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1.
Enantioselective 1,4-additions of organometallic compounds to conjugated systems in the chiral medium DDB 1 DDB = 1,4-Dimethylamino-2,3-dimethoxybutan (= 2,3-Dimethoxy-N,N,N′,N′-tetramethyl-1,4-butandiamin). The chiral methoxyamine DDB is used as a cosolvent to add achiral Li-, Cu-, and Zn-organic compounds enantioselectively to prochiral β-carbon atoms of α, β-unsaturated aldehydes, ketones, nitro compounds and ketene-thioacetals (Tables 1 and 2). The selectivity generally ranges from 55:45 to 63:27, in one case ( 9b ) an enantiomeric excess of 43% was obtained. 相似文献
2.
G. Mixich 《Helvetica chimica acta》1972,55(3):1031-1038
The renal excretion of AZAPROPAZONE-DIHYDRATE (X) 1 Handelsname: PROLIXAN®. Hersteller: Siegfried AG, Zofingen. by humans was investigated. Following oral administration a new substance was detected in the urine besides X by TLC. Both compounds were separated by preparative layer chromatography and shown to be unchanged X and its hydroxylated metabolite VIII. The structure of VIII was established by chemical and spectroscopic methods (IR., NMR.) and confirmed by synthesis (Scheme 1). 相似文献
3.
Furaneol® 1 Registered trade mark of Firmenich SA. [4-hydroxy-2,5-dimethyl-3(2H)-furanone ( 1 )], a flavour component of pineapple and strawberry, has been prepared by a two-step synthesis starting with readily available 3-hexyne-2,5-diol. By the same method 4-hydroxy-5-methyl-3(2H)-furanone ( 2 ) and 2-ethyl-4-hydroxy-5-methyl-3(2H)-furanone ( 3a ) have been prepared from 2-pentyne-1,4-diol and 3-heptyne-2,5-diol, respectively. 相似文献
4.
The deuterioformylation of (Z)- or (E)-2-butene catalyzed by [DIOP]Pt(SnCl3)-Cl 1 DIOP=2,3-O-isopropylidene-2,3-dihydroxy-1,4-bis(diphenylphosphino)butane. gives predominantly erythro- or threo-1,3-[2H]2-2-methylbutanal respectively. Hence, hydroformylation by this catalytic system must take place with cis-stereochemistry. 相似文献
5.
Technical Procedure for the synthesis of Carotenoids and Related Compounds from 6-Oxo-isophorone 1 Teil 4 dieser Reihe: [1]. . V. Synthesis of Astacene Starting from optically inactive astaxanthin intermediates, the highly oxygenated carotenoid astacene was synthesized in seven steps (55% overall yield from 6-oxo-isophorone). Key features of the new approach are base- and acid-catalyzed rearrangements of acetylenic intermediates such as those described in Schemes 2, 7 and 8. 相似文献
6.
Manfred Weidenbruch Jrg Hockemeyer Karl Peters Hans Georg von Schnering 《无机化学与普通化学杂志》1994,620(7):1163-1169
Silicon Compounds with Strong Intramolecular Steric Interactions. 54 1 Mitteilung 53: K. Peters, E.-M. Peters, H. G. von Schnering, H. Piel, M. Weidenbruch, Z. Kristallogr., im Druck. . Attempted Generation of a Diaminosilylene: Formation of Spirosilanes and of Related Compounds Treatment of the bulky substituted N,N′-bis(2,6-dimethylphenyl)ethylenediamine with n-butyllithium and subsequent cyclization with trichlorosilane or silicon tetrachloride gives the 2-chloro- and 2,2-dichloro-1,3-diaza-2-silacyclopentanes 3 and 4 , respectively. Both compounds can easily be converted into the azido- ( 5 ) and diazidosilanes ( 6 ) and into the trisilane 7 . Chlorine elimination from 4 in the presence of 2,3-dimethylbutadiene leads to the spirosilane 9 containing a nine-membered ring, whose structure was confirmed by X-ray crystallography. Reaction of 4 with lithium, followed by treatment with isopropanol gives beside other products the compound 10 consisting of two diazasilacyclopentane rings linked by a bridging ethylenediamino group. The X-ray structure determination of 10 shows that all six nitrogen atoms have a nearly planar environment. Upon photolysis, the azidosilane 5 provides the disiladispiro compound 12 , presumably via a silanimine intermediate. 相似文献
7.
Dieter Schelz 《Helvetica chimica acta》1978,61(7):2452-2462
On the Synthesis of 1-Aryl- and-1-Alkyl-2, 3-dimethyl-quinoxalinium Perchlorates. 2nd Communication 1 1. Mitt.: [1]. . Synthesis and 1 H-NMR. Spectra of 2, 3-Dimethyl-1-phenyl-6-X-quinoxlinium Perchlorates The synthesis of the title compounds ( 5 ) which have been useful as precursors for a lot of conventional and new-type dyes [2-8] has yet been limited to examples with X?H [2] [3] [11] [15] and with electron-donating [4] [12] or at best slightly electron-accepting [1] [6] substituents X and R. We now describe a method suitable even for compounds 5 with strongly electron-accepting substituents: N-monosubstituted o-phenylendiamines 4 , were condensed with 2, 3-butanedione and perchloric acid in mixed solvents containing an excess of diethyl ether. The products - mostly substituted at position 6 of the quinoxalinium ring - are chracterized by 1H-NMR. spectra, elemental analyses and in most cases by isolation of the corresponding bases 6 . Correlations of chemical shifts with Hammett's σp [18] are given by equations (1)-(5). 相似文献
8.
Mass spectra of ginsenoside-Rg1 deca-acetate 1 Siehe Lit.2. and the related dammaran-type triterpene saponin acetates have been studied and a comment is given on the structure of panaxoside A (=ginsenoside-Rg1) proposed by Elyakov, et al . 相似文献
9.
Yi-Bin Xiang Susanne Drenkard Karl Baumann Deirde Hickey Albert Eschenmoser 《Helvetica chimica acta》1994,77(8):2209-2250
Chemistry of α-Amino Nitriles 1 11. Mitteilung: [1]. . Exploratory Experiments on Thermal Reactions of α-Amino Nitriles The paper extends a previously published report [4] on chemical properties of α-amino nitriles and of members of the C3H4N2 ensemble (Scheme 1) as observed in experiments carried out under non-aqueous conditions. The reactions investigated and the observations made are summarized in some detail in the English footnotes (*) referring to Schemes 1–17 and Fig. 1. 相似文献
10.
Jian Wu Tamaki Nakano Yoshio Okamoto 《Journal of polymer science. Part A, Polymer chemistry》1998,36(12):2013-2019
A novel racemic methacrylate, (2-fluorophenyl)(4-fluorophenyl)(2-pyridyl)-methyl methacrylate1 (2F4F2PyMA), was synthesized and polymerized with chiral complexes of N,N′-diphenylethylenediamine monolithium amide (DPEDA-Li) with (−)-sparteine (Sp), (2S, 3S)-(+)-2,3-dimethoxy-1,4-bis(dimethylamino)butane (DDB), and (S)-(+)-1-(2-pyrrolidinylmethyl)pyrrolidine (PMP) in toluene at −78°C. The monomer showed higher resistance against methanolysis compared with triphenylmethyl methacrylate (TrMA) and several other analogues. In the asymmetric anionic polymerization of 2F4F2PyMA, PMP was found to be a more effective chiral ligand than DDB and Sp and gave quantitatively an optically active polymer with nearly perfect isotacticity. Enantiomer selection was observed in the polymerization of racemic 2F4F2PyMA with the chiral lithium complexes. Chiral recognition ability of the optically active poly(2F4F2PyMA) was examined by an enantioselective adsorption experiment. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 2013–2019, 1998 相似文献
11.
S.K. Mehta Ganga Ram Rajat Chauhan K.K. Bhasin 《The Journal of chemical thermodynamics》2009,(12):1329-1338
The thermodynamic parameters viz. excess molar volume VE and speed of sound u, transport parameter viscosity η, and spectroscopic parameters viz. IR, 1H, 13C NMR have been measured for the mixtures of isomeric butanediol (1,2-, 1,3-, 1,4-, and 2,3-butanediol) and N-methyl-2-pyrrolidinone over the whole composition range at 308.15 K. The partial molar quantities , isentropic compressibility , viscosity deviation Δη, deviation in Gibbs free energies of activation for viscous flow g(x), and excess NMR chemical shift δE have been estimated and analyzed. Results show that the interaction between unlike molecules takes place through hydroxyl groups of isomeric butanediol and CO group of N-methyl-2-pyrrolidinone. Excellent agreement between thermodynamic and spectroscopic measurements is observed. 相似文献
12.
Damascenone 1 DORICENONE (trade mark applied for by Firmenich & Cie, Geneva). an odoriferous ketone isolated in minute amounts from Bulgarian rose oil (Rosa damascena Mill.) is shown to be trans-2,6,6-trimethyl-1-crotonoyl-cyclohexa-1, 3-diene (I). A synthesis starting from beta;-cyclocitral is described for this conspicuous constituent of rose oil, which displays a powerful fragrance. The synthesis of four related, more saturated ketones, damascones 2 DORINONE (trade mark applied for by Firmenich & Cie, Geneva). , is also described. 相似文献
13.
The interfacial tensions between polystyrene (PS) and poly(butylene terephthalate) 1 System. name: poly(tetramethylene terephthalate). (PBT), PS/poly(methyl methacrylate) (PMMA), and PBT/PMMA pairs have been obtained by employing the Neumann Triangle method (NT). The results are in good agreement with those obtained by the breaking thread method. For the first time, the NT method was applied to a reactive polymer pair with an in-situ compatibilizer to measure the interfacial tension. We found that the interfacial tension of the PS/PBT system with a small amount of poly(styrene-co-glycidyl methacrylate) 2 System. name of glycidyl: 2,3-epoxypropyl. (PS-GMA) is significantly reduced compared to that without PS-GMA. 相似文献
14.
The He(Iα) photoelectron (PE) spectra of tris(perfluorocyclobuta)benzene 4 (F) 1 3,3,4,4,7,7,8,8,11,11,12,12-Dodecafluorotetracyclo[8.2.0.02,5.06,9]dodeca-1,5,9-triene , tris(perfluorocyclopenta)benzene 5 (F) 2 1,1,2,2,3,3,4,4,5,5,6,6,7,7,8,8,9,9-Octadecafluoro-2,3,4,5,6,7,8,9-octahydro-1H-trindene. , tetrakis(perfluorocyclobuta)cyclooctatetraene 6 (F) 3 3,3,4,4,7,7,8,8,11,1l,l2,l2,l5,15,16,16-Hexadecafluoropentacyclo[12.2.0.02,5.06,9.010,13]hexadeca-1,5,9,13-tetraene. , and of tetrakis(perfluorocyclopenta)cyclooctatetraene 7 (F) 4 1,1,2,2,3,3,4,4,5,5,6,6,7,7,8,8,9,9,10,10,11,11,12,12-Tetracosafluoro-1,2,3,4,5,6,7,8,9,10,11,12-dodeca-hydrotetracyclopenta[a,c,e,g]cyclooctene. are reported. A tentative assignment of the PE spectra is derived by empirical correlation with those of relevant reference compounds. The results suggest that 6 (F) retains the D4h-conformation in the gas phase, i.e. A conformation with a planar cyclooctatetraene ring, as observed in the crystal. All four compounds exhibit a sharp increase of their first ionization energies, relative to the corresponding parent hydrocarbons, due to the perfluoro effect. 相似文献
15.
Lorenz Walder Gerhard Rytz Ulrich Vgeli Rolf Scheffold Peter Engel 《Helvetica chimica acta》1984,67(7):1801-1817
(±)-[1-hydro-8H-HDP]cobalt(I) 1 1 Full name of 1: [2,2,3,3,7,7,8,8,12,12,13,13,17,17,18,18,-hexadecamethyl-2,3,7,8,12,13,17,18,-octahydro-1H,23H-10,20-diaza-porphinato]cobalt(I); full name of 2a : dibromo[2,2,3,3,7,7,8,8,12,12,13,13,17,17,18,18-hexadecamethyl-2,3,7,8,12,13,17,18-octahydro-1H,21H-10,20-diazaporphinato]cobalt(III). 2 For the nomenclature of [HDP]-complexes see addendum in [2]. is obtained by chemical or electrochemical four-electron reduction of (±)-dibromo- or (±)-dicano[1-hydroxy-8H-HDP]cobalt(III) 2a or 2b 4, respectively. The crystal nad molecular structure of 1 was determined by combination of X-ray analysis and MS, 1H-, and 13C-NMR spectroscopy. Square-planar coordinated Co(I) lies closely to the best plane through the four N-atoms which form the first coordination sphere. Thermodynamic data for the coordination of axial bases with the cation of [1-hydroxy-8H-HDP]cobalt 2 in its different metal oxidation states were determined. The pathway of the overall four-electron reduction of 2a to 1 was elucidated: it involves a two-electron reduction of the central metal, a two-electron reduction of the macrocycle accompanied by elimination of the OH-group and final protonation at C(1). Evidence for an intramolecular electron transfer between the central metal and the macrocycle is presented. 相似文献
16.
Dieter Seebach Hans-Otto Kalinowski Bahram Bastani Gerhard Crass Hermann Daum Hennig Drr Nicolaas P. Dupreez Volker Ehrig Werner Langer Christa Nüssler Hoc-An Oei Manfred Schmidt 《Helvetica chimica acta》1977,60(2):301-325
Preparation of Auxiliaries for Asymmetric Syntheses from Tartaric Acid. Additions of Butyllithium to Aldehydes in Chiral Media. Chiral derivatives of the complexing 1,2-diheterosubstituted ethanes A–D are prepared from tartaric acid. The key starting materials are the succinic acid derivative 1 , the dioxolane 2a , and the diamide 3a . These are converted to the ethers, alkoxyamines, and alkylthio-amines listed in the first column of Table 2 which also contains the derivatives 21c, 22d , and 23d made from lactic acid, malic acid, and proline, respectively. It is shown that the highest optical yields (up to 40%) in reactions of butyllithium with aldehydes are obtained when mixtures of (?)-1,2,3,4-tetramethoxy-butane ( 4b ), (+)-2,3-dimethoxy-N,N,N′,N′-tetramethyl-1,4-butanediamine ( 17a ), and (?)-1,4-dimethoxy-N,N,N′,N′-tetramethyl-2,3-butanediamine ( 14c ) with pentane are used at temperatures down to ?150° and ratios of auxiliary/butyllithium of up to 10:1 (see equation (1), Tables 2–4). 相似文献
17.
Yansong J. Lu Bin Hu Mahavir Prashad Shaum Kabadi Oljan Repi
Thomas J. Blacklock 《Journal of heterocyclic chemistry》2006,43(4):1125-1127
18.
N. P. Gambaryan E. M. Rokhlin Yu. V. Zeifman Chen Ching-yun I. L. Knunyants 《Angewandte Chemie (International ed. in English)》1966,5(11):947-956
The chemistry of polyfluorinated ketones has recently received a great deal of attention. 1 A. Ya. Yakoubovich, Usp. Chim. 25, 3 (1956). 2 H. P. Braendlin and E. T. McBee in: Advances in Fluorine Chemistry. Butterworths, London 1963, Vol. 3, p. 1. 3 The review by Braendlin and McBee [2] does not deal only with perfluorinated ketones; moreover, though published in 1963, it is already outdated. The papers discussed in [1,2] will not be reviewed in the present article. . The carbonyl and imino groups of the fluorinated ketones and their imines react in many different ways. In particular, the electron-attracting perfluoroalkyl groups intensify the electrophilic properties and weaken the nucleophilic properties of the carbonyl group. The perfluoroalkyl group also hinders the heterolytic removal of the hydroxyl group from adducts by reducing the stability of the carbonium ion . The increased electrophilicity of the carbonyl group and the increased stability of the addition products leads not only to a change in reactivity in the characteristic ketone reactions, but also to numerous new reactions which are not observed with non-fluorinated ketones. Thus it is possible to synthesize a wide variety of fluoroorganic compounds from perfluorinated ketones. 4 We have been concerned mainly with hexafluoroacetone, since in addition to being the most readily available and simplest perfluorinated ketone, this is also a typical representative of this class of compounds. . 相似文献
19.
Kyriacos C. Nicolaou Rodney K. Guy 《Angewandte Chemie (International ed. in English)》1995,34(19):2079-2090
Much has been written about taxol, one of the newest weapons against cancer, and its producer, the Pacific Yew tree (Taxus brevifolia). 1 K. C. Nicolaou, W.-M. Dai, R. K. Guy, Angew. Chem. 1994, 106, 38–69; Angew. Chem. Int. Ed. Engl. 1994, 33, 15–44. In this article, the authors give a frank and behind-the-scenes account of their encounter with this well-known molecule, which they and their collaborators faced as a synthetic target. 2 K. C. Nicolaou, Z. Yang, J.-J. Liu, H. Ueno, P. G. Nantermet, R. K. Guy, C. F. Claiborne, J. Renaud, E. A. Couladouros, K. Paulvannan, E. J. Sorensen, Nature (London) 1994, 367, 630–634. 3 K. C. Nicolaou, J.-J. Liu, Z. Yang, H. Ueno, R. K. Guy, E. A. Couladouros, E. J. Sorensen, J. Am. Chem. Soc. 1995, 117, 624–633. 4 K. C. Nicolaou, J.-J. Liu, Z. Yang, H. Ueno, E. J. Sorensen, C. F. Claiborne, R. K. Guy, C.-K. Hwang, M. Nakada, P. G. Nantermet, J. Am. Chem. Soc. 1995, 117, 634–644. 5 K. C. Nicolaou, Z. Yang, J.-J. Liu, P. G. Nantermet, C. F. Claiborne, J. Renaud, R. K. Guy, K. Shibayama, J. Am. Chem. Soc. 1995, 117, 645–652. 6 K. C. Nicolaou, H. Ueno, J.-J. Liu, P. G. Nantermet, Z. Yang, J. Renaud, K. Paulvannan, R. Chadha, J. Am. Chem. Soc. 1995, 117, 653–659. Once again total synthesis is found to offer excellent opportunities for developing new synthetic strategies and novel reactions. The team of chemists who took up this challenge emerged with valuable experience and confidence in their skills. 相似文献
20.
Stefan Matile Agnes Janowitz Sandro Ghirlanda Annalaura Lorenzi-Riatsch Albert Horni Attila Moricz Stefan Bienz Norbert Bild Wolf-Dietrich Woggon Manfred Hesse 《Helvetica chimica acta》1993,76(3):1305-1310
Neighboring-Group Participation in the Gas Phase: Intramolecular Deacetalization of Hydroxyacetals under the Conditions of Chemical Ionization 1 Herrn Prof. Dr. Christoph Tamm zum 70. Geburtstag gewidmet Under the conditions of chemical ionization (NH3, isobutane, ND3), hydroxyacetals do not show the expected [M + H+] signal, but the peak corresponding to the loss of the alcohol component of the acetal. This reaction is dependent on the presence of the OH group in the vicinity of the acetal and on the ring size of the heterocycle being formed. M+· is detected to a small extent as a consequence of charge exchange during chemical ionization. 相似文献