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Molecules, Volume 6, Issue 11 (November 2001) – 9 articles , Pages 845-926

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Research

81 KiB  
Article
Mg2+-Imidazole-Catalyzed Self-Condensation of Malonyl Thioesters: Getting Tuned for Biomimetic Polyketide Synthesis?
by Naomi Sakai, Nathalie Sordé and Stefan Matile
Molecules 2001, 6(11), 845-851; https://doi.org/10.3390/61100845 - 31 Oct 2001
Cited by 21 | Viewed by 9108
Abstract
We report that a subtle balance of carbanion reactivity, leaving group activation, and pKa of the catalyst is required for efficient self-condensation of thiomalonates to thioacetoacetates in up to 71% yield under “biomimetic” conditions originally proposed by Kobuke and Yoshida (Tetrahedron Lett [...] Read more.
We report that a subtle balance of carbanion reactivity, leaving group activation, and pKa of the catalyst is required for efficient self-condensation of thiomalonates to thioacetoacetates in up to 71% yield under “biomimetic” conditions originally proposed by Kobuke and Yoshida (Tetrahedron Lett. 1978, 19, 367). Full article
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95 KiB  
Article
Amine and Titanium (IV) Chloride, Boron (III) Chloride or Zirconium (IV) Chloride-Promoted Baylis-Hillman Reactions
by Min Shi, Jian-Kang Jiang and Shi-Cong Cui
Molecules 2001, 6(11), 852-868; https://doi.org/10.3390/61100852 - 31 Oct 2001
Cited by 21 | Viewed by 11604
Abstract
The Baylis-Hillman reactions of various aryl aldehydes with methyl vinyl ketone at temperatures below -20oC using Lewis acids such as titanium (IV) chloride, boron (III) chloride or zirconium (IV) chloride in the presence of a catalytic amount of selected amines used as a [...] Read more.
The Baylis-Hillman reactions of various aryl aldehydes with methyl vinyl ketone at temperatures below -20oC using Lewis acids such as titanium (IV) chloride, boron (III) chloride or zirconium (IV) chloride in the presence of a catalytic amount of selected amines used as a Lewis bases afford the chlorinated compounds 1 as the major product in very high yields. Acrylonitrile can also undergo the same reaction to give the corresponding chlorinated product in moderate yield. A plausible reaction mechanism is proposed. However, if the reaction was carried out at room temperature (ca. 20oC), then the Z-configuration of the elimination product 3, derived from 1, was formed as the major product. Full article
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33 KiB  
Article
One-Pot Procedures for Preparing (Dichloroiodo)arenes from Arenes and Diiodine, with Chromium(VI) Oxide as the Oxidant
by Nicolas Obeid and Lech Skulski
Molecules 2001, 6(11), 869-874; https://doi.org/10.3390/61100869 - 31 Oct 2001
Cited by 12 | Viewed by 6508
Abstract
Ten representative (dichloroiodo)arenes, ArICl2, were prepared from the corresponding arenes and diiodine in variable anhydrous mixtures, ArH/I2/CrO3/AcOH/Ac2O/conc. H2SO4, followed by the addition of conc. hydrochloric acid, used as the source of [...] Read more.
Ten representative (dichloroiodo)arenes, ArICl2, were prepared from the corresponding arenes and diiodine in variable anhydrous mixtures, ArH/I2/CrO3/AcOH/Ac2O/conc. H2SO4, followed by the addition of conc. hydrochloric acid, used as the source of chlorine; ArICl2 are useful in organic synthesis as mild and selective chlorinating and/or oxidizing agents. Full article
35 KiB  
Article
One-Pot Preparations of Diaryliodonium Bromides from Iodoarenes and Arenes, with Sodium Perborate as the Oxidant
by Anna Kryska and Lech Skulski
Molecules 2001, 6(11), 875-880; https://doi.org/10.3390/61100875 - 31 Oct 2001
Cited by 19 | Viewed by 8326
Abstract
This paper reports a one-pot synthesis of the title bromides from both activated and deactivated iodoarenes which are first oxidized with anhydrous NaBO3·H2O/Ac2O/conc.H2SO4 liquid mixtures, then coupled in situ with benzene and activated arenes [...] Read more.
This paper reports a one-pot synthesis of the title bromides from both activated and deactivated iodoarenes which are first oxidized with anhydrous NaBO3·H2O/Ac2O/conc.H2SO4 liquid mixtures, then coupled in situ with benzene and activated arenes and, finally, precipitated out with a KBr solution; this method is easy, cheap, safe and fairly effective. Full article
103 KiB  
Article
Syntheses of (Diacetoxyiodo)arenes or Iodylarenes from Iodoarenes, with Sodium Periodate as the Oxidant
by Pawel Kazmierczak, Lech Skulski and Lukasz Kraszkiewicz
Molecules 2001, 6(11), 881-891; https://doi.org/10.3390/61100881 - 31 Oct 2001
Cited by 76 | Viewed by 13515
Abstract
- Easy, safe, and effective novel methods for preparing either (diacetoxyiodo)-arenes, ArI(OAc)2, or iodylarenes, ArIO2, from the corresponding iodoarenes, ArI, using sodium periodate as the oxidant are presented in this paper. In order to obtain 2- and 4-iodylbenzoic acids, [...] Read more.
- Easy, safe, and effective novel methods for preparing either (diacetoxyiodo)-arenes, ArI(OAc)2, or iodylarenes, ArIO2, from the corresponding iodoarenes, ArI, using sodium periodate as the oxidant are presented in this paper. In order to obtain 2- and 4-iodylbenzoic acids, the respective sodium salts of 2- and 4-iodobenzoic acids should be used as the starting substrates, because mixtures containing the corresponding iodosyl derivatives as the main products along with the intended iodyl compounds are produced from the free parent acids. Full article
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119 KiB  
Article
Captodative Formyl Enamines in a New Synthesis of Tertiary α-Amino Esters
by Alexandre Yu. Rulev, Lyudmila I. Larina and Mikhail G. Voronkov
Molecules 2001, 6(11), 892-899; https://doi.org/10.3390/61100892 - 31 Oct 2001
Cited by 13 | Viewed by 7763
Abstract
A strategy to create the –CH(NR2)CO- moiety from captodative formyl enamines was successfully applied to the synthesis of tertiary α-amino esters. Full article
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81 KiB  
Article
Efficient, Solvent-Free Oxidation of Organic Compounds with Potassium Dichromate in the Presence of Lewis Acids
by Iraj Mohammadpoor-Baltork, Majid M. Sadeghi and Abol-Hassan Adibi
Molecules 2001, 6(11), 900-908; https://doi.org/10.3390/61100900 - 31 Oct 2001
Cited by 31 | Viewed by 8499
Abstract
The synthetic utility of potassium dichromate in the presence of Lewis acids under solid phase conditions is described. This reagent efficiently oxidizes alcohols, acyloins, oximes and semicarbazones to their corresponding carbonyl compounds, while trimethylsilyl and tetrahydropyranyl ethers, ethylene acetals and ketals undergo oxidative [...] Read more.
The synthetic utility of potassium dichromate in the presence of Lewis acids under solid phase conditions is described. This reagent efficiently oxidizes alcohols, acyloins, oximes and semicarbazones to their corresponding carbonyl compounds, while trimethylsilyl and tetrahydropyranyl ethers, ethylene acetals and ketals undergo oxidative deprotection to produce carbonyl compounds efficiently. Full article
172 KiB  
Article
Synthesis and Crystal Structure Determination of a Nickel(II) Complex of an Acyclic Pentadentate (N5) Mono Schiff Base Ligand
by Hassan Keypour, Sadegh Salehzadeh, R. G. Pritchard and R. V. Parish
Molecules 2001, 6(11), 909-914; https://doi.org/10.3390/61100909 - 31 Oct 2001
Cited by 9 | Viewed by 8826
Abstract
The asymmetrical tripodal tetraamine ligand N[(CH2)3NH2]2[(CH2)2NH2] (ppe) was condensed with 2-acetylpyridine in the presence of nickel(II) ion. In ethanolwater solution the reaction stops after the first stage of condensation, [...] Read more.
The asymmetrical tripodal tetraamine ligand N[(CH2)3NH2]2[(CH2)2NH2] (ppe) was condensed with 2-acetylpyridine in the presence of nickel(II) ion. In ethanolwater solution the reaction stops after the first stage of condensation, and a new nickel(II) complex of an acyclic pentadentate (N5) mono Schiff base ligand was obtained. X-ray structure analysis of the resulting complex, [Ni(ppe-py)(H2O)](ClO4)2, indicates that condensation with 2-acetylpyridine is at the propylene chain of ppe. The geometry around the nickel ion is distorted octahedral in which the sixth co-ordination group is a solvent molecule. Full article
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59 KiB  
Article
A New Effective Algorithm for the Unambiguous Identification of the Stereochemical Characteristics of Compounds During Their Registration in Databases
by T. Cieplak and J. L. Wisniewski
Molecules 2001, 6(11), 915-926; https://doi.org/10.3390/61100915 - 31 Oct 2001
Cited by 12 | Viewed by 8162
Abstract
A new effective algorithm for handling of geometry at chiral centers for the processing of stereochemical structures during their unambiguous registration in databases was designed, programmed and implemented. The chemical and mathematical reasoning behind the algorithm are discussed in detail. Its advantages- in [...] Read more.
A new effective algorithm for handling of geometry at chiral centers for the processing of stereochemical structures during their unambiguous registration in databases was designed, programmed and implemented. The chemical and mathematical reasoning behind the algorithm are discussed in detail. Its advantages- in comparison to the methods used so far - are illustrated for the manual as well as for the computerassisted assignment of stereodescriptors based on the CIP ranking procedure. Full article
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