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Ring Compounds (ring + compound)
Selected AbstractsEfficient Access to Fused Ring Compounds via Dearomatization/Ring-Closing Metathesis.CHEMINFORM, Issue 15 2004E. Peter Kuendig Abstract For Abstract see ChemInform Abstract in Full Text. [source] Alkyne and Ketone Induced Novel Cleavage of a C,C Bond and a C,Si Bond in Zirconacyclobutene,Silacyclobutene Fused Ring Compounds.CHEMINFORM, Issue 18 2003Tao Yu Abstract For Abstract see ChemInform Abstract in Full Text. [source] ChemInform Abstract: Synthesis and Structures of Novel Ring Compounds of Bismuth with Tris(trimethylsilyl)silyl and -stannyl Substituents , [(Me3Si)3Si]4Bi4 and [(Me3Si)3Sn]6Bi8CHEMINFORM, Issue 12 2002Gerald Linti 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] New Aspects in the Chemistry of Three-membered Ring Compounds Containing a Highly Coordinate Main Group ElementCHINESE JOURNAL OF CHEMISTRY, Issue 9 2005Kawashima Takayuki Abstract The title compounds were synthesized by taking advantage of the Martin ligand. Their structures were determined by X-ray crystallography. Pentacoordinate thiasiliranides were hydrolyzed to give the corresponding thiol. Pentacoordinate chalcogenaphosphiranes were found to have polar P-chalcogen bonds, which were confirmed by their reactions with CF 3SO3Me to give the corresponding 1-(methylchalcogena)alkylphosphonium triflates and by the solvent-dependent NMR studies. [source] A Rearrangement of Azobenzene upon Interaction with an Aluminum(I) Monomer LAl {L = HC[(CMe)(NAr)]2, Ar = 2,6- iPr2C6H3}EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 11 2005Hongping Zhu Abstract Reaction of LAl (1) or [LAl{,2 -C2(SiMe3)2}] (2) {L = HC[(CMe)(NAr)]2, Ar = 2,6- iPr2C6H3} with azobenzene affords a five-membered ring compound [LAl{N(H)- o -C6H4N(Ph)}] (3). In the formation of 3 a three-membered intermediate [LAl(,2 -N2Ph2)] (A) is suggested by a [1 + 2] cycloaddition reaction; A is not stable and further rearranges to 3. DFT calculations on similar compounds with modified L' {L' = HC[(CMe)(NPh)]2} show that the complexation energy of the reaction of L'Al with azobenzene to form [L'Al(,2 -N2Ph2)] is about,39 kcal,mol,1, and the best estimate of the energy difference between [L'Al(,2 -N2Ph2)] and [L'Al{N(H)- o -C6H4N(Ph)}] is,76 kcal,mol,1. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005) [source] Synthesis of a Hexadentate Hexameric Aluminum Imide and Its Metathesis ReactionsEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 3 2003N. Dastagiri Reddy Abstract The reaction of AlH3·NMe3 with one equivalent of 2-cyanothiophene in toluene afforded [HAlNCH2(C4H3S)]6 (2) in good yield. Treatment of 2 with SiMe3Br and SiMe3Cl in toluene under refluxing conditions resulted in the formation of compounds [BrAlNCH2(C4H3S)]6 (3) and [ClAlNCH2(C4H3S)]6 (4), respectively. In a similar way [PhC,CAlNCH2(C4H3S)]6 (5) was readily obtained from the reaction between 2 and PhC,CH. When 2 was treated with PhSH the Al-N cluster core dissociated and a four-membered ring compound [(PhS)2AlNHCH2(C4H3S)]2 (6) was formed. In contrast, a similar hexameric aluminum imide (HAlNCH2Ph)6 (1) retains its Al-N network when treated with PhSH to yield (PhSAlNCH2Ph)6 (7). An exchange of ethyl groups and hydrides occurred when 2 was treated with excess of ZnEt2, forming [EtAlNCH2(C4H3S)]68. Compounds 2,4 and 6,8 were characterized by X-ray single-crystal analysis. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003) [source] Formation and x-ray crystallographic analysis of a 1,2,5 -oxaphosphol-5(2H)-oneHETEROATOM CHEMISTRY, Issue 4 2001Naokazu Kano Reaction of an iminophosphorane 2 bearing the Martin ligand with dimethyl acetylenedicarboxylate, followed by a ring opening reaction of a [2+2]-cycloadduct between them, gave the corresponding ,-iminoalkylidenephosphorane 3, which was hydrolyzed to afford 1,2,5 -oxaphosphol-5(2H)-one 4. The structure of the novel five-membered ring compound 4 was established by X-ray crystallographic analysis. © 2001 John Wiley & Sons, Inc. Heteroatom Chem 12:282,286, 2001 [source] Theoretical studies on four-membered ring compounds with NF2, ONO2, N3, and NO2 groupsJOURNAL OF COMPUTATIONAL CHEMISTRY, Issue 4 2008Xiao-Wei Fan Abstract Density functional theory (DFT) method has been employed to study the geometric and electronic structures of a series of four-membered ring compounds at the B3LYP/6-311G** and the B3P86/6-311G** levels. In the isodesmic reactions designed for the computation of heats of formation (HOFs), 3,3-dimethyl-oxetane, azetidine, and cyclobutane were chosen as reference compounds. The HOFs for N3 substituted derivations are larger than those of oxetane compounds with ONO2 and/or NF2 substituent groups. The HOFs for oxetane with ONO2 and/or NF2 substituent groups are negative, while the HOFs for N3 substituted derivations are positive. For azetidine compounds, the substituent groups within the azetidine ring affect the HOFs, which increase as the difluoroamino group being replaced by the nitro group. The magnitudes of intramolecular group interactions were predicted through the disproportionation energies. The strain energy (SE) for the title compounds has been calculated using homodesmotic reactions. For azetidine compounds, the NF2 group connecting N atom in the ring decrease the SE of title compounds. Thermal stability were evaluated via bond dissociation energies (BDE) at the UB3LYP/6-311G** level. For the oxetane compounds, the ONO2 bond is easier to break than that of the ring CC bond. For the azetidine and cyclobutane compounds, the homolysises of CNX2 and/or NNX2 (X = O, F) bonds are primary step for bond dissociation. Detonation properties of the title compounds were evaluated by using the Kamlet,Jacobs equation based on the calculated densities and HOFs. It is found that 1,1-dinitro-3,3-bis(difluoroamino)-cyclobutane, with predicted density of ca. 1.9 g/cm3, detonation velocity (D) over 9 km/s, and detonation pressure (P) of 41 GPa that are lager than those of TNAZ, is expected to be a novel candidate of high energy density materials (HEDMs). The detonation data of nitro-BDFAA and TNCB are also close to the requirements for HEDMs. © 2007 Wiley Periodicals, Inc. J Comput Chem, 2008 [source] Mechanistic insights into oxidosqualene cyclizations through homology modelingJOURNAL OF COMPUTATIONAL CHEMISTRY, Issue 6 2003Gasch, Tanja Schulz Abstract 2,3-Oxidosqualene cyclases (OSC) are key enzymes in sterol biosynthesis. They catalyze the stereoselective cyclization and skeletal rearrangement of (3S)-2,3-oxidosqualene to lanosterol in mammals and fungi and to cycloartenol in algae and higher plants. Sequence information and proposed mechanism of 2,3-oxidosqualene cyclases are closely related to those of squalene-hopene cyclases (SHC), which represent functional analogs of OSCs in bacteria. SHCs catalyze the cationic cyclization cascade converting the linear triterpene squalene to fused ring compounds called hopanoids. High stereoselectivity and precision of the skeletal rearrangements has aroused the interest of researchers for nearly half a century, and valuable data on studying mechanistic details in the complex enzyme-catalyzed cyclization cascade has been collected. Today, interest in cyclases is still unbroken, because OSCs became targets for the development of antifungal and hypocholesterolemic drugs. However, due to the large size and membrane-bound nature of OSCs, three-dimensional structural information is still not available, thus preventing a complete understanding of the atomic details of the catalytic mechanism. In this work, we discuss results gained from homology modeling of human OSC based on structural information of SHC from Alicyclobacillus acidocaldarius and propose a structural model of human OSC. The model is in accordance with previously performed experimental studies with mechanism-based suicide inhibitors and mutagenesis experiments with altered activity and product specificity. Structural insight should strongly stimulate structure-based design of antifungal or cholesterol-lowering drugs. © 2003 Wiley Periodicals, Inc. J Comput Chem 24: 741,753, 2003 [source] Recent cancer drug development with xanthone structuresJOURNAL OF PHARMACY AND PHARMACOLOGY: AN INTERNATI ONAL JOURNAL OF PHARMACEUTICAL SCIENCE, Issue 6 2009Younghwa Na Abstract Objectives Xanthones are simple three-membered ring compounds that are mainly found as secondary metabolites in higher plants and microorganisms. Xanthones have very diverse biological profiles, including antihypertensive, antioxidative, antithrombotic and anticancer activity, depending on their diverse structures, which are modified by substituents on the ring system. Although several reviews have already been published on xanthone compounds, few of them have focused on the anticancer activity of xanthone derivatives. In this review we briefly summarize natural and synthetic xanthone compounds which have potential as anticancer drugs. Key findings The interesting structural scaffold and pharmacological importance of xanthone derivatives have led many scientists to isolate or synthesize these compounds as novel drug candidates. In the past, extensive research has been conducted to obtain xanthone derivatives from natural resources as well as through synthetic chemistry. Xanthones interact with various pharmacological targets based on the different substituents on the core ring. The anticancer activities of xanthones are also dramatically altered by the ring substituents and their positions. Summary The biological activities of synthetic xanthone derivatives depend on the various substituents and their position. Study of the biological mechanism of action of xanthone analogues, however, has not been conducted extensively compared to the diversity of xanthone compounds. Elucidation of the exact biological target of xanthone compounds will provide better opportunities for these compounds to be developed as potent anticancer drugs. At the same time, modification of natural xanthone derivatives aimed at specific targets is capable of expanding the biological spectrum of xanthone compounds. [source] The roles of plant phenolics in defence and communication during Agrobacterium and Rhizobium infectionMOLECULAR PLANT PATHOLOGY, Issue 5 2010AMITA BHATTACHARYA SUMMARY Phenolics are aromatic benzene ring compounds with one or more hydroxyl groups produced by plants mainly for protection against stress. The functions of phenolic compounds in plant physiology and interactions with biotic and abiotic environments are difficult to overestimate. Phenolics play important roles in plant development, particularly in lignin and pigment biosynthesis. They also provide structural integrity and scaffolding support to plants. Importantly, phenolic phytoalexins, secreted by wounded or otherwise perturbed plants, repel or kill many microorganisms, and some pathogens can counteract or nullify these defences or even subvert them to their own advantage. In this review, we discuss the roles of phenolics in the interactions of plants with Agrobacterium and Rhizobium. [source] Carbonyl group-containing organometallic intramolecular-coordination five-membered ring compoundsAPPLIED ORGANOMETALLIC CHEMISTRY, Issue 5 2010Iwao Omae Abstract Carbonyl group-containing organometallic intramolecular-coordination five-membered ring compounds are easily synthesized by the following five reaction methods: (1) cyclometalation, especially, orthometalation reactions; (2) the reactions of the moieties of an unsaturated carboncarbon bond attached to a carbonyl group (CCCO, CCCO); (3) the reactions of an unsaturated carboncarbon bond with carbon monoxide (CC and CO, CC and CO); (4) carbonylative ring expansion reactions; and (5) others. These compounds are very easily and regio-specifically synthesized with many kinds of metal compounds, including both transition metals and main group metals. Many of such the reactions are easily applied to organic syntheses. Copyright © 2010 John Wiley & Sons, Ltd. [source] | ||||||||||