Cyclisierungsreaktionen β, γ-ungesättigter Kohlensäurederivate. II. Reaktionen β, γ-ungesättigter Carbamidsäurederivate mit elektrophilen Reagenzien - Synthese von N-substituierten Oxazolidin-2-onen

Cyclization Reactions of β,γ-Unsaturated Derivatives of Carbonic Acid. II. Reactions of β,γ-Unsaturated Carbamic Acid Esters with Electrophilic Reagents — Synthesis of N-Substituted Oxazolidine-2-ones N,N-Disubstituted β,γ-unsaturated urethans have been cyclized to N-substituted oxazolidine-2-ones by dry hydrogen chloride in methylene chloride. The N-substituted urethan 1a reacts with hydrogen chloride to form the urethan 2a and the 2-oxazoline 3 Reaction of 1 with bromine yields the corresponding N-substituted 5-bromomethyl oxazolidine-2-ones 6     

Cyclisierungsreaktionen β,γ-ungesättigter Kohlensäurederivate. IX. Regiochemie der elektrophilen Cyclofunktionalisierung β,γ-ungesättigter Carbamidsäureester mit Brom – Synthese von Oxazolidin-2-onen und Tetrahydro-2H-1,3-oxazin-2-onen

Cyclization Reactions of β,γ-Unsaturated Derivatives of Carbonic Acid. IX. Regiochemistry of Electrophilic Cyclofunctionalization of β,γ-Unsaturated Carbamic Acid Esters with Bromine – Synthesis of Oxazolidine-2-ones and Tetrahydro-2H-1,3-oxazine-2-ones N,N-Disubstituted β,γ-unsaturated urethanes ( 1 ) and bromine react in methylene chloride at room temperature. The crotyl urethanes ( 1a – 1c and 1e ) and bromine give mixtures of corresponding saturated urethanes (dibromine adducts) ( 2a – 2c and 2e ), the oxazolidine-2-ones ( 3a – 3c and 3e ), and the tetrahydro-2H-1,3-oxazine-2-ones ( 4a – 4c and 4e ). The reaction of γ,γ-dimethylallyl urethanes ( 1f – 1h ) with bromine gives similar results. A useful synthetic route to N-substituted tetrahydro-2H-1,3-oxazine-2-ones ( 4l – 4q ) is demonstrated by the reaction of cinnamyl urethanes ( 1l – 1q ) with bromine.     

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.     

Cyclisierungsreaktionen β,γ-ungesättigter Kohlensäurederivate. VII. Synthese eindeutig N-acylierter Thiazolidin-2-one und Oxazolidin-2-one

Cyclization Reactions of β,γ-Unsaturated Derivatives of Carbonic Acid. VII. Synthesis of Unequivocal N-Acylated Thiazolidine-2-ones and Oxazolidine-2-ones A new synthetic route to N-acylated thiazolidine-2-ones and oxazolidine-2-ones is reported: The reaction of carboxylic acid chlorides with 2-alkoxy-2-thiazolines ( 1, 2 ) or -2-oxazolines ( 3 ) yields unequivocal N-acylated thiazolidine-2-ones ( 4–6 ) or oxazolidine-2-ones ( 7 ). Bifunctional acid chlorides, e.g. oxalyl chloride or thiophosgene yield compounds 11 and 12 .     

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.     

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.     

Synthese und Reaktionen von β-Campholenverbindungen

Synthesis and Reactions of β-Campholene Compounds In contrast to the well known α-campholenic ( B ) and fencholenic compounds ( C ) little is known about β-campholenic derivatives ( A ) because of their difficult accessibilitiy. β-Campholenic compounds ( A ) can be obtained: (1) by Baeyer-Villiger oxidation of camphor via lactone 7 and β-dihydrocampholenic lactone ( 5 ); (2) by Beckmann fragmentation of camphor oxime via α-( 2 ) and β-campholenic nitril ( 3 ) and the lactone 5 ; and ( 3 ) by acid catalysed rearrangement of α-campholenic derivatives ( B , 17a , b ). The β-analogous brahmanol ( 14 ) can be synthesized by the reaction of the β-campholenic bromide ( 11 ) with methyl diethyl malonate or by rearrangement of brahmanol.     

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.     

Die Reaktion von α,β-Dihalogen-propionitrilen mit monosubstituierten Hydrazinen - einfache Synthese 1-substituierter 3- bzw. 5-Amino-pyrazole

The Reaction of α,β-Dihalogeno-propionitriles with Monosubstituted Hydrazines — A Simple Synthesis of 1-Substituted 3- or 5-Amino-pyrazoles In methanol hydrazines 3 , and α,β-dihalogeno-propionitriles 1, 2 even at 0°C irreversibly yield 3 · HX, and α-halogenoacrylonitriles 4, 5 (A₁). Fast addition of alkyl- and aralkyl- hydrazines 3 to 4, 5 (C) gives 1-substituted 1-(2′-halogeno-2′-cyan-ethyl)-hydrazines 6 , the addition of arylhydrazines 3 to 4, 5 (D) 1-aryl-2-(2′-halogeno-2′-cyan-ethyl)-hydrazines 8 . In methanol 6 spontaneously cyclise (E) to hydrogen halides 7 · HX of 1-alkyl- and 1-aralkyl-3-amino-pyrazoles, 8 with 2 moles of acids (F) to salts 10 · 2HY of 1-aryl-4-halogeno-5-imino-pyrazolidines, and the free 10 spontaneously (G) to hydrogen halides 9 · HX of 1-aryl-5-amino-pyrazoles. Mechanisms (A₁), (C), (D), (E), (F), and (G) are proved by t.l.c., ¹H-n.m.r., and isolation of intermediates, the structures of 7 resp. 9 , using the significant ¹H-n.m.r.-parameter Δ. Simple general syntheses are described for 3-amino-pyrazoles 7 (R = H, alkyl, aralkyl) or 5-amino-pyrazoles 9 (R = aryl) starting with α,β-dihalogeno-propionitriles 1, 2 , and for α-bromo-acrylonitrile 5 .     

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.