-2-butene (11) (s. footnote 6). The alkylation of α-monosubstituted β-hydroxyesters also turned out to be stereospecific. Reduction of 16 and 18 with actively fermenting yeast furnished (+) -17 and (+) -2. respectively (Scheme 4), which were each mixtures of the (2R, 3S)- and the (2S, 3S)-isomers. Alkylation of (+) -17 with allyl bromide yielded after chromatography (2S, 3S) -19 and of (+) -2 with methyl iodide (2R, 3S) -19 , the oxidation of which finally gave (S)-(?) -20 and (R)-(+) -20 , respectively.     

Über die säurekatalysierte Umlagerung von β-Jonon-5,6-epoxid

β-Ionone-5,6-epoxide ( 1 ) undergoes acid-catalyzed ring contraction and enlargement, concurrently, by [1, 2]-alkyl shifts, to give the isomeric cyclopentane derivative 6 and the cycloheptafurane derivative 7 . Spectroscopic and chemical evidence for the structures of 6 and 7 is presented.     

Über die Autoxydation eines α-Aminoketon-Derivates und ihre Beeinflussung durch Metall-Ionen

It is shown that during the autoxidation of a dihydropyrazine, formed by intramolecular cyclisation of the α-acylaminoketone R? CH(COR′)? NH? CO? CH(R)? NH₂ (R′ = (CH₃)₂CHCH₂–, R = CH₃CH₂–), evolution of H₂O₂ is strongly catalysed by Mn diphosphate complexes.     

Isochinoline. 1. Mitteilung. Über die Umlagerung von α, α-Dialkylhomophtalimiden zu Derivaten des 1-Chlor-3, 4-dialkyl-isochinolins

On reinvestigation of the reaction of wet phosphorus oxychloride with α,α-dimethylhomophthalimide, 1-chloro-3-chloromethyl-4-methyl-isoquinoline and 1-chloro-4-chloromethyl-3-methyl-isoquinoline were isolated as the main products (aside from some substances resulting from a redox disproportionation). The production of these two substances can be rationalized by assuming a mechanism in which the rearrangement product is a protonated derivative of 3,4-dimethylene-3, 4-dihydroisoquinoline. With α, α-diethyl-homophthalimide the only isolated product was a derivative of 1-chloro-3, 4-diethyl-isoquinoline, with a chlorine atom in β-position of one of the ethyl groups, while with α-methyl-α-benzyl-homophthalimide the isolated product was 1,3-dichloro-4-methyl-isoquinoline, i.e. elimination had taken place instead of rearrangement. Also these results are in agreement with the proposed mechanism.     

Über einen neuartigen synthetischen Zugang zu β,γ-ungesättigten α-Aminocarbonsäuren

A New Synthetic Route to β,α-Unsaturated α-Amino Acids A versatile new synthetic pathway for the preparation of βγ-unsaturated α-amino acids ( 1 ) is presented. Cu(I)-catalyzed addition of ethyl isocyanoacetate ( 2 ) to α-chloro carbonyl compounds ( 3 ) gives 5-chloroalkyl-2-oxazolin-4-carboxylates ( 4 ) in high yields. A reductive elimination on 4 by means of zinc yields the N-formyl derivatives of βγ-unsaturated α-amino carboxylates ( 5 ), which on acid hydrolysis lead to the free amino acids 1 . The five different βγ-dehydro-α-amono acids 1b-1f have been prepared by this method.     

Über die Reaktion von 2,2-Dimethylpropylidinphosphan mit Molybdänpentachlorid; die Kristallstruktur von [Mo2Cl6(α,α′-Dipyridyl)3]

Reaction of 2,2-Dimethylpropylidynephosphine with Molybdenum Pentachloride; Crystal Structure of [Mo₂Cl₆(α,α′-dipyridyl)₃] 2,2-Dimethylpropylidynephosphine and molybdenum pentachloride dissolved in POCl₃ react with oxydation of the phosphorus and reduction of the molybdenum atom to give the alkyne complex [Mo₂Cl₄(μ-Cl)₂(μ-H₉C₄? C?C? C₄H₉)(OPCl₃)₂]. Addition of α,α′-dipyridyl or of methyltriphenylphosphonium chloride in dichloromethane results in a displacement of the ligands POCl₃ and H₉C₄? C?C? C₄H₉ from this complex and in the formation of [Mo₂Cl₆(dipy)₃] or [(H₅C₆? )₃P? CH₃]₃[Mo₂Cl₉]. Besides the latter compound small amounts of [(H₅C₆? )₃P? CH₃]₂[MoCl₆] can be isolated from the reaction mixture. [Mo₂Cl₆(dipy)₃] which has already been prepared by other methods crystallizes in the monoclinic space group P2₁/c with {a = 1612; b = 148; c = 1296 pm; γ 109.3°; Z = 4} at 20°C. As shown by a crystal structure determination the complex is built up from [MoCl₂(dipy)₂]⁺ cations and [MoCl₄(dipy)]^? anions. The molybdenum atoms are both octahedrally surrounded. With average values of 238 and 243 pm the Mo? Cl bond distances in the cation, where a cis-arrangement of the chlorine atoms is observed, and in the anion differ significantly from each other. [Mo₂Cl₆(dipy)₃] which has already been prepared by other methods crystallizes in the monoclinic space group P2₁/c with {a = 1612; b = 148; c = 1296 pm; γ = 109.3°; Z = 4} at 20°C. As shown by a crystal structure determination the complex is built up from [MoCl₂(dipy)₂]⁺ cations and [MoCl₄(dipy)]^? anions. The molybdenum atoms are both octahedrally surrounded. With average values of 238 and 243 pm the Mo? Cl bond distances in the cation, where a cis-arrangement of the chlorine atoms is observed, and in the anion differ significantly from each other.     

Über die Darstellung und die Eigenschaften von σ-Organylwolframpentachloriden

Tungsten hexachloride reacts with dimethyl zinc or diphenyl zinc forming green methyl or phenyl tungsten pentachloride. However, tungsten hexachloride is reduced to tungsten tetrachloride on addition of zinc dialkyls with longer alkyl groups. Furthermore, alkyl tungsten pentachlorides can be prepared from tungsten hexachloride and tin tetraalkyls or boron trialkyls.     

Über die 1,2-Verschiebung von Carbonestergruppen bei der Benzilsäureumlagerung von α,β-Dioxobuttersäure-estern. 25. Mitteilung über Reduktone und Tricarbonylverbindungen [1]

In the benzilic acid type rearrangement of t-butyl α,β-dioxobutyrate (VII) the intact t-butoxycarbonyl group is shifted to the β-carbonyl carbon atom.     

Über die Oxo‐cyclotetraphosphane (PBut)4O1–4

Contributions to the Chemistry of Phosphorus. 243 On the Oxocyclotetraphosphanes (PBu^t)₄O_1–4 Under suitable conditions, the reaction of tetra‐tert‐butylcyclotetraphosphane, (PBu^t)₄, with dry atmospheric oxygen gives rise to the corresponding monoxide (PBu^t)₄O ( 1 ) which has been isolated by column chromatography. The reaction with hydrogen peroxide furnishes a mixture of oxocyclotetraphosphanes (PBu^t)₄O_1–4 consisting of two constitutionally isomeric dioxides (PBu^t)₄O₂ ( 2 a , 2 b ), the trioxide (PBu^t)₄O₃ ( 3 ), and the tetraoxide (PBu^t)₄O₄ ( 4 ), in addition to 1 . According to the ³¹P NMR parameters the oxygen atoms are exclusively exocyclically bonded to the phosphorus four‐membered ring. Which of the P atoms are present as λ⁵‐phosphorus follows from the different low‐field shifts of the individual P nuclei compared with the starting compound. Accordingly, 1 is 1,2,3,4‐Tetra‐tert‐butyl‐1‐oxocyclotetraphosphane, 2 a and 2 b are 1,2,3,4‐Tetra‐tert‐butyl‐1,2‐dioxo‐ and ‐1,3‐dioxocyclotetraphosphane, respectively, 3 is 1,2,3,4‐Tetra‐tert‐butyl‐1,2,3‐trioxocyclotetraphosphane, and 4 is 1,2,3,4‐Tetra‐tert‐butyl‐1,2,3,4‐tetraoxocyclotetraphosphane. When the oxidation reaction proceeds a fission of the P₄ ring takes place.     

Über die Reaktion von tertiären Vinylcarbinolen mit Isopropenyläther Eine neue Methode zur Herstellung von γ, δ-ungesättigten Ketonen

A novel acid-catalysed reaction of isopropenyl ether with tertiary vinyl carbinols giving γ, δ-unsaturated ketones in high yields is described. Methylheptenone, geranylacetone, farnesylacetone and analogous ketones were prepared by this convenient and efficient new method, which involves a Claisen-rearrangement step.     

Über die Reaktion von tertiären Vinylcarbinolen mit Vinyläthern Eine neue Methode Zur Herstellung von γ,δ-ungesättigten Aldehyden

A novel acid catalysed reaction of vinyl ethers with tertiary vinyl carbinols giving γ, δ-unsaturated aliphatic and alicyclic aldehydes in high yields is described. This new procedure for the utilization of the Claisen rearrangement reaction provides a convenient and efficient route to such aldehydes.     

Über die Verbindung Sr7Mn4O15 und Beziehungen zur Struktur von Sr2MnO4 und α-SrMnO3

On the Compound Sr₇Mn₄O₁₅ and Structure Relations to Sr₂MnO₄ and α-SrMnO₃ The “compound” hitherto described as a α modification of Sr₂MnO₄ is shown to consist of a mixture of SrO and the new monoclinic compound Sr₇Mn₄O₁₅ crystallizing in the space group P 2₁/c, a = 681.78(6), b = 962.24(8), c = 1038.0(1) pm, β = 91.886(7)°, Z = 2. Up to 0.3 mm long black crystals were grown from prereacted Sr₇Mn₄O₁₅, SrO, and SrCl₂ at 1350°C in a sealed platinum tube under argon. Its structure is related to α-SrMnO₃. It contains layers of cornershared double octahedra [O_2/2OMnO₃MnO₂O_1/2]^7? parallel to (100). Above 100 K the magnetism of Sr₇Mn₄O₁₅ follows the Curie Weiss law with Θ ～ -426 K and a moment μ_eff = 3.62 μ_B corresponding Mn⁴⁺.