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First Representative (first + representative)
Selected AbstractsUnprecedented [2 + 2]-Cyclodimerization of 1-Aza-1,3,4-trienes: First Representative of 3,4-Diisopropylidenecyclobutane-1,2-dicarbimidothioates.CHEMINFORM, Issue 35 2007N. A. Nedolya Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF. [source] ChemInform Abstract: Synthesis of Benzo[b]thieno[3,2-e]benzimidazoles, First Representatives of a New Heterocyclic System.CHEMINFORM, Issue 23 2009T. E. Khoshtariya Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] ChemInform Abstract: Synthesis and Properties of the First Representatives of Terminal Acetylenes in 3-Imidazoline-1-oxyl 3-Oxide Series (IV) and (VIII).CHEMINFORM, Issue 34 2008O. L. Krivenko Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] Synthesis of the First Representatives of Benzanellated Dihydroselenochromenes.CHEMINFORM, Issue 26 2007Ya. B. Drevko Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF. [source] ChemInform Abstract: Synthesis of the First Representatives of 3-Ethynyldiaziridines.CHEMINFORM, Issue 23 2002Nina N. Makhova Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] Heddleichthys, a new tristichopterid genus from the Dura Den Formation, Midland Valley, Scotland (Famennian, Late Devonian)ACTA ZOOLOGICA, Issue 2009Daniel Snitting Abstract A new tristichopterid genus, Heddleichthys, from the Famennian of Scotland is described based on material previously assigned to a number of different genera, including Glyptopomus, Gyroptychius and Eusthenopteron. The validity of the new genus is established by a discussion of the reasons for the invalidity of the previous assignments. Heddleichthys is characterized by a combination of derived and primitive tristichopterid features. Derived features include the presence of symphyseal dentary fangs and premaxillary pseudofangs, a diamond-shaped symmetric caudal fin, a low posterodorsal expansion of the maxilla, and a posteriorly positioned kite-shaped pineal series. Primitive features include a postorbital and jugal contribution to the orbital margin and a parasphenoid with a ventral keel. External dermal bones are rather poorly preserved in the referred material, with few easily discernible sutures. The holotype specimen, a three-dimensionally preserved skull, was scanned by computed tomography to reveal well-preserved internal dermal bones, including entopterygoids, vomers and parasphenoid. There is no preserved endoskeletal material. As the first representative of derived tristichopterids described from Britain, Heddleichthys lends support to the idea that faunal dispersion between Gondwana and Laurussia in the Late Devonian was widespread. Derived tristichopterids have been described from all continents except South America. In contrast, the basal tristichopterids Eusthenopteron and Tristichopterus are still only described from Laurussia. [source] Crystal Structure of Garciniaphenone and Evidences on the Relationship between Keto,Enol Tautomerism and ConfigurationHELVETICA CHIMICA ACTA, Issue 7 2008Felipe Abstract Garciniaphenone (=rel- (1R,5R,7R)-3-benzoyl-4-hydroxy-8,8-dimethyl-1,7-bis(3-methylbut-2-en-1-yl)bicyclo[3.3.1]non-3-ene-2,9-dione; 1), a novel natural product, was isolated from a hexane extract of Garcinia brasiliensis fruits. The crystal structure of 1 as well as the selected geometrical and configurational features were compared with those of known related polyprenylated benzophenones. Garciniaphenone is the first representative of polyprenylated benzophenones without a prenyl substituent at C(5). Notably, the absence of a 5-prenyl substituent has an impact on the molecular geometry. The tautomeric form of 1 in the solid state was readily established by a residual-electronic-density map generated by means of a difference Fourier analysis, and there is an entirely delocalized six-membered chelate ring encompassing the keto,enol moiety. The configuration at C(7) was used to rationalize the nature of the keto,enol tautomeric form within 1. The intermolecular array in the network is maintained by nonclassical intermolecular H-bonds. [source] Bioinspired Materials: Oligothiophene Versus , -Sheet Peptide: Synthesis and Self-Assembly of an Organic Semiconductor-Peptide Hybrid (Adv. Mater.ADVANCED MATERIALS, Issue 16 200916/2009) A first representative of a novel class of bioinspired materials, a fully symmetric hybrid between an oligothiophene and a , -sheet peptide, is introduced in work by Peter Bäuerle and co-workers on p. 1562. The conjugate can be synthesized via click-chemistry and employs a switch-peptide segment to gain control over the self-assembly motif of the peptide part. [source] Oligothiophene Versus , -Sheet Peptide: Synthesis and Self-Assembly of an Organic Semiconductor-Peptide HybridADVANCED MATERIALS, Issue 16 2009Eva-Kathrin Schillinger A first representative of a novel class of bioinspired materials is introduced, a fully symmetric hybrid between an oligothiophene and a , -sheet peptide. The conjugate is synthesized via "click chemistry", and employs a switch-peptide segment to gain control over the self-assembly motif of the peptide part. The self-organization properties of the hybrid are investigated. [source] A rhabdocoel turbellarian (Platyhelminthes, Typhloplanoida) in Baltic amber with a review of fossil and sub-fossil platyhelminthsINVERTEBRATE BIOLOGY, Issue 4 2003George Poinar Jr. Abstract. Palaeosoma balticus n. g., n. sp. (Rhabdocoela, Typhloplanoida), the oldest body fossil of a turbellarian and the first representative of the phylum Platyhelminthes found in fossilized resin, is described from Baltic amber 40 million years old. Characters of the fossil turbellarian are epidermal cilia, rhabdoids, a rosulate pharynx, adhesive papillae, and sensory bristles. The body cavity contains developing eggs or capsules. The fossil demonstrates that rhabdocoels had developed a terrestrial habit and were producing subitaneous eggs by the Eocene. A summary of the fossil and sub-fossil records of platyhelminths is presented. [source] A New Class of Binuclear Gallium Hydrides: Synthesis and Properties of [{GaCl(hpp)H}2] (hpp=1,3,4,6,7,8-Hexahydro-2H -pyrimido[1,2- a]pyrimidate)CHEMISTRY - A EUROPEAN JOURNAL, Issue 9 2007George Robinson Abstract Herein we report on the synthesis and characterization of the first representative of a new class of gallium hydrides, namely [{GaCl(hpp)H}2] (hpp=1,3,4,6,7,8-hexahydro-2H -pyrimido[1,2- a]pyrimidate). Our X-ray diffraction data suggest the presence of weak HH contacts between adjacent [{GaCl(hpp)H}2] molecules in the crystal. With the aid of quantum-chemical calculations, the pathway of its formation starting with the adduct H2ClGa,NMe3 and the pyrimidine hppH were analyzed. [{GaCl(hpp)H}2] slowly decomposes at 25,°C, a process which presumably leads under H2 elimination to [{GaCl(hpp)}2]. Although we were not yet able to characterize [{GaCl(hpp)}2] experimentally, DFT calculations provide information about its likely structure. According to these calculations, the molecule features a GaGa single bond. [source] Betaine Adducts of N-Heterocyclic Carbenes: Synthesis, Properties, and ReactivityEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 13 2009Lionel Delaude Abstract N-Heterocyclic carbenes (NHCs) form stable zwitterionicadducts with a range of heteroallenes, ketenes, and allenes. Although the first representatives of this class of inner salts were first investigated as far back as the 1960s, they have enjoyed a sustained interest from the chemical community over the years. Depending on the nature of their anionic moiety, NHC betaines display a very broad palette of reactivities and have found applications in various fields of organic synthesis and catalysis. In this Microreview, the synthesis, properties, and reactivity of NHC betaines are surveyed. The NHCs under consideration include ylidenes derived from imidazole, benzimidazole, imidazoline, thiazole, or triazole, and the heteroallenes investigated so far are carbon dioxide, carbon disulfide, isocyanates, isothiocyanates, and their selenium analogues. A historical background is provided for each type of adduct under consideration, but emphasis is placed mainly on developments that have appeared in the literature within the past few years. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source] Synthesis of (1,2,4-Oxadiazole)palladium(II) Complexes by [2 + 3] Cycloaddition of Nitrile Oxides to Organonitriles in the Presence of PdCl2EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 5 2005Nadezhda A. Bokach Abstract The reaction between the nitrile oxides 2,4,6-R3C6H2CNO (R = Me, OMe) and trans -[PdCl2(RCN)2], or RCN (R = Me, Et, CH2CN, NMe2, Ph) in the presence of PdCl2, proceeded smoothly under mild conditions and allowed the isolation of the 1,2,4-oxadiazole complexes trans -[PdCl2{Na=C(R)-ON=Cb(C6H2R3)(Na,Cb)}2] (1,8) in 40,85,% yields. In CH2Cl2, the reaction between 2,4,6-R3C6H2CNO and [PdCl2(MeCN)2] furnishes [PdCl2(ONCC6H2R3)2] (9 and 10), which are the first representatives of metal compounds where nitrile oxides act as ligands. The 1,2,4-oxadiazole complexes 1,8 were characterized by elemental analysis, FAB mass spectrometry, and IR, 1H and 13C{1H} NMR spectroscopy, while 2, 3, 7, and 8 were additionally characterized by X-ray crystallography. The liberation of the heterocyclic species from 1,8 was successfully performed by substitution reaction either with 1,2-bis(diphenylphosphanyl)ethane or with an excess amount of Na2S·7H2O in MeOH; the liberated 1,2,4-oxadiazoles (11,18) were characterized by positive-ion FAB mass spectrometry and 1H and 13C{1H} NMR spectroscopy. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005) [source] Synthesis and Conformational Analysis of Tetrahydroisoquinoline-Fused 1,3,2-Oxazaphospholidines and 1,2,3-OxathiazolidinesEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 8 2008Ildikó Schuster Abstract The cyclizations of tetrahydroisoquinoline 1,2-amino alcohols with phenylphosphonic dichloride, bis(2-chloroethyl)phosphoramidic dichloride, thionyl chloride and sulfuryl chloride were utilized to synthesize 1,5,6,10b-tetrahydro-1,3,2-oxazaphospholo[4,3- a]isoquinolines (2, 3), 1,5,10,10a-tetrahydro-1,3,2-oxazaphospholo[3,4- b]isoquinolines (8, 9), 1,5,6,10b-tetrahydro-1,2,3-oxathiazolo[4,3- a]isoquinolines (4,6) anda 1,5,10,10a-tetrahydro-1,2,3-oxathiazolo[3,4- b]isoquinoline (11), which are the first representatives of these ring systems. NMR spectroscopic analysis revealed the existence of conformational equilibria that are fast on the NMR timescale. Theoretical DFT calculations pointed to the participation of generally two preferred conformers in the conformational equilibria; the positions of the equilibria were indicated by the experimental NMR spectroscopic parameters, and they are in good agreement with the theoretically calculated energy differences of the participating conformers. For two compounds, which could be not isolated (10, 12), both the preferred conformers and the stereochemistry could be concluded from the DFT calculation results. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source] Phosphorylation of N -Silylpyrroles with Phosphorus TribromideHETEROATOM CHEMISTRY, Issue 1 2008Aleksandra A. Chaikovskaya Phosphorylation of N -trimethylsilyl- and N -dimethyl-tert-butylsilylpyrroles with phosphorus tribromide in pyridine proceeds selectively at position 3 of the pyrrole ring. Removal of the trialkylsilyl protecting group has furnished the first representatives of N -unsubstituted 3-phosphorylated pyrroles. © 2008 Wiley Periodicals, Inc. Heteroatom Chem 19:93,96, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.20416 [source] New Structural Features in Heavy Alkaline Earth-Metal Chemistry , Molecular Heterobimetallic Group,1, Ba ComplexesCHEMISTRY - A EUROPEAN JOURNAL, Issue 7 2007Felisa Zuniga, Maria Abstract The preparation of heterobimetallic complexes consisting of alkali and heavy alkaline earth metals remains a challenge due to limited available synthetic strategies. Here we present a new class of group,1, Ba compounds of the type [Mn{Ba(Odpp)2+n}] (M=Na(n=1) (1), K(n=1) (2), Cs(n=1) (3), Li(n=2) (4); HOdpp=2,6-diphenylphenol) and the Lewis base adducts [Li2(thf)2{Ba(Odpp)4}],PhMe (5) and [K{Ba(Odpp)3(diglyme)}] (6) (diglyme=[bis(2-methoxy)ethyl ether]) as the first representatives of heterobimetallic group,1, Ba species of low nuclearity. The compounds display a significant degree of metal,arene interaction, believed to be a key factor in stabilizing these highly reactive species. Obtained by solid-state direct metalation, the target compounds are available without further work-up. [source] | |||||||||||||||||||||||||