Synthesis of chloro aldehydes of the heterocyclic series

A method was developed for the preparation of 4-chloro-5-formylimidazolones, Δ⁴-thiazolinones, and 4-chloro-5-formyluracils by reaction of 4-azolidones or barbituric acids with dimethylformamide and phosphorus oxychloride.     

The Instability of Permanganate in orthophosphoric acid

Solutions of potassium permanganate in concentrated phosphoric acid (above 50%) are found to be unstable. The oxidation state of manganese is reduced from (VII) to (III) and oxygen is evolved during this process. The extent of decomposition of permanganate is found to be dependent on the concentration of the acid.     

Stickoxid in Gasgemischen, z. B. in Dieselauspuffgasen

Ohne Zusammenfassung     

Synthesis and applications of C2-symmetric guanidine bases

The preparation of the tetracyclic C₂-symmetric guanidinium salts 5 and 11-13 is reported together with their application to enantioselective transformations.     

On the synthesis and chiroptical properties of the tri- and tetragalloylquinic acids

Summary A synthesis of the potential pharmaceutical agents 3,4,5-trigalloylquinic acid and 1,3,4,5-tetragalloylquinic acid is described. It involves three steps starting from commercially available quinic acid and provides overall yields of about 15%. The acylation of benzyl or 4-nitrobenzyl quinate with tribenzylgalloyl chloride is the key step. It leads selectively to the triacyl product in the case of benzyl quinate and can be either stopped at the triacyl stage or driven to the tetraacyl derivative in the case of the 4-nitrobenzyl quinate. From the chiroptical properties of the two compounds their stereochemistry was derived by means of the benzoate rule.

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Zu Synthese und chiroptischen Eigenschaften der Tri- und Tetragalloylchinasäuren

Zusammenfassung Eine Synthese von 3,4,5-Trigalloylchinasäure und 1,3,4,5-Tetragalloylchinasäure. die potentielle Pharmaka darstellen, wird beschrieben. Sie umfaßt drei Stufen, welche ausgehend von kommerziell erhältlicher Chinasäure Gesamtausbeuten um 15% ergeben. Die entscheidende Stufe dabei ist die Acylierung von Benzyl- oder 4-Nitrobenzylchinat mit Tribenzylgalloylchlorid. Sie führt im Falle des Benzylchinats selektiv zum Triacylprodukt und kann im Fall des 4-Nitrobenzylchinats entweder auf der Stufe des Triacylderivates abgebrochen oder bis zum Tetraacylprodukt durchgezogen werden. Aus den chiroptischen Eigenschaften der beiden Verbindungen wurde ihre Stereochemie abgeleitet.

     

Detection and semiquantitative determination of bismuth(III) in water on immobilized and plasticized polyurethane foams with some chromogenic reagents

Polyurethane foams immobilizing 1,2-di-(2-fluorophenyl)-3-mercaptoformazan (F(2)H(2)Dz) and dithizone (H(2)Dz) have been used for the detection of bismuth(III) in water via batch, dynamic and pulsated column modes of extraction. The detection limits of bismuth(III) with the F(2)H(2)Dz- and H(2)Dz-immobilized foams were found to be 0.01 and 0.02 mug ml(-1) respectively. Lower concentrations (相似文献   

Radiochemistry of germanium

Since the publication ofRadiochemistry of Germanium (NAS-NS-3043) in 1961, there have been significant developments on the subject. During the period from 1970 to 1980, the diagnostic utilization of the⁶⁸Ge⁶⁸Ga generator system in nuclear medicine stimulated research in the field. In addition, over the past 30 years there have been many advances in the analytical chemistry of germanium (Ge), owing to the rapid increase in application of Ge in the electronics industry and, most recently, as an important component in infrared spectrometers.This fatest review has been completely rewritten. A literature search has been completed through December of 1990. Literature for selected topics has been surveyed through September 1993. The first section contains general information about germanium and its radioisotopes, and relevant nuclear data in tabulated form. In the second section, a general review of the inorganic and analytical chemistry of Ge is presented. Following these two introductory sections, subsequent sections deal with the production and preparation of germanium radioisotopes, separation and determination of Ge, of particular interest to the radiochemist, and selected procedures for its determination in or separation from various media. The section on separation chemistry has been greatly expanded.The review includes sections on hot-atom chemistry and the chemical behavior of carrier-free⁶⁸Ge. A section entitled Applied Radiochemistry of Germanium deals specifically with⁶⁸Ge⁶⁸Ga generator systems, the role of⁷¹Ge in the detection of solar netrinos, and the preparation of⁶⁸Ge positron sources for studying dislocations in metallic lattices and calibration of Positron Emission Tomography (PET) cameras.Two other noteworthy points follow. Throughout the text, the oxidation state of a metal ion having only one stable state, such as germanium, is not explicitly indicated. Therefore, Ge typically represents Ge⁴⁺. Other ions such as arsenic and tin, however, are indicated with their appropriate oxidation states. The term carrier-free applies to radioactive preparations to which no isotopic carrier (stable isotopes) is intentionally added.     

Synthesis and study of structure of 5-formyl-substituted 2,3,4,5-tetrahydro-1H-1, 5-benzodiazepin-2-ones

A series of 5-formyl derivatives was synthesized by formylation of 2,3,4,5-tetrahydro-1H-1,5-benzodiazepin-2-ones with a mixture of formic acid and acetic anhydride. The structure of their rotation isomers was studied by PMR spectroscopy.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 7, pp. 957–961, July, 1988.     

Evidence for facile atropisomerism and simple (non-nucleophilic) biradical-forming cycloaromatization within kedarcidin chromophore aglycon

The kinetics and thermodynamics of atropisomerism within the protected kedarcidin chromophore aglycon 8, as well as a series of ansa-bridged synthetic intermediates leading to 8, were determined by 1H NMR spectroscopy. The data show that the ratio of atropisomeric forms of chloropyridine-bridged ansa intermediates is subject to wide variation with seemingly subtle structural variation. The vinyl bromide 4, for example, in the first X-ray structure determination of a kedarcidin ansa-bridged system, was found to exist as a single atropisomer in the solid state, but a nearly equal mixture (K = 0.70) of isomers in solution (t1/2 for isomer interconversion approximately 0.2 s at 20 degrees C). The aglycon 8, a 2.2:1 mixture of atropisomers, was found to undergo direct unimolecular biradical-forming cycloaromatization at ambient temperature in a mixture of 1,4-cyclohexadiene-benzene, without nucleophilic activation. The product 9 was formed as a single atropisomer (k = 2 x 10-4 s-1, t1/2 = 58 min, 81% yield), suggesting that the rate of atropisomerism within 8 is rapid with respect to cycloaromatization. The rate of cycloaromatization of 8 was found to be highly solvent-dependent, being more rapid in the presence of a good hydrogen-atom donor, consistent with the earlier model studies of Hirama et al. that showed that certain nine-membered cyclic (Z)-enediynes may equilibrate with their biradical cycloaromatization products. Incubation of 8 with beta-mercaptoethanol, under conditions mimicking experiments leading to DNA cleavage with kedarcidin, showed no evidence for nucleophilic activation. The product of direct cycloaromatization (9) was isolated instead. The evidence suggests that kedarcidin, like the enediyne agent C-1027, is capable of spontaneous thermal biradical formation without prior chemical activation.