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Aryl Substituents (aryl + substituent)
Selected AbstractsFirst-Row Transition Metal Bis(amidinate) Complexes; Planar Four-Coordination of FeII Enforced by Sterically Demanding Aryl SubstituentsEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 11 2005Christian A. Nijhuis Abstract The sterically hindered benzamidinate ligand [PhC(NAr)2], (Ar = 2,6- iPr2C6H3) has been employed to prepare bis(amidinate) complexes [{PhC(NAr)2}2M] of the divalent first-row transition metals Cr,Ni (1,5). For Cr (planar), Mn and Co (tetrahedral) the observed structures follow the electronic preference for the metal ion in its highest spin multiplicity, as determined by DFT calculations. Remarkably, the Fe derivative adopts a distorted planar structure while retaining the high-spin (S = 2) configuration. This rare combination is due to reduced interligand steric interactions in the planar vs. the tetrahedral structure, combined with a relatively small electronic preference of FeII for the tetrahedral environment. Thus, the simple bidentate ligand N,N' -diarylbenzamidinate provides a convenient means to make this unusual species accessible for further study. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005) [source] ChemInform Abstract: Chiral Pyridyl Phosphinites with Large Aryl Substituents as Efficient Ligands for the Asymmetric Iridium-Catalyzed Hydrogenation of Difficult Substrates.CHEMINFORM, Issue 41 2010David H. Woodmansee No abstract is available for this article. [source] Structural Diversity in Organotin Compounds Derived from Bulky Monoaryl Phosphates: Dimeric, Tetrameric, and Polymeric Tin Phosphate ComplexesEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 9 2008Ramaswamy Murugavel Abstract Monoaryl phosphates with a bulky aryl substituent have been used to synthesize new organotin clusters and polymers. The equimolar reaction between 2,6-diisopropylphenylphosphate (dipp-H2) and Me2SnCl2 in ethanol at 25 °C leads to the formation of [Me2Sn(,3 -dipp)]n (1), while the reaction of 2,6-dimethylphenylphosphate (dmpp-H2) with Me2SnCl2 in either a 1:1 or 2:1 molar ratio proceeds to produce exclusively [Me2Sn(,-dmpp-H)2]n·nH2O (2). Compounds 1 and 2 are 1D polymers with different architectures. In compound 1, the tin atom is five-coordinate (trigonal bipyramidal). Each dipp ligand bridges three different tin atoms to form an infinite ladder-chain structure. In 2, each six-coordinate (octahedral) tin atom is surrounded by four phosphate oxygen atoms originating from four different bridging dmpp-H ligands, thus forming a spirocyclic coordination polymeric chain. The use of nBu2SnO as the diorganotin source in its reaction with dipp-H2 leads to the isolation of dimeric [nBu2Sn(,-dipp-H)(dipp-H)]2 (4), which contains a central Sn2O4P2 unit. There are two chemically different half molecules of 4 in the asymmetric part of the unit cell and hence it actually exists as a 1:1 mixture of [nBu2Sn(,-dipp-H)(dipp-H)]2 and [nBu2Sn(,-dipp)(dipp-H2)]2 in the solid state. The reaction of the monoorgano tin precursor nBuSn(O)(OH)·xH2O with dipp-H2 takes place in acetone at room temperature to yield the tetrameric cluster 5, which has different structures in the solution and in the solid state. 31P NMR spectroscopy clearly suggests that 5 has the formula [nBu4Sn4(,-O)2(,-dipp-H)8] in solution. The single-crystal X-ray diffraction studies in the solid state, however, reveal that compound 5 exists as [nBu4Sn4(,-OH)2(,-dipp-H)6(,-dipp)2]. The use of compounds 1,4 as possible precursors for the preparation of ceramic tin phosphate materials has been investigated. The thermolysis of 1 at 500 °C leads to the formation of quantitative amounts of Sn2P2O7, while the thermolysis of 2, 3, and 4 under similar conditions results in the formation of SnP2O7. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source] Preparation of Fused Tetracyclic Quinazolinones by Combinations of Aza-Wittig Methodologies and CuI -Catalysed Heteroarylation ProcessesEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 15 2009Juan Antonio Bleda Abstract A number of linear quinazolinones fused to five-membered rings , benzimidazo[2,1- b]quinazolinones 8 and benzothiazolo[2,3- b]quinazolinones 10 , have been prepared from iminophosphoranes 4, derived from N -substituted o -azidobenzamides by a combination of the aza-Wittig methodology and CuI -catalysed heteroarylation. The presence of a nitrogen functionality in the N -aryl substituent of 4 promotes heterocyclization after an aza-Wittig reaction/reductive process, either across the 2-position, to afford quinazolino[2,1- b]quinazolinones 11,14, or across the 4-position, to afford the benzimidazo[1,2- c]quinazoline 16 from the initially formed 3H -quinazolin-4-one. When an acetyl group is present in the N -aryl substituent of 4, aza-Wittig reactions with isocyanates lead directly to 4-methylene-4H -3,1-benzoxazines 18; this transformation involves the initial formation of a carbodiimide, which undergoes ring-closure through the enol form of the carboxamide group and eventually an unprecedented iminobenzoxazine/methylenebenzoxazine rearrangement. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source] Enders' SAMP-Hydrazone as Traceless Auxiliary in the Asymmetric 1,4-Addition of Cuprates to EnonesADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 13 2010Karsten Sammet Abstract Conjugate additions of Gilman cyanocuprates to (S)- N -amino-2-(methoxymethyl)pyrrolidine (SAMP)-hydrazones 4, 5 derived from cyclic and acyclic ,,,-unsaturated ketones were investigated. A protocol utilizing copper(II) sulfate/ammonium chloride was evolved, which allowed cleavage of SAMP (S)- 1 under the hydrolysis and work-up conditions, followed by recovery of the auxiliary with ethylenediaminetetraacetic acid (EDTA). The enantioselectivity of cuprate additions was dominated for cyclic SAMP-hydrazones 4 by the cuprate alkyl substituent and the ring size, in the case of acyclic arylidene SAMP-hydrazones 5, however, by the nature of the aryl substituent. Electron-donating substituents gave poor enantiomeric excesses, whereas electron-withdrawing groups provided excellent ee values of 98,99%. The configuration of the new stereocenter was determined to be (R). Moreover, a reaction sequence was developed which integrates a tandem 1,4-addition/methylation and traceless hydrolytic cleavage of the auxiliary (S)- 1 in a one-pot reaction, resulting in enantiomerically pure methyl ketones 11,13, each of them with>99% ee. [source] A paradigm for the mechanisms and products of spontaneous polymerizationsJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 24 2009H. K. Hall Jr. Abstract In spontaneous vinyl and ring-opening copolymerizations, polar and resonance effects on the intermediates from bond-forming initiation offer a continuous spectrum of reactivities and polymer structures. In bond-forming initiation, an electron-rich donor monomer forms a bond to an acceptor monomer. The donor monomer may be a vinyl monomer with O, N, or aryl substituent or it may be an aza- or oxacycle. The acceptor monomer may be a vinyl monomer carrying CN, COOR, or SO2R substituent or it may be a cyclic anhydride or maleimide. Beyond this, the donor may have a ,-like strained single bond, whereas the acceptor may be an electrophilic quinodimethane. Lewis acids may be used to enhance the electrophilicity of acceptor monomers. Reaction rates and polymer composition are determined by systematically varying the stability of the first intermediate, designated P (for polymethylene). The nature of the intermediate will vary from a highly reactive trans biradical, which initiates chain alternating copolymerization, to a cis/gauche zwitterion, which can initiate chain ionic homopolymerization, to an extremely stabilized zwitterion, which cannot add monomer, but builds up in concentration and terminates by combination, forming alternating copolymer. This model embraces the existing literature for a wide variety of monomers and possesses predictive power. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2009 [source] New Chiral N-Heterocyclic Carbene Ligands in Palladium-Catalyzed ,-Arylations of Amides: Conformational Locking through Allylic Strain as a Device for StereocontrolCHEMISTRY - A EUROPEAN JOURNAL, Issue 21 2010Yi-Xia Jia Dr. Abstract New Enders/Herrmann-type chiral N-heterocyclic carbene (NHC) ligands have been developed and applied in asymmetric palladium-catalyzed intramolecular ,-arylations of amides. The best ligands feature the bulky tert -butyl group and ortho -substituted aryl groups at the stereogenic centers. Aryl bromides readily react at room temperature and aryl chlorides at 50,°C. The highly enantiomerically enriched (up to 96,%,ee) 3-alkyl-3-aryloxindole products were obtained in generally high yields (>95,%) except in cases of steric congestion. The critical roles both of the bulky alkyl group and of the ortho -aryl substituent at the stereogenic center of the ligand were revealed in the crystal structure of a [Pd(,3 -allyl)(NHC-L*)(I)] complex. The ligand aryl location and orientation is fixed by conformational locking that minimizes A1,3 -strain and enables optimal transfer of chiral information. [source] Chiral discrimination of 2-arylalkanoic acids by (1S,2S)-1-aminoindan-2-ol and (1S,2S)-2-aminoindan-1-ol: Correlation of the relative configuration of the amino and hydroxy groups with the pattern of a supramolecular hydrogen-bond network in the less-soluble diastereomeric saltCHIRALITY, Issue 6 2003Kazushi Kinbara Abstract The diastereomeric resolution of 2-arylalkanoic acids with enantiopure trans -1-aminoindan-2-ol and trans -2-aminoindan-1-ol were studied. Enantiopure trans -1-aminoindan-2-ol had a moderate resolving ability for 2-arylalkanoic acids having a naphthyl group as an aryl substituent at the ,-position, while enantiopure trans -2-aminoindan-1-ol had a moderate-to-high resolving ability for a wide variety of the acids having a methyl group as an alkyl substituent at the ,-position. The crystal structures of the corresponding less-soluble salts revealed that a reinforced columnar hydrogen-bond network was formed in the less-soluble salts with trans -1-aminoindan-2-ol, while a rather stable hydrogen-bond sheet was generated with the assistance of water molecules in the less-soluble salts with trans -2-aminoindan-1-ol. These results suggest that not only the relative configuration but also the position of the hydrogen-bonding groups in resolving agents have a considerable effect on the structure of the less-soluble salts. The difference in favorable hydrogen-bond structure determined the adaptivity to the structural feature of target racemic 2-arylalkanoic acids in the resolution by trans -1-aminoindan-2-ol and trans -1-aminoindan-2-ol, respectively. Chirality 15:564,570, 2003. © 2003 Wiley-Liss, Inc. [source] Iminohydroxamato Early and Late Transition Metal Halide Complexes , New Precatalysts for Aluminoxane-Cocatalyzed Olefin Insertion PolymerizationEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 8 2004Alexander Krajete Abstract We report on new families of non-metallocene metal precatalysts for olefin polymerization with titanium, zirconium, vanadium and nickel as the active metal sites. The novel ligand design concept is based on iminohydroxamic acids and their derivatives as the principal chelating units. Various anionic and neutral [N,O] and [N,N] ligand systems are easily accessible by a modular synthetic sequence of imidoyl chlorides with substituted hydroxylamines or hydrazines, respectively. Steric protection of the metal coordination site, a necessary requirement for suppression of chain termination pathways of non-metallocene catalysts, is brought about by bulky aryl substituents on the imino nitrogen atoms. Crystal structures of some of the hydroxamato ligands reveal interesting intermolecular hydrogen-bridged structures, whereas in the solid-state structure of one titanium precatalyst a five-membered chelate was observed, in line with the design principle of these systems. Preliminary ethylene polymerization studies with methylaluminoxane-activated metal complexes (M = Ti, Zr, V, Ni) show that the most active systems are [N,O]NiBr2 catalysts containing neutral O -alkyl iminohydroxamate ligands. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004) [source] Syntheses, Structures and Theoretical Investigations of 1,4,3,4,5,4 -Trithia-2,4,6,8,9-pentaazabicyclo[3.3.1]nona-1(9),2,3,5,7-pentaenesEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 17 2003Carsten Knapp Abstract The syntheses of the title compounds RCN5S3 with electron-withdrawing aryl substituents [R = 2-FC6H4 (1m), 4-FC6H4 (1n), 2,6-F2C6H3 (1o), C6F5 (1p), 4-NCC6H4 (1q) and Cl3C (1r)] are described. The X-ray structures of 1n, 1o, 1q and 1r, together with those of Me2NCN5S3 (1b) and 4-CH3C6H4CN5S3 (1f), are reported. The experimentally determined dependence of the bond lengths on the substituents R within the bicyclic system RCN5S3 is well-reflected in the results of the theoretical calculations (RHF, MP2, B3LYP). The bonding model developed shows that acceptor substituents do not influence bonding within the bicycle. In the solid state, two fundamentally different primary interactions of the RCN5S3 molecules are observed; "stacking" and "dimerisation", which can be rationalised by electrostatic interactions between the CN5S3 units. However, secondary effects , the interactions between the R substituents , may be even more dominant. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003) [source] 3,4-Dihydro-3H -pyrrol-2-imines as Conformationally Restrained 1,3-Diazabutadienes: Synthesis, Structural Properties and Protonation,EUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 13 2009Simon Janich Abstract 5-Aryl-3,3,4,4-tetramethyl-3,4-dihydro-3H -pyrrol-2-imines,conformationally restrained 1,3-diazabuta-1,3-diene derivatives, were easily prepared by treating aryllithium species with 2,2,3,3-tetramethylsuccinonitrile (1). Trapping the reaction intermediate with chlorotrimethylsilane gave N -silylated compounds 2a,e, whereas aqueous workup gave N-H derivatives 3a,b. Pyrenyl-substituted compound 3b was characterised by X-ray diffraction studies, revealing the presence of both intermolecular aromatic face-to-face contacts and the formation of homodimers by twofold H-bonding. N -Silylated derivatives 2a,d were used successfully as nucleophilic components in palladium-catalysed C,N bond-forming reactions to obtain N -arylated compounds 5b,h,j,k,m and 7a,d. The UV spectra of compounds 5 and 7 exhibit long wavelength absorptions up to 462 nm for 7d, thus indicating extended ,,,* conjugation. Dihydropyrrolimine-based compounds with larger conjugated aryl substituents in the 5-position react with Brønsted and Lewis acids displaying a significant colour change that could be used to estimate the pKb of 3a to a value of ,4.5. Derivatives 2c,e and 3a,b, which are not N -arylated, are fluorescent with a Stokes shift of 107 nm (6034 cm,1) for 3a. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source] An Efficient Approach for the Synthesis of N-1 Substituted HydantoinsEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 11 2008Vinod Kumar Abstract An efficient three-step route for the synthesis of N - 1 alkyl/aryl-substituted hydantoins was developed from inexpensive commercially available substrates. The reaction of amines with cyanogen bromide takes place to give monoalkyl/aryl cyanamides. This on treatment with methyl bromoacetate in the presence of sodium hydride in tetrahydrofuran affords methyl N -cyano- N -alkyl/arylaminoacetate, which undergoes hydrolysis and cyclization in the presence of 50,% H2SO4 to afford N - 1 substituted hydantoins in very good-to-excellent yields. Wide varieties of final products having primary, secondary, tertiary, and aryl substituents at the N - 1 position were successfully synthesized by this method. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source] Effects of Extended Aryl-Substituted Bisoxazoline Ligands in Asymmetric Synthesis , Efficient Synthesis and Application of 4,4,-Bis(1-Naphthyl)-, 4,4,-Bis(2-Naphthyl)- and 4,4,-Bis(9-Anthryl)-2,2,-isopropylidenebis(1,3-oxazolines)EUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 23 2005Hester L. van Lingen Abstract The steric influence of extended aryl substituents on 2,2,-bis(1,3-oxazoline) ligands was investigated in a series of asymmetric catalytic reactions such as Mukaiyama aldol and Michael reactions, hetero-Diels,Alder processes, and allylic alkylation reactions. 4,4,-(2-Naphthyl)- and 4,4,-(9-anthryl)-substituted isopropylidene-bridged 2,2,-bis(1,3-oxazolines) were synthesized and their enantioselective and catalytic properties in combination with different metals evaluated. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005) [source] Direct Amination of meso -Tetraarylporphyrin Derivatives , Easy Route to A3B-, A2BC-, and A2B2 -Type Porphyrins Bearing Two Nitrogen-Containing Substituents at the meso -Positioned Phenyl GroupsHELVETICA CHIMICA ACTA, Issue 10 2007Stanis, aw Ostrowski Abstract meso -Tetraarylporphyrinato complexes 1a,g (ZnII, CuII, and NiII) bearing one or two nitro-substituted aryl moieties react with 1,1,1-trimethylhydrazinium iodide in the presence of tBuOK in THF at 0,5° or in the presence of KOH in DMSO at 60,70° according to a nucleophilic substitution of an H-atom, thus affording porphyrins 2a,g and 3f,g with amino-functionalized meso -positioned aryl substituents in yields up to 73% (Scheme,1 and Table). The products obtained are attractive intermediates for further derivatization of porphyrins and may be of potential use as sensitizers in photodynamic cancer therapy. [source] Synthesis of Sulfoximines and Sulfilimines with Aryl and Pyrazolylmethyl SubstituentsADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 2-3 2010Olga García Mancheño Abstract Sulfoximines bearing pyrazolylmethyl and aryl substituents, which are relevant to the crop protection industry, and their corresponding sulfilimine intermediates, have been prepared from sulfide precursors by either iron-catalyzed nitrogen transfer reactions or metal-free imination procedures. Whereas the former approach leads to N -nosyl-substituted products, the latter affords N -cyano derivatives. [source] Chiral Phosphoric Acid-Catalyzed Enantioselective Aza-Friedel,Crafts Reaction of IndolesADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 11-12 2007Masahiro Terada Abstract A highly enantioselective 1,2-aza-Friedel,Crafts reaction of N - tert -butyldimethylsilylindole with N - tert -butoxycarbonyl aromatic imines is demonstrated using a BINOL-derived monophosphoric acid catalyst. The present approach provides efficient access to 3-indolylmethaneamines with aryl substituents in excellent enantioselectivities (up to 98,% ee). An inversion in the sense of enantioselection was found between monophosphoric acid catalysts bearing different substituents introduced at the 3,3,-position of binaphthyl backbone. We also calculated the three-dimensional structure of the monophosphoric acid catalysts to speculate on the inversion of the stereochemical outcome. [source] Structural, electronic, and optical properties of 9-heterofluorenes: A quantum chemical studyJOURNAL OF COMPUTATIONAL CHEMISTRY, Issue 13 2007Run-Feng Chen Abstract Density-functional theory studies were applied to investigate the structural, electronic, and optical properties of 9-heterofluorenes achieved by substituting the carbon at 9 position of fluorene with silicon, germanium, nitrogen, phosphor, oxygen, sulfur, selenium, or boron. These heterofluorenes and their oligomers up to pentamers are highly aromatic and electrooptically active. The alkyl and aryl substituents of the heteroatom have limited influence, but the oxidation of the atom has significant influence on their molecular structures and properties. The highest occupied molecular orbital (HOMO)-lowest occupied molecular orbital (LUMO) interaction theory was successfully applied to analyze the energy levels and the frontier wave functions of these heterofluorenes. Most heterofluorenes belong to type B of interaction with low-lying LUMO and have the second kind of wave function. Carbazole and selenafluorene have type C of interaction with high-lying HOMO and the third kind of wave function. Types C and D of heterofluorenes, such as carbazole, oxygafluorene, sulfurafluorene, and selenafluorene also have high triplet state energies. The extrapolated HOMO and LUMO for polyheterofluorenes indicate that polyselenonafluorene has the lowest LUMO; polycarbazole has the highest HOMO; polyselenafluorene has the highest bandgap (Eg); and polyborafluorene has the lowest Eg. Heterofluorenes and their oligomers and polymers are of great experimental interests, especially those having extraordinary properties revealed in this study. © 2007 Wiley Periodicals, Inc. J Comput Chem, 2007 [source] The reaction of aryl and heteroarylhydrazines with aryl-trifluoromethyl ,-diketonesJOURNAL OF HETEROCYCLIC CHEMISTRY, Issue 4 2006Shiv P. Singh We report the results obtained when five aromatic or heteroaromatic hydrazines react with six ,-diketones bearing trifluoromethyl and aryl substituents. Forty-two compounds have been isolated corresponding to two isomeric trifluoromethyl pyrazoles and the intermediate 5-CF3, 5-OH pyrazolines. The results have provided useful information for establishing the mechanism of the synthesis of pyrazoles. [source] New calcineurin inhibiting 3-dimethylaminopropyl substituted diarylheterocycles by sonogashira reactions and catalytic hydrogenationJOURNAL OF HETEROCYCLIC CHEMISTRY, Issue 7 2005Lunxiang Yin A series of calcineurin inhibiting compounds 1 consisting of a central aromatic N-heterocycle, two aryl substituents and a 3-dimethylaminopropyl chain was synthesized by introduction of the side chain. A corresponding haloheterocycle 3 was transformed into a 3-dimethylaminopropynylheterocycle 2 by Sonogashira coupling and was in turn hydrogenated in the presence of Pd/C to afford the 3-dimethylaminopropyl-sub-stiuted heterocycles 1. Some of the products showed calcineurin inhibiting activity. [source] 3,3,4,4,5,5-Hexafluoro-1-(2-methoxyphenyl)-2-[5-(4-methoxyphenyl)-2-methyl-3-thienyl]cyclopent-1-ene: a photochromic compoundACTA CRYSTALLOGRAPHICA SECTION C, Issue 5 2009Congbin Fan The photochromic title compound, C24H18F6O2S, has thienyl and aryl substituents on the C=C double bond of the shallow half-chair-shaped cyclopentene ring. The planes of the two substituent rings are inclined to that of the cyclopentene ring, with dihedral angles between the mean plane of the cyclopentene ring and those of the phenylene and thienyl rings of 51.2,(1) and 51.3,(1)°, respectively. The molecule adopts an antiparallel conformation, with a distance between the two photoreactive C atoms of 3.717,(2),Å. [source] Conformational Control of [26]Hexaphyrins(1.1.1.1.1.1) by meso -Thienyl SubstituentsCHEMISTRY - A EUROPEAN JOURNAL, Issue 1 2007Masaaki Suzuki Abstract Conformational preference and chemical stability of meso -aryl-substituted [26]hexaphyrins(1.1.1.1.1.1) ([26]ArH) depend upon meso -aryl substituents. Although only a planar and rectangular conformation (type-II conformation) has been identified for [26]ArH so far, we have demonstrated here that a different conformation with all the pyrroles pointing inward (type-I conformation) is preferred for [26]ArH (7 and 11 -I) bearing small 2-thienyl or 3-thineyl substituents at 15- and 30-positions. Both type-I and type-II [26]ArH exhibit diatropic ring currents, reflecting aromatic character. Type-I [26]ArH, such as 7 and 11 -I, have been shown to serve as an effective ligand for PdII ions to provide bis-PdII complexes 12 and 13 with N3C1 coordination through facile CH bond activation. [source] From Dioxin to Drug Lead,The Development of 2,3,7,8-TetrachlorophenothiazineCHEMMEDCHEM, Issue 6 2007Kristian Abstract Polychlorinated dibenzo-p-dioxins are persistent environmental pollutants. The most potent congener, 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), causes a wasting syndrome and is a potent carcinogen and immunosuppressant in the rat at high doses. However, low doses cause opposite effects to some of those observed at higher doses, resulting in chemoprevention, stimulation of the immune system, and longevity in experimental animals. The new TCDD analogue, 2,3,7,8-tetrachlorophenothiazine (TCPT), was developed to take advantage of the low-dose effects of dioxins that have potential application as therapeutics. Its development marked a deviation from the traditional scope of phenothiazine drug design by deriving biological effects from aryl substituents. TCPT was synthesized in three steps. The key ring-closing step was performed utilizing a Buchwald-Hartwig amination to provide TCPT in 37,% yield. Its potency to induce CYP1A1 activity over 24,h was 370 times lower than that of TCDD in,vitro. The elimination half-life of the parent compound in serum was 5.4,h in the rat and 2.7,h in the guinea pig, compared to 11 and 30 days, respectively, for TCDD. These initial findings clearly differentiate TCPT from TCDD and provide the basis for further studies of its potential as a drug lead. [source] | ||||||||||||||||||||||