Zur Synthese 3,5,6-substituierters-Triazin-2,4-dione

The reaction of N-(2-pyridyl)-carbaminates (3), 1-phenyl-3-(2-pyridyl)-urea (5 a) or alkyl and aryl substituted pyridopyrimidinediones (2) synthesized from 2-amino-pyridine with arylisocyanates (4 a, b) yields 3-aryl substituted pyrido-[1,2-a]-s-triazine-2,4-diones (1). 2-Aminopyridine and azamalonic derivatives (ethoxycarbonyl isocyanate, ethyl iminodicarboxylate) react to give the 3-unsubstituted triazine system (1 c). The isolation of monocyclic triazinediones obtained from the reaction of N-phenylbenzamidine (9) with aryl isocyanate (4 a) or ethoxycarbonyl isocyanate failed because of hydrolytic ring opening. The mechanism of the reaction of 3-substituted pyrido-pyrimidinediones (2) and phenyl isocyanate (4 a) is discussed.     

Quantum field theoretical methods in chemically bonded systems II

Summary Many-body perturbation theory is derived for chemical bonds. Paired quasiparticles represent the bonds. Products of the paired quasiparticles define a model Bardeen-Cooper-Schrieffer function. The pairing force is added as a model interaction to the self-consistent problem. The starting model is based on valency and adiabatic symmetry correlation. Symmetries are enforced by the model Hamiltonian. Perturbative corrections are expressed as ordinary Feynman diagrams. The number of diagrams needed is the same as for particle-hole theory.This work was supported in part by the U.S. Department of the Navy, Space and Naval Warfare Systems Command under Contract N00039-89-C-0001, and in part by NATO Research Grant 1861. It was presented, in part, at the A.C. Wahl Memorial Session, Molecular Spectroscopy Symposium, Columbus, Ohio, 1984; and Midwest Theoretical Chemistry Conference, Milwaukee, Wisconsin, 1985.     

Über das Anwachsen der Lösungen linearer Differentialgleichungen mit rationalen Koeffizienten in Winkelräumen

Let z=∞ be the only irregular singular point of the linear differential equation $$(D)w^{(n)} + P_{n - 1} (z)w^{(n - 1)} + \cdots + P_o (z)w = 0$$ with rational coefficients p_j(z). If w is a multivalent and irregular solution of (D), we define the index I(τr,W), τ ∈ (0,1), of a branch W of w in the plane cut along a half ray. If r→∞, I(τr,W) possesses a finite number of aymptotic directions being exactly the asymptotic directions of the points z with maximal possible modulus of W(z). It follows that each branch W is of mean type σ(W)=|d|/λ in each sector containing an asymptotic direction of I. The possible values of the order of growth λ=λ(W)<∞ and the constant d are given by the PUISEUX-diagram of (D).     

Conformations of the ten-membered ring in 5,10-secosteroids I. X-ray and NMR. Analysis of (E)-3 β-hydroxy-5,10-seco-1(10)-cholesten-5-one esters

X-ray structure determination of the p-bromobenzoate 2b of one of the (E/Z)-isomeric 3β-hydroxy-5,10-seco-1(10)-cholesten-5-ones confirmed the (E)-configuration proposed previously and showed the cyclodecenone ring to adopt an extended crown conformation of type A ₁ (Fig. 9). Analysis of the ¹H- and ¹³C-NMR. spectra of acetate 2a revealed that in solution the ten-membered ring of this steroid exists in at least two distinct forms, the predominant (about 85%) corresponding to the solid-state conformation of 2b (= A ₁), and the minor most likely to B ₂ (Fig. 9). From NMR. data the energy difference between the two species and the relevant activation energy were estimated. A number of conformational force field calculations using a simplified partial structural model was performed; but the computed energy differences between the various possible conformations do not reproduce the effective situation, neither in solution nor in the crystal lattice, indicating that additional effects such as the transannular interaction of the double bond with the carbonyl group may strongly influence the thermodynamic stability of the system. The conformations deduced were used to rationalize the stereochemical course of different chemical reactions of 2a .     

Simple instrument for titrimetry without visual indicators. gasometric titrations: Cerimetry,chlorometry, nitrate,nitrite, hydroxide and carbonate determination

It was shown in previous papers, that many titrimetric problems can be solved by observing the pressure change of a closed system above the solution titrated at the equivalence point. This principle was made the basis of a gasometric titration method in which the end-point is found graphically. The titrant is added to the sample solution in measured increments at fixed intervals of time and the corresponding gas pressure or volume of the system is recorded and then plotted against the volume of added titrant. Half a dozen readings are sufficient to establish the end-point of a titration, which is found at the intersection of two straight lines. This graphical method was applied to cerimetry and chlorometry, as well as to some other analytical reactions (determination of nitrite, nitrate, hydroxide and carbonate) already described in previous papers on the gas pressure end-point technique. The results are comparable in precision and accuracy to the values obtained by the conventional visual end-point titrations. A gasometric titration takes about 10 minutes. The presence of other substances in the sample capable of reacting with the titrant does not necessarily cause interference.     

Numerical solution of a partial differential equation system describing chemical kinetics and diffusion in a cell with the aid of compartmentalization

To build a kinetic model of a cell with diffusion one has to solve a coupled nonlinear partial differential equation system consisting of several hundred equations. (Several hundred chemical components undergoing several hundred reactions.) To solve this formidable mathematical problem the division of the model cell into compartments (most biochemical reactions take place in a certain part of the cell) was suggested.¹ Solving the differential equation system in one compartment, the results can be used as input at other compartments until mutually consistent solutions are achieved. To test this suggestion 10 coupled chemical reactions with diffusion were investigated in a model that contains three compartments. The results in the case of pure diffusion are in excellent agreement with and without compartmentalization. After this the full problem was treated by compartmentalization using for the solution of the differential equation system a discretization of the concentrations as functions of space and time and the Newton–Raphson iterative procedure. The results obtained give reasonable space and time dependence for the concentrations of all 10 components.     

Synthesis of 1,2-Diazol-4-sulfonamides, 1,2,4- and 1,2,5-Oxadiazol-3-sulfonamides, 1,2,3-Triazol-4-sulfonamides, and Pyrimidine-5-sulfonamides starting from Cyanomethanesulfonyl Chloride

Summary. Cyanomethanesulfonyl chloride was reacted with amines yielding cyanomethanesulfonamides which could be transformed into alkoxymethylidene and aminomethylidene derivatives. The reaction of alkoxymethylidene derivatives with phenylhydrazine resulted in the formation of 5-aminopyrazol-4-sulfonamides, whereas from cyanomethanesulfonamides via the N-hydroxyamidine derivatives and their reaction with esters 1,2,4-oxadiazol-3-methanesulfonamides became accessible. Nitrosation of cyanomethanesulfonamides yielded 2-hydroxyimino derivatives which were then transformed into 2-hydroxyimino N-hydroxyamidine derivatives, and finally cyclized into 4-amino-1,2,5-oxadiazol-3-sulfonamides. On the other hand diazotation of cyanomethanesulfonamides gave the 2-arylhydrazono derivatives, which after transformation into N-hydroxyamidine derivatives gave by reaction with POCl₃ 5-amino-1,2,3-triazol-4-sulfonamides. Finally, the reaction between cyanomethanesulfonamides and formamidinium acetate opened an easy access to 4-aminopyrimidine-5-sulfonamides, which could be transformed by trialkyl orthoformiates into substituted pyrimidino[4,5-e][1,2,4]thiadiazine derivatives. All intermediates as well as transformation products of the heterocyclic systems were isolated and well characterized. Mechanisms were discussed, and the stereochemistry, when necessary and possible, was elucidated.     

Ethylene tetramerization: a new route to produce 1-octene in exceptionally high selectivities

Linear alpha-olefins, such as 1-hexene and 1-octene, are important comonomers in the production of linear low-density polyethylene (LLDPE). The conventional method of producing 1-hexene and 1-octene is by oligomerization of ethylene, which yields a wide spectrum of linear alpha-olefins (LAOs). While there exists several processes for producing 1-hexene via ethylene trimerization, a similar route for the selective production of 1-octene has so far been elusive. We now, for the first time, report an unprecedented ethylene tetramerization reaction that produces 1-octene in selectivities exceeding 70%, using an aluminoxane-activated chromium/((R2)2P)2NR1 catalyst system.     

Investigation of potential-sensitive fluorescent dyes for application in nitrate sensitive polymer membranes

The applicability of various potential-sensitive dyes (PSD) for optical sensing of anions is reported. Specifically, nitrate-responsive polymer membranes have been developed which are composed of a plasticized polymer, an anion exchange catalyst, and a fluorescent dye. On exposure to nitrate, the fluorescence intensity of such membranes increases, while the wavelengths of the excitation and emission maxima remain virtually unchanged. The membranes typically are 2–4 μm thick and exhibit highest sensitivity to nitrate in the 2 to 200 mgl^–1 range. Signal changes on exposure to 100 mmol/l nitrate can be as high as +300%. The detection limit is 0.2 mgl^–1. The cationic PSD octadecyl acridine organe was tested in combination with a tin-organic and an indium-organic anion carrier rather than with tridodecylmethylammonium chloride, but both carriers were found to display no improved selectivity. Received: 2 December 1995 / Revised: 28 March 1996 / Accepted: 5 April 1996     

Syntheses of fluorescent dyes. IX. New 4-hydroxycoumarins, 4-hydroxy-2-quinolones, 2H,5H-Pyrano[3,2-c]benzopyran-2,5-diones and 2H,5H-Pyrano[3,2-c]quinoline-2,5-diones

7-Substituted 4-hydroxycoumarins (2a-e) and 4-hydroxy-2-quinolones (2f-i) have been synthesized from the appropriate phenols or anilines and were converted to the enamines 3 using triethoxymethane and aniline. Condensation of 3 with nitriles 4a-h gave substituted 2H,5H-pyrano[3,2-c]benzopyran-2,5-diones (5a-r) or 2H,5H-pyrano[3,2-c]quinoline-2,5-diones (5s-x) , which exhibit both spontaneous and stimulated fluorescence with maxima between 418 and 549 nm. The marked influence of an electron withdrawing 3-substituent in 5 is demonstrated by the fluorescence spectra of 7a,b (synthesized from 2d,e and ethyl 3-oxobutyrate), whose maxima are sharply shifted to the blue as compared with compounds 21-r.