Pyryliumverbindungen. XXI. Struktur und Tautomerie von Pseudobasen unsymmetrisch substituierter 2,4,6-Triarylpyryliumsalze

Pyrylium Compounds. XXI. Structure and Tautomerism of Pseudobases of Unsymmetrically Substituted 2,4,6-Triarylpyrylium Salts Hydrolytic ring opening of unsymmetrically substituted 2,4,6-triarylpyrylium salts 11 results in a mixture of two tautomeric pseudobases, the penten-1,5-diones 13 and 14 . In crystalline state as a rule one of these tautomers markedly predominates, whereas in solution a rapid equilibrium establishment occurs which can be followed by ¹H-n.m.r. and u.v. spectroscopy (equilibrium ratio nearly 1:1). The ¹H-n.m.r. spectroscopic structural assignment of the two isomeric forms was supported by u.v. spectroscopic studies using 1:1 mixtures of the chromophoric partial systems ArCOCHCHPh and ArCOMe or the pseudobases 10 of symmetrically substituted 2,4,6-triarylpyrylium salts 9 as reference systems. From the mass spectra of the pseudobases 10 and 13 / 14 follows that – if hydrolysis of 11 is performed in media containing H₂¹⁸O – mass spectrometric isotopic analysis of the resulting ¹⁸O-labelled pseudobases allows no information to be made about the regioselectivity of the ring opening. – Novel starting pyrylium salts of type 9 and 11 are characterized by u.v./vis data and by transformation into the corresponding pyridine derivatives.     

Pyryliumverbindungen,XXV. Quantenchemische Berechnungen zur Valenzisomerisierung von 2-Amino-2H-pyran und -thiopyran

Pyrylium Compounds. XXV. Quantum Chemical Calculations Concerning the Valence Isomerization of 2-Amino-2H-pyran and -thiopyran The equilibrium 2-amino-2H-pyran 6 ⇌ 5-amino-2,4-dien-1-one 7 was investigated using the semi-empirical MINDO/3 and MNDO methods. In accordance with experimental findings for the substituted derivatives 1/2a–d , the introduction of a methyl group into the position 3 of 6 or the exchange of oxygen by sulfur shifts the equilibrium towards the cyclic structures 8 and 10 , respectively. Polar solvents, the influence of which was estimated applying the reaction field approach as well as the solvaton theory, and entropy effects are calculated to favour the ring-open valence isomer 7 . These results also correspond to experimental results.     

Untersuchungen zur regioselektiven Halogenierung von 4-Amino-2-iodmethyl-6-methyl-pyrimidinen

Studies on the Regioselective Halogenation of 4-Amino-2-iodomethyl-6-methylpyrimidines In the presence of oxidants, 4-amino-2-iodomethyl-6-methylpyrimidines 2 undergo regioselective reactions in the positions 2 and/or 5. Thus, the reaction of 2a with hydrogen peroxide proceeds under dealkylation and iodination to give 4-amino-5-iodo-6-methylpyrimidine 7 . Depending on reaction temperature and molar ratios the reaction of 2a with bromine or chlorine leads to the corresponding 4-amino-5-halogeno-2-halogenomethyl-6-methyl-pyrimidines 2c, 9a and 9d . The 5-substituted pyrimidines 2b, c afford the 2-bromo (or chloro) methyl derivatives 9b, c .     

1H-NMR-, 13C-NMR- und IR-Untersuchungen zur Tautomerie von 15N-markiertem 3-Methyl-1-phenyl-Δ2-pyrazolin-5-on

¹H-N. M. R., ¹³C N. M. R., and I. R.-Investigations Concerning Tautomerism of ¹⁵N-Labeled 3-Methyl-1-phenyl-Δ²-pyrazolin-5-one The behaviour of the ¹⁵N-mono and dilabeled compound in dependence on temperature and solvent polarity is described. Chemical shifts, ⁿJ(¹⁵N ¹H), and ⁿJ(¹⁵N ¹³C) coupling constants (n = 1 – 3) have been determined. In the cases of 2, 2, 2-trifluoroethanole and hexafluoroisopropanole the Δ⁴-pyrazolin-3-one is stabilized and detected by ³J(¹⁵N 2 H 4) = 3 Hz, ¹J(¹³C 3 ¹⁵N 2) = 11, 0 Hz and δ(¹³C 5). In HMPT the 5-hydroxypyrazole form predominates and is characterized by ³J(¹⁵N 1 H 4) = 5, 1 Hz and δ (¹³C 5). Coupling constants ³J(¹⁵N 2 H 4) and J(¹³C 3 ¹⁵N 2) could not be observed in this solvent. In accordance with ¹H- and ¹³C-n. m. r.-parameters i. r. measurements in dependence on temperature lead to the conclusion that in DMSO and THF for instance all three tautomers are present and variation of temperature does not change the equilibrium between the tautomers. A good relationship between the content of the CH₂, OH and NH forms and the Donor Numbers (DN) and Acceptor Numbers (AN) by Gutmann has been found.     

Prostaglandine und Prostaglandinvorstufen. Untersuchungen zur Synthese von 8-Methylprostansäurederivaten

Prostaglandins and Prostaglandin Intermediates. Synthetic Approach to 8-Methyl Prostanoic Acid Derivatives Starting from the chiral key-product 1 the 8-methyl prostanoic acid derivative 13 was prepared within 10 steps. Construction of the α-side chain involves DIBAH-reduction of the lacton moiety of 1 followed by Wittig-olefination with a C₅-ylide. C₁-Homologation of the oxo group of 1 via cyanhydrin synthesis and Wittig-olefination with a C₇-ylide are important steps to form the ß-side chain of compound 13 .     

Untersuchungen zur Copolymerisation von Äthylen und Vinylacetat unter Hochdruck

The influence of the vinylacetate content and of the reaction conditions on the conversion in the ethylene vinylacetate-copolymerization was investigated in the ranges of 2 to 9 wt.-% vinylacetate, 1100 to 1900 atm, 200 to 240°C and 60 to 90 wt.-ppm initiator. From these measurements the activation energies and the frequency factors of the main reaction steps— initiation, chain growth and chain termination—were calculated. Furthermore the dependency of the structure and of some important technical properties was determined from the analysis of the obtained polymers as well as from infrared spectroscopic data and by gel-permeation chromatography.     

Untersuchungen zur Sulfochlorierung von Paraffinen. III. 1H- und 13C-NMR-Spektren aliphatischer und cycloaliphatischer Mono- und Disulfochloride

Studies on the Sulphochlorination of Paraffins. III. ¹H- and ¹³C-N.M.R. Spectra of Aliphatic and Cycloaliphatic Mono- and Disulphonylchlorides Isomeric monosulphonylchlorides of propane, butane, and heptane as well as disulphonylchlorides of propane, butane, and pentane are measured ¹H- and ¹³C-n.m.r.-spectroscopically. Including several other aliphatic and cycloaliphatic sulphonylchlorides, the use of n.m.r. spectroscopy to identification and estimation of the composition of mono- and disulphonylchloride mixtures is discussed.     

Synthese substituierter 2-Nitrophenylhydrazone von 2-Oxodicarbonsäureestern und Untersuchung ihres Tautomerie- und Absorptionsverhaltens

Synthesis of Substituted 2-Nitrophenylhydrazones of 2-Oxodicarboxylic Acid Esters and Investigation of Their Tautomerism and Absorption Behaviour 32 Substituted 2-nitrophenylhydrazones of diethyl oxalacetate, 2-oxoglutaric acid and its 1-mono- and 1,5-dialkyl esters, resp., have been synthesized from substituted 2-nitrophenylhydrazines and 4,6-dinitro-1,3-dihydrazinobenzene and the carbonyl compounds named above. ¹H-n.m.r. spectra prove all products to have the constitution of hydrazones and not that of azo compounds or enhydrazines and also allow the assignation of the E- and Z-configuration, resp., to the hydrazone diastereomers. The absorption behaviour of all hydrazones is discussed with comparison of the different substitution patterns. Unexpectedly, the 4,6-dinitro-1,3-bishydrazones 27 – 32 show very high lg ϵ_max values (at about 4.8) due to their crossed two chromophoric systems.     

Untersuchungen zur Freisetzungsgeschwindigkeit von Salicylsäure aus Salbenschichten, 2. Die Abhängigkeit der Freisetzungsgeschwindigkeit von rheologischen Parametern und der Löslichkeit in Kohlenwasserstoffgemischen und anderen Salbengrundlagen

Studies on the Rate of Liberation of Salicylic Acid from Ointment Layers, 2. Dependence of Rate of Liberation on Rheological Parameters and Solubility in Hydrocarbon Mixtures and Other Ointment Bases Influences of solubility, HLB-value and selected rheological parameters on the liberation of salicylic acid from ointment layers were investigated. Simple and multifactorial correlation calculations show that the solubility of salicylic acid in the ointment layer is the most importent factor, whereas the rheological parameters have a detectable effect, only when ointments of similar chemical composition are compared. Moreover, the HLB-value has no significant effect and the interface tension of ointment/water is only of minor significance.     

Protonierung und Solvatation schwacher organischer Basen. III. UV- und 1H-NMR-spektroskopische Untersuchungen zur Basizität von 1,3-Diketonen

Protonation and Solvation of Weak Organic Bases. III. U.V. and ¹H-N.M.R. Spectroscopic Investigations of the Basicity of 1,3-Diketones By ¹H-n.m.r. spectroscopy it is possible to determine separately the basicity parameters (H₀)_1/2 or pK and the solvation paramters m, ϕ or m^* for the keto and the enol form of acetylacetone. By u.v. spectroscopy only brutto parameters of the equilibrium mixture for acetyl- and benzoylacetone as for dibenzoylmethane are available.