Search

r-5-(α-Halogenobenzyl)-3, t-4-diaryl-c-4-hydroxy-oxazolidin-2-ones as Ring Tautomers of α-(N-Arylaminocarbonyloxy)-β-halogeno-dihydrochalcones The reaction of chalcone halogenohydrins (1–3) with arylisocyanates does not stop at the stage of the α-arylaminocarbonyloxy-β-halogeno-dihydrochalcones (7), but the cyclic urethanes 4–6 are formed. Compound 7h was synthesized independently. The structure and stereochemistry of 4–6 and 7h were determined by 13C n.m.r. spectroscopy.

Reactions of 1,3-Dipoles with Heterocycles, 8. — Synthesis of 1,8a-Dihydro[1,2,4]triazolo[4,3-a]pyridines and Benzologues The C,N double bond of pyridine, quinoline and isoquinoline as heterodipolarophile react with diarylnitrilimines 2, generated in situ by dehydrohalogenation of N-phenylbenzhydrazonoyl chlorides 1, in a cycloaddition with complete regioselectivity. A facile route to hitherto unreported 1,3-diaryl-1,8a-dihydro[1,2,4]triazolo[4,3-a]pyridines 3, 1,3-diaryl-3,3a-dihydro[1,2,4]triazolo[4,3-a]quinolines 4, and 1,3-diaryl-1,10b-dihydro[1,2,4]triazolo[3,4-a]isoquinolines 5 has been developed. In a similar way, cycloadditions are carried out with C-ethoxy-carbonyl- and C-acetyl-N-phenylnitrilimines. The ring cleavage of 3 in acidic medium yields the corresponding [(arylhydrazono)methyl]pyridinium chlorides 7. The conversion of the open-chain products back to 3 has been carried out in pyridine containing triethylamine. Anodic oxidation of 3–5 in aprotic medium affords the [1,2,4]triazolohetarenium perchlorates 9–11. The yields in such reactions are either similar or better than with chemical oxidants. The thermally initiated cycloreversion of 3 and 5 is discussed, judging from the facts that the thermolysis afford 2:1 cycloadducts.

The first synthesis ofthreo chalcone bromohydrins was realized by reaction oftrans chalcone epoxides with SnBr4 in molar ratios from 1:1 to 2:1. The compounds were obtained in high yields and isomeric purity. Their configuration was determined asthreo by different methods based on13C-NMR shifts of C-α and C-β atoms.

The electron-transfer-sensitized photolysis of substituted phenyl-(trimethylsilyl)methyl ethers was studied. N-Methylquinolinium perchlorate, p-tolyltropylium perchlorate and 9,10-dicyanoanthracene were used as electron acceptors. The main reaction of the stabilization of the radical cation of the ether (the intermediate formed by single electron transfer to the singlet-excited acceptor) is CO bond cleavage. With 9,10-dicyano-anthracene as acceptor 100% phenol is formed. The competing CSi bond cleavage is a minor reaction in the case of the quinolinium salt. This leads to addition of the ether fragment and the acceptor. The photoexcited tropylium salt does not induce any reaction of the added ether. The quantum efficiencies of ether cleavage are relatively high and depend on the donor capacity of the substituent in the phenyl ring. This is explained by competition between back electron transfer and bond cleavage in the radical pair formed. Electron paramagnetic resonance (EPR) was used to detect the intermediate radicals and flash photolysis to detect the anion radicals.

Die spektrometrischen Untersuchungen in Losungen belegen eindeutig die dominie-rende Rolle der Dithionform bei den Dithiomalonamiden, fur die Enthiol-thion-Form gibt es nur geringfugige, nicht eindeutige Hinweise bei einigen IR-Festkorperspektren. Spectroscopical Investigations on N,N′-Disubstituted Dithiomalonamides and their Co(II)-Complexes The Co(II)-complexes of N,N′-disubstituted dithiomalonamides have been synthesized and characterized. Comparative uv/vis-, ir-, epr-, x-ray-, and n.m.r.-spectral studies of this complexes and of the dithiomalonamides suggest that their Co(II)-compounds are S4-coordinated square planar inner complexes (CoL2). The orbital splitting parameters Δ of these complexes have been calculated in the order of less than 20000 cm−1. For compounds CoL2 by this way the following spectrochemical series of the ligands results: dmma < d clmma < dnma < d clpma < dpma. All dithiomalonamides investigated in this work exist nearly complete in the dithion-form.

Hammett Relationships between 1H-NMR and 31P-NMR Chemical Shifts, Respectively, and Substituent Constants in ω-Diphenylphosphinyl and ω-Diphenylthiophosphinyl trans-Styrenes A well linear correlation between the chemical shifts of the ethylenic protons HB and the 31P nuclei, respectively, and the Hammett constants σp of substituents R in 4-position for diphenylphosphinyl trans-styrenes 1 and the analogous diphenylthiophosphinyl trans-styrenes 2 has been found. A similar relationship for the proton HA has been observed in the case of 1 only, but the substituent-induced shifts are not so sensitive. Donor substituents R in 1 and 2 effect an increase in the shielding of HB and a deshielding of the P atom being connected with shifts of the i. r. PO absorption bands in 1 in the direction of lower wavenumbers. A mesomeric interaction between R and PY substituents (Y = O, S) is concluded to produce polymethin-like π-electron density distribution.

N,N-Dialkylamides of 2-Hydroxy-2-phenyl-cyclopropan-1-carboxylic Acid – Photochemical Synthesis and Determination of the Structure Irradiation of N,N-dialkylamides of β-benzoylpropionic acid 2a, b in ether by n,π*-excitation leads to the corresponding amides of the hitherto unknown 2-hydroxy-2-phenyl-cyclo-propancarboxylic acid 3a, b, 4a, b. The photocyclization yields diastereomeric mixtures E:Z = 2.5–3:1. The determination of the relative configurations is based on the different tendency of dimerization of the E and Z diastereomers.

Zusammenfassung Die Kinetik der anodischen Pyrazolbilding wurde mit Hilfe der rotierenden Pt-Scheibenelektrode in Acetonitril in Anwesenheit von Pyridin fur eine Reihe von 1,3,5-Triaryl-Δ 2 -pyrazolinen untersucht. Der geschwindigkeitsbestimmende Schritt dieser nach einem e.c.e.-Prozess pseudo-1. Ordnung ablaufenden Reaktion ist die Deprotonierung der Pyrazolin-Radikalkationen. Eine lineare Freie-Enthalpie-Beziehung zwischen dem Logarithmus der Geschwindigkeitskonstanten k 1 und den anodischen Halbstufenpotentialen zeigt, dass dieser Teilschritt um so schneller ablauft, je mehr die Bildung der Radikalkationen unter dem Einfluss von Substituenten zu positiven Potentialen verschoben wird. Dieser Substituenteneffekt auf die Aciditat der reagierenden C-H-Bindungen wird auch anhand der chemischen Verschiebungen und der Kopplungskonstanten im 1 H-n.m.r.-Spektrum der Pyrazoline sichtbar.

Reactions by Participating of Ylide-Intermediates. III. On Preparation and Structural Elucidation of Spiro-condensed Tetrahydroindolizines N-(Fluroen-9-yl)-pyridinium- and -isoquinolinium ylides (5) to (8) react with electrondeficit olefinic dipolarophiles under mild conditiones to give satisfactory to good yields of the corresponding spirocondensated tetrahydroindolizines (10) to (13). The structure and configuration of all isolated products were elucidated by spectroscopical methods, especially by 1 D- and 2 D 1H-n.m.r. The 1.3-dipolar cycloaddition produced regiospecific cycloadducts. From the observed regiospecifity of unsymmetrically substituted olefines (9) can be concluded that the cycloaddition is HOMO(1.3-dipole) — LUMO(dipolarophile) controlled. The olefines (9) add stereospecifically under retention of their configuration via exo as well as endo transition states. The nitrosubstituted ylides (6) and (8) produced always mixtures of diastereomeric cycloadducts (11) and (13).

Substituent Effects in 13C- N. M. R. Spectra of Diastereomeric Chalcone Dihalogenides. V. Synthesis, Stereochemistry and Spectroscopy of Chalcone Fluorohydrines Chalcone fluorohydrins 1 and diastereomeric pairs of chalcone chlorohydrins 2 as standards are investigated in the i.r., 1H, 19F, and 13C n m. r. spectroscopy field. The substituent dependence of the spectral parameters is discussed. The assignment of conformation and configuration on the basis of vicinal 1H1H, 1H19F, and 1H13C coupling constants is determined.

β-D-Glucopyranosylthioharnstoff, von uns als Modellsubstanz fur die MAILLARD-Reaktion ausgewahlt, bietet auf Grund seines mehrfunktionellen Charakters zugleich die Moglichkeit, Heterocyclen zu synthetisieren. Werden unter diesem Blickwinkel β-D-Glucopyranosylthioharnstoff oder Tetra-O-acetyl-(β-D-glucopyranosyl)-thioharnstoff mit Cyclisierungsreagenzien wie Acetylendicarbonsaureethylester oder substituierten Phenacylbromiden zur Reaktion gebracht, erhalt man N-Gluoosylaminothiazole bzw. -aminothiazine. Das N-Glucosyl-aminothiazin konnte so erstmals synthetisiert werden. Das aus β-D-Glucopyranosylthioharnstoff dargestellte N-(β-D-Glucopyranosyl)-N′-(carboxymethyl)-guanidin wird in einer intramolekularen Reaktion zu einem in zwei tautomeren Formen vorliegenden Imidazolon cyclisiert. Die 1H-Kernresonanzspektren und die massenspektrometrische Fragmentierung der Syntheseprodukte belegen deren Struktur.

1H-N. M. R., 13CN. 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(15N1H), and nJ(15N13C) 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(15N2H4) = 3 Hz, 1J(13C315N2) = 11, 0 Hz and δ(13C5). In HMPT the 5-hydroxypyrazole form predominates and is characterized by 3J(15N1H4) = 5, 1 Hz and δ (13C5). Coupling constants 3J(15N2H4) and J(13C315N2) 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.

31P-NMR Investigation of N-Aryl-substituted Iminotriphenylphosphoranes: Hammett Relationship between 31P Chemical Shift and Substituent Constants The 31P chemical shifts of p- and m-substituted N-arylimino-triphenylphosphoranes reflect the electronic influence of the substituents and can be correlated by a Hammett relationship. This new correlation was used for the estimation of σ- resp. σ-values for p-(CH3)2N-, p-C6H5CO- and p-C6H5N N-groups as well as for β-naphthyl- and pyridyl(4)-rings. The applicability of a similar Hammett equation for the o-substituted compounds is not possible.

Chalcone Aziridines. III. Reaction of trans-Chalcone Aziridines with Isocyanates, Isothiocyanates and HSCN The reaction of 2-aryl-3-aroyl-aziridines 1 with phenyl isocyanate or mustard oils leads to N-phenylcarbamoyl derivatives 2a–2q and 2-amino-thiazolines 6 a, h, n, r, respectively. From 2 m and NaI the imidazolin-2-one 3 was obtained. By treatment of 2 with HSCN the regiosomeres 2(3)-ureido-3(2)-rhodano-1. 3-diaryl-propan-1-ones 4 a, h, m and 5 f were formed.

Protected Aminooxazolines of Arabinose and Ribose The reaction of D-arabinose or D-ribose with cyanamide afforded 2-amino-1,2-oxazolines 1 which were treated with dihydropyran or ethylvinylether. In the presence of PTS the 3′,5′-di-THP- or 3′,5′-di-O-ethoxyethyl-D-arabino-(ribo)-furo-[1′,2′:4,5]-2-oxazolines 2 and 3 could be isolated as useful intermediates for the preparation of nucleosides. When the 2-aminooxazolines are treated with benzyloxycarbonylchloride or its p-substituted derivatives the N-3 atom of the oxazoline ring is preferentially substituted. Under these conditions the exocyclic amino function is always replaced and 2-oxo-3-benzyloxycarbonylderivatives 4 are obtained; only traces of the corresponding 2-aminoderivatives 5 are formed. Treatment of 4 with acetic anhydride, benzoylchloride, and benzoylcyanide, respectively, results in the 3′-, 5′-di-O-acyl derivatives 6. Mild hydrolysis of the benzyloxycarbonyl group with trifluoroacetic acid yields the 3′,5′-di-O-acyl-D-arabino-(ribo)-furo-[1′,2′:4,5]-2-oxooxazolidines as further intermediates for the synthesis of nucleosides.

1H-N.M.R. Investigation of Pyrido [1.2-a]1.3.5-triazines: Through Bond and Through Space Effects of Ringintegrated Carbonyl, Thiocarbonyl, and Iminocarbonyl Groups From the 1H-n.m.r. spectra of pyrido[1.2-a]1.3.5-triazines 1a–i the characteristic data δ(H6), δ(H8), and J(H6, H7) are submitted. The ring-integrated carbonyl groups in the position 2 (CX) show a deshielding electronic through bond effect on the protons H6 and H8 in the order of CNPh < CO < CS. On the other hand, the relative through space effect of these groups is in the order CO < CNPh < CS; this relation was determined by their deshielding influence in the position 4 (CY) on the peristanding proton H6. Finally the synthesis and the dissoziation behaviour of the new pyridotriazines 1d and 1h are described.

N.M.R. Spectroscopical Investigations on the Conformational Behaviour of Some 2′ - and 3′-Halogen-substituted Pyrimidine Nucleosides A series of 2′- and 3′-halogenated pyrimidine nucleosides has been synthesized and investigated by 1H, 13C and 19F n.m.r. spectroscopy. The 1H and 13C chemical shifts for the positions 2′ and 3′ depend linearly but oppositely on the substituent electronegativities XR. The conformational equilibrium N ⇌ S of the nucleosides in solution is determined. An approximately linear correlation between the prefered gauche-gauche interaction of the exocyclic CH2OH groups and the ribose N conformation has been found.

Electrochemistry of Organic Cations. IV. Investigations on the Cathodic Dimerization of Alkyl Substituted Pyridinium Ions and on the Chemical Behavior of Dimeric Dihydropyridines The cathodic dimerization of a series of 1,2,4,6-tetraalkylpyridinium ions 1 in acetonitrile and in alkaline aqueous medium as well as the chemical behavior of the bis-[1,4-dihydropyridinyl-(4)] derivatives 2 obtained were investigated. In protic solvents 2 isomerizes by transformation of one or two α-methyl groups into methylene groups with simultaneous change of one dihydropyridinyl ring to a tetrahydropyridinyl- (3) or to a piperidinyl ring (4). The reaction with carboxylic anhydrides, phenylisocyanate, phenylisothiocyanate or the phenyldiazonium ion occurs at the exocyclic double bond formed by this isomerization and leads to acylmethylen-, N-phenylcarbamoylmethylen-, N-phenylthiocarbamoylmethylen- or phenylazomethylen-substituted 4.

1H and 13C n.m.r. Spectroscopical Measurements and HMO-π-Calculations to the π-Electronic Structure of p,p′-Disubstituted trans-Stilbenes and Substituted trans-β-Styryl-methyl-Sulfones The 1H and 13C n.m.r. spectra have been measured for a series of donator-acceptor-disubstituted trans-stilbenes 1 and monosubstituted β-styryl-methyl-sulfones 2. The 13C n.m.r.-signals have been identified by comparison with empirical calculated chemical shifts and quantum chemical determined HMO-π-electrons densities. The influence of substitutents to the experimental chemical shifts are discussed in detail. For 1 and 2 exist linear correlations between chemical shifts and HAMMETT values, and π-electron densities, respectively.

Spectroscopical and Dipole Moment Investigations of Halogen Fluoride Addition Products of Chalcones Chalcone halogen fluoride addition products 1–3 are investigated in the i.r. and 1H-n.m.r. spectroscopy field as well as in the substituent dependence of spectral parameters and molecular dipole moment. The assign of configuration and conformation on basis of 1H-n.m.r. spectroscopy and dipole moments are discussed.

Die Reaktionen von N-[Pyridyl-(2)]-thiazolyl-(2)-amin 1 mit Elektrophilen werden im Hinblick auf die relative nucleophile Reaktivitat von Pyridin und Thiazol untersucht. Es wird uber die Bromierung, Nitrierung, Sulfonierung sowie Aminoalkylierung von 1 berichtet. Alle Reaktionen verlaufen selektiv unter Substitution der 5-Position des Thiazolrings. Die NMR-Daten von 1 und seiner Substitutionsprodukte werden mitgeteilt.

Applications of the Nuclear Overhauser Effect. I. Investigations of the Structure of Z/E Isomeric 2,3-Diarylazetidin-3-oles The relative configurations of Z/E-isomeric 2,3-diaryl-azetidin-3-oles are determined by mass spectrometry and 1H-n.m.r.-NOE-measurements. The increase of the C(2)-H line intensity by saturation of the OH-signals demonstrates the Z-position of the 2,3-diaryl groups in the isomers 2a.