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.     

Erweiterte Spiegelungsgruppen metrischer Vektorräume

The extended reflection groups of a metric vector space (V,f) are introduced and defined by a system of generators and a set of defining relations. It can be proved that they are isomorphic to certain subgroups of the orthogonal groups. The main result of the underlying paper is that these groups can be characterized by a few properties among which we mention the validity of the transitivity theorem and the property of — intersecting . Finally, we obtain a characterization of the (full) groups O^*(V,f) in the case dim V1.

---

---

Herrn Professor Dr. Reinhold Baer zum 75. Geburtstag gewidmet     

Tertiary phosphine abstraction from a platinum(II) coordination complex with SeCN: Crystal and molecular structures of SePTA and [SePTA-Me]I · CH3OH

Reacting [PtCl(PTA)₃]Cl(PTA = 1,3,5-triaza-7-phosphatricyclo[3.3.1.1^3,7]decane) with KSeCN in aqueous or MeOH medium results in the abstraction of the PTA ligands to yield SePTA. The reaction also proceeds quantitatively by direct reaction of PTA and KSeCN in water or methanol. The methylated PTA ligand, [PTA-Me]I (1-methyl-1-azonia-3,5-diaza-7-phosphatricyclo[3.3.1.1^3,7]decane iodide), reacts accordingly with KSeCN, albeit significantly slower. The crystal structure of SePTA, 1, and [SePTA-Me]I · CH₃OH, 2, revealed PSe bond distances of 2.0991(19) and 2.100(2) Å, respectively. The first order phosphorous selenium coupling constants, ¹J_P-Se (D₂O), of 722 and 788 Hz for SePTA and [SePTA-Me]I, respectively, indicates the latter is significantly less electron rich.     

Small-angle static light scattering of concentrated silica suspensions during in situ destabilization

The aggregation of concentrated aqueous silica suspensions is characterized by means of static light scattering. We use an in situ destabilization mechanism based on the enzyme-catalyzed hydrolysis of urea. This method enables us to continuously and homogeneously change the interparticle potential from repulsive to attractive without disturbing the aggregation process. Moreover, our electrostatically stabilized suspensions can be destabilized by two different methods. In the first method, the pH is shifted toward the isoelectric point of the particles ( Delta pH method), thereby leading to a decrease of their surface charge. In the second method, the ionic strength is continuously increased at constant pH ( Delta I method), leading to a compression of the electrical double layer around the charged particles. A laboratory-built flat-cell light-scattering instrument is used, which allows fast data acquisition and an adjustment of the sample cell thickness. To circumvent multiple scattering effects, we use a very small sample thickness ( approximately 13 microm). In addition, the refractive index difference between the aqueous phase and the particles is reduced by adding sucrose to the liquid phase of our suspensions. We are able to characterize the structural changes at the very early stages of the destabilization process, where no significant effects are yet detected in macroscopic rheological measurements. While during the Delta pH destabilization, the scattering curve shows significant changes only after some characteristic delay time, it changes continuously during the Delta I destabilization. The latter is attributed to the formation of a weak pre-gel structure in the suspensions, as a shallow secondary minimum appears in the interparticle potential. Data are evaluated by using a HMSA square-well structure factor model. Results are in good agreement with those predicted from DLVO theory.     

13 C 183W-Kopplungen als sonde für metall—carbin-, —carbenund—alkyl-bindungen

Carbon-13 NMR data are reported for trimethyltin derivatives containing ER_n groups where E  C, Si, Ge, Sn, N, O and S including a series of cyclic amines with ring sizes from three to seven. Coupling constant values for the homologous series of fourth group derivatives give goood correlations with the electronegativity of E. The observation of the two-bond, ¦ ²J(¹¹⁹SnE¹³C) ¦ couplings only in the derivatives containing bulky R groups is rationalized by a bimolecular exchange of ER_n groups in the concentrated solutions studied.     

Capillary electrophoretic detection in apolipoprotein E genotyping

We describe the application of capillary electrophoresis to detect DNA fragments, obtained after amplifying a part of the apolipoprotein E (apoE) gene with polymerase chain reaction (PCR). Compared to conventional agarose slab gel electrophoresis (AGE), CE appears the method of choice with regard to resolution and sensitivity, to detect DNA fragments in the range of 20-100 base pairs. Especially discrimination between apoE2/E2 and apoE2/E3 genotypes is more reliable with CE than with AGE, this being of great clinical value in the diagnosis of familiary dysbetalipoproteinemia.     

Electron distribution on an intramolecular hydrogen bond: A semiempirical AM1 study

Dipole moments of seven molecules were studied by AM1, each containing an intramolecular hydrogen bond between a hydroxyl group and a carbonyl or nitro group as hydrogen acceptors. The hydrogen bond causes two electron shifts: from H to O within the hydroxyl group and from C to O within the carbonyl group. The latter is accompanied by withdrawal of electrons from even more distant atoms. If the total electron density change is expressed as a vector, its direction is close to the direction of the O-H bond. This electron redistribution is in agreement with the previous, somewhat, puzzling experimental results. However, it differs from the commonly accepted picture according to which electron density changes on the hydrogen acceptor moiety are less important than those on the O-H bond.Dedicated to Professor Viktor Gutmann on the occasion of his 70th birthday.