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Allyl
Terms modified by Allyl Selected AbstractsPyrazole-Bridged NHC Ligands and Their Dimetallic (Allyl)palladium ComplexesEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 3 2008Ulrich J. Scheele Abstract A set of compartmental pyrazole-based ligands with appended NHC donors has been synthesized and isolated as [H4L]Cl3 and [H3L](PF6)2 salts. Dinuclear (allyl)palladium complexes of these ligands are conveniently accessible via the in situ prepared silver species. Three complexes [(allyl)2Pd2L]PF6 and one derivative [(methallyl)2Pd2L]PF6 have been characterized crystallographically, which revealed that the metal ions are positioned in close proximity [d(Pd···Pd) = 3.97,4.05 Å], with two possible mutual orientations of the (meth)allyl ligands within the dimetallic pocket. NMR spectroscopy shows slow interconversion of these isomers (k = 0.05,0.4 s,1), where the (meth)allyl ligands are detached trans to the carbene during this ,3 -,1 -,3 dynamic process.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source] BEHAVIOR OF AVIRULENT YERSINIA PESTIS IN LIQUID WHOLE EGG AS AFFECTED BY STORAGE TEMPERATURE, ANTIMICROBIALS AND THERMAL PASTEURIZATIONJOURNAL OF FOOD SAFETY, Issue 3 2010JOSHUA B. GURTLER ABSTRACT Yersinia spp. are psychrotrophic bacteria capable of growth at temperatures as low as ,2C, known to contaminate shell eggs and liquid eggs in the U.S.A. and South America. A study was performed to determine the thermal sensitivity of avirulent Yersinia pestis in liquid whole egg (LWE), evaluate the growth pattern of the bacterium in LWE at temperatures of 4,22C and assess the ability of 10 antimicrobial compounds to inhibit the growth of attenuated Y. pestis in LWE. The estimated decimal reduction values of avirulent Y. pestis in LWE at 54C (D54) were 1.39,1.58 min, and D60 values were 13.8 and 11.4 s by the addition of 0 and 965 IU of nisin (MP Biomedicals, LLC, Solon, OH), respectively. Low molecular weight chitosan (0.5%) and an activated lactoperoxidase system (2.18 U/mL) were ineffective at inhibiting growth of Y. pestis, while 500 IU/mL of nisin inhibited populations by up to 1 log cfu/mL at 4, 10 and 15C when compared with the control. Allyl isothiocyanate, diacetyl, diethyl dicarbonate, ethylenediaminetetraacetic acid, methylparaben, monolaurin and benzoyl peroxide inhibited the growth of attenuated Y. pestis when added at high levels. PRACTICAL APPLICATIONS The genus Yersinia does not currently pose a problem in pasteurized liquid egg products, although it has been isolated from eggs in the U.S.A. and Argentina. Yersiniae, which are psychrotrophic bacteria, can grow at temperatures as low as ,2C; therefore, incidental or intentional contamination of liquid whole egg (LWE) with Yersinia spp. could result in multiplication to high populations, even when stored under refrigeration (ca. 4C). We have shown that avirulent Yersinia pestis is able to multiply to populations of >2, 5 and 8 log cfu/mL in LWE at 4C within 6, 14 and 26 days, respectively. This study provides information that will be helpful in determining thermal and nonthermal means of controlling yersiniae in LWE products. [source] Allyl isothiocyanate as a cancer chemopreventive phytochemicalMOLECULAR NUTRITION & FOOD RESEARCH (FORMERLY NAHRUNG/FOOD), Issue 1 2010Yuesheng Zhang Abstract Allyl isothiocyanate (AITC), which occurs in many common cruciferous vegetables, is widely and often frequently consumed by humans. Besides antimicrobial activity against a wide spectrum of pathogens, it showed anticancer activity in both cultured cancer cells and animal models, although the underlining mechanisms remain largely undefined. Bioavailability of AITC is extremely high, as nearly 90% of orally administered AITC is absorbed. AITC absorbed in vivo is metabolized mainly through the mercapturic acid pathway and excreted in urine. Available data suggest that urinary concentrations of AITC equivalent are at least ten times higher than in the plasma, and tissue levels of AITC equivalent in the urinary bladder were 14,79 times higher than in other organs after oral AITC administration to rats. These findings suggest that AITC may be most effective in the bladder as a cancer chemopreventive compound. AITC at high-dose levels also exhibit a low degree of cytotoxicity and genotoxicity in animal studies, but such adverse effects are unlikely in humans exposed to dietary levels of AITC. Overall, AITC exhibits many desirable attributes of a cancer chemopreventive agent, and further studies are warranted in order to elucidate its mechanism of action and to assess its protective activity in humans. [source] S -Allyl- L -Cysteine Sulfoxide Inhibits Tumor Necrosis Factor-Alpha Induced Monocyte Adhesion and Intercellular Cell Adhesion Molecule-1 Expression in Human Umbilical Vein Endothelial CellsTHE ANATOMICAL RECORD : ADVANCES IN INTEGRATIVE ANATOMY AND EVOLUTIONARY BIOLOGY, Issue 3 2010Chai Hui Abstract Garlic and its water-soluble allyl sulfur-containing compound, S -Allyl- L -cysteine Sulfoxide (ACSO), have shown antioxidant and anti-inflammatory activities, inhibiting the development of atherosclerosis. However, little is known about the mechanism(s) underlying the therapeutic effect of ACSO in inhibiting the formation of atherosclerostic lesion. This study aimed to investigate whether ACSO could modulate tumor necrosis factor-alpha (TNF-,)-induced expression of intercellular cell adhesion molecule-1, monocyte adhesion and TNF-,-mediated signaling in human umbilical vein endothelial cells. While TNF-, promoted the intercellular cell adhesion molecule-1 mRNA transcription in a dose- and time-dependent manner, ACSO treatment significantly reduced the levels of TNF-,-induced intercellular cell adhesion molecule-1 mRNA transcripts (P < 0.01). Furthermore, ACSO dramatically inhibited TNF-, triggered adhesion of THP-1 monocytes to endothelial cells and porcine coronary artery rings. Moreover, ACSO mitigated TNF-, induced depolarization of mitochondrial membrane potential and overproduction of superoxide anion, associated with the inhibition of NOX4, a subunit of nicotinamide adenine dinucleotide phosphate-oxidase, mRNA transcription. In addition, ACSO also inhibited TNF-,-induced phosphorylation of JNK, ERK1/2 and I,B, but not p38. Apparently, ACSO inhibited proinflammatory cytokine-induced adhesion of monocytes to endothelial cells by inhibiting the mitogen-activated protein kinase signaling and related intercellular cell adhesion molecule-1 expression, maintaining mitochondrial membrane potential, and suppressing the overproduction of superoxide anion in endothelial cells. Therefore, our findings may provide new insights into ACSO on controlling TNF-,-mediated inflammation and vascular disease. Anat Rec, 2010. © 2010 Wiley-Liss, Inc. [source] Rhodium(II)-Catalyzed One-Pot Four-Component Synthesis of Functionalized Polyether Macrocycles at High Concentration,ANGEWANDTE CHEMIE, Issue 40 2010Dr. Walid Zeghida Vollkommen unerwartet wurde die Rhodium(II)-katalysierte templatfreie Makrocyclisierung von vier Einzelkomponenten in einem Reaktionsgefäß effizienter, wenn die Konzentration erhöht wurde. Daher kondensierten ,-Diazo-,-ketoester mit 1,4-Dioxan, THF oder Tetrahydropyran als Lösungsmittel zu 16- bis 18-gliedrigen Polyethermakrocyclen in bis zu 75,% Ausbeute (siehe Schema; R=Me, Et, PhCH2CH2, Allyl, PhCHCH2). [source] Unerwartete nucleophile Umlagerung von Amiden: ein stereoselektiver Zugang zu anspruchsvoll substituierten Lactonen,ANGEWANDTE CHEMIE, Issue 9 2010Claire Madelaine Dr. Überraschung! Eine unerwartete Umlagerung führt chemo- und stereoselektiv zu ,-Allyl- und Allenyl-Lactonen mit anspruchsvollem Substitutionsmuster (siehe Schema). Die universelle Anwendbarkeit dieser Reaktion, ihre einzigartigen Eigenschaften und ihr Potenzial für Synthesen sind ebenso beschrieben wie erste mechanistische Betrachtungen. [source] ChemInform Abstract: Copper-Catalyzed ,-Selective Allyl,Alkyl Coupling Between Allylic Phosphates and Alkylboranes.CHEMINFORM, Issue 31 2010Hirohisa Ohmiya 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] ChemInform Abstract: One-Pot Amide Synthesis from Allyl or Benzyl Halides and Amines by Pd-Catalyzed Carbonylation.CHEMINFORM, Issue 14 2010Luigino Troisi 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] ChemInform Abstract: Highly Diastereo- and Enantioselective Pd-Catalyzed Cyclopropanation of Acyclic Amides with Substituted Allyl Carbonates.CHEMINFORM, Issue 48 2009Wei Liu 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: Silylated Azolium Salts and Their Applications in the Synthesis of Azolines and ,-Enaminoketones Bearing Allyl-, Vinyl-, and Acylsilane or ,-Silylketone Units.CHEMINFORM, Issue 44 2009Ana M. Gonzalez-Nogal 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 of Prenylarenes and Related (Multisubstituted Allyl)arenes from Aryl Halides and Homoallyl Alcohols via Palladium-Catalyzed Retro-Allylation.CHEMINFORM, Issue 23 2009Masayuki Iwasaki 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: Catalytic Enantioselective Allyl- and Crotylboration of Aldehydes Using Chiral Diol×SnCl4 Complexes.CHEMINFORM, Issue 45 2008Mechanistic Investigations., Optimization, Substrate Scope 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: Gold-Catalyzed Allyl,Allyl Coupling.CHEMINFORM, Issue 26 2008Susana Porcel 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: Remarkable Solvent Effect on Pd(0)-Catalyzed Deprotection of Allyl Ethers Using Barbituric Acid Derivatives: Application to Selective and Successive Removal of Allyl, Methallyl, and Prenyl Ethers.CHEMINFORM, Issue 18 2008Hirokazu Tsukamoto 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] Catalytic Enantioselective and Catalyst-Controlled Diastereofacial-Selective Additions of Allyl- and Crotylboronates to Aldehydes Using Chiral Broensted Acids.CHEMINFORM, Issue 32 2006Vivek Rauniyar 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] Modified (NHC)Pd(Allyl)Cl (NHC = N-Heterocylic Carbene) Complexes for Room-Temperature Suzuki,Miyaura and Buchwald,Hartwig Reactions.CHEMINFORM, Issue 32 2006Nicolas Marion 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] Aluminum Chloride-Catalyzed Intramolecular Allyl-Migration Reaction of Allyl(chloromethyl)silanes and Trapping of the Intermediate with Allyltrimethylsilane.CHEMINFORM, Issue 7 2005Hoon Yi Jung Abstract For Abstract see ChemInform Abstract in Full Text. [source] Solvent-Free Amination Reactions of Aryl Bromides at Room Temperature Catalyzed by a (,-Allyl)palladium Complex Bearing a Diphosphinidenecyclobutene Ligand.CHEMINFORM, Issue 4 2005Anil S. Gajare Abstract For Abstract see ChemInform Abstract in Full Text. [source] A Mild Protocol for Allylation and Highly Diastereoselective syn or anti Crotylation of Aldehydes in Biphasic and Aqueous Media Utilizing Potassium Allyl- and Crotyltrifluoroborates.CHEMINFORM, Issue 12 2003Avinash N. Thadani Abstract For Abstract see ChemInform Abstract in Full Text. [source] A New Pd0,CuI Bimetallic Catalyst for the Synthesis of Indoles from Isocyanates and Allyl Carbonates.CHEMINFORM, Issue 1 2003Shin Kamijo Abstract For Abstract see ChemInform Abstract in Full Text. [source] ChemInform Abstract: A New Allylidene Phosphorane Reagent for the Efficient Conversion of Aldehydes to ,,,-Unsaturated Allyl ,-Ketoesters.CHEMINFORM, Issue 13 2001Daniel Chapdelaine 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] Reactions of Pendant Boryl Groups in Cp,Metal Complexes: Heterocyclic Ring Annelation in a CpIr SystemEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 14 2008Christoph Herrmann Abstract Treatment of (cod)IrCl dimer with Li(allyl)cyclopentadienide gave (C5H4,CH2,CH=CH2)Ir(cod) (11). At 100 °C, 11 isomerizes cleanly into its ring-conjugated (trans -CH3,CH=CH,C5H4)Ir(cod) isomer (13). Subsequent addition of HB(C6F5)2 results in the formation of a product (16) that contains an annelated five-membered borata heterocycle at the Cp ring. This is probably formed by means of a reaction sequence involving regioselective hydroboration, followed by an electrophilic substitution reaction at the Cp ring by the strongly Lewis acidic ,B(C6F5)2 group, in which the iridium metal base acts as the proton abstractor. Products 13 and 16 were characterized by X-ray diffraction. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source] Pyrazole-Bridged NHC Ligands and Their Dimetallic (Allyl)palladium ComplexesEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 3 2008Ulrich J. Scheele Abstract A set of compartmental pyrazole-based ligands with appended NHC donors has been synthesized and isolated as [H4L]Cl3 and [H3L](PF6)2 salts. Dinuclear (allyl)palladium complexes of these ligands are conveniently accessible via the in situ prepared silver species. Three complexes [(allyl)2Pd2L]PF6 and one derivative [(methallyl)2Pd2L]PF6 have been characterized crystallographically, which revealed that the metal ions are positioned in close proximity [d(Pd···Pd) = 3.97,4.05 Å], with two possible mutual orientations of the (meth)allyl ligands within the dimetallic pocket. NMR spectroscopy shows slow interconversion of these isomers (k = 0.05,0.4 s,1), where the (meth)allyl ligands are detached trans to the carbene during this ,3 -,1 -,3 dynamic process.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source] Synthesis and Transition Metal Complexes of Novel N,N,O Scorpionate Ligands Suitable for Solid Phase ImmobilisationEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 24 2006Eike Hübner Abstract Introduction of an allyl or a hydroxymethyl group to bis(3,5-dimethylpyrazol-1-yl)acetic acid (1) at the bridging carbon atom leads to the new tripodal N,N,O ligands 2,2-bis(3,5-dimethylpyrazol-1-yl)pent-4-enoic acid (Hbdmpzpen) (2) and 2,2-bis(3,5-dimethylpyrazol-1-yl)-3-hydroxypropionic acid (Hbdmpzhp) (3). These ligands exhibit similar chemical behaviour to that of 1, but they have the additional possibility to be immobilised to a solid phase. Esterification of the hydroxymethyl linker of 3 yields 2,2-bis(3,5-dimethylpyrazol-1-yl)-3-acetatopropionic acid (Hbdmpzap) (4). The molecular structures of 2, 3 and 4 all exhibit intramolecular hydrogen bridges. Introduction of a hydroxymethyl group to methyl bis(3,5-dimethylpyrazol-1-yl)acetate (5) yields methyl2,2-bis(3,5-dimethylpyrazol-1-yl)-3-hydroxypropionate(Mebdmpzhp) (6), which can be immobilised on Merrifield polymer to yield modified resin P - 6. To investigate the reactivity of these new ligands, manganese and rhenium complexes of 2, 3 and 4 have been studied. The molecular structures of the two manganese complexes [Mn(bdmpzpen)(CO)3] (7) and [Mn(bdmpzap)(CO)3] (8) have been confirmed by single-crystal X-ray structure determination. Saponification of polymer resin P - 6 and subsequent reaction with [ReBr(CO)5] yields rhenium tricarbonyl complexes anchored on Merrifield polymer (P -Re). Solid phase immobilisation of the [Mn(bdmpzpen)(CO)3] (7) and [Re(bdmpzpen)(CO)3] (9) complexes on 3-mercaptopropyl functionalised silica is initialised by AIBN. The tripodal coordination of manganese and rhenium in these functionalised Merrifield resins (P -Re) and silica (S -Mn, S -Re) is proven by a single A1 and two E signals in the IR spectra that are typical for unsymmetrical "piano stool" type carbonyl complexes. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006) [source] Mono- and Dimetallic Cyano Complexes with {Mo(,3 -allyl)(CO)2(N,N)} FragmentsEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 6 2003Julio Pérez Abstract Treatment of [MoCl(,3 -allyl)(CO)2(phen)] with NaCN in CH2Cl2/MeOH afforded [Mo(CN)(,3 -allyl)(CO)2(phen)] [allyl = C3H5 (1a); 2-MeC3H4 (1b)] as the sole products (no products of cyanide attack on the allyl group were detected). Treatment of 1a,b with [Mo(OTf)(,3 -C3H5)(CO)2(phen)] and NaBAr,4 in CH2Cl2 yielded the compounds [{Mo(,3allyl)(CO)2(phen)}(,-CN){Mo(,3 -C3H5)(CO)2(phen)}]BAr,4 (2a,b). Analogous treatment of 1a with fac -[M(OTf)(CO)3(bipy)] (M = Mn, Re) and NaBAr,4 resulted in the synthesis of [{Mo(,3 -C3H5)(CO)2(phen)}(,-CN){M(CO)3(bipy)}]BAr,4 (3, 4), in which the C and N atoms of the cyano bridge are bonded to Mo and M (M = Mn, Re), respectively. The linkage isomer of 4 (C and N atoms of the cyano group bonded to Re and Mo, respectively) (6) was prepared by treatment of [Re(CN)(CO)3(bipy)] (5) with [Mo(OTf)(,3 -C3H5)(CO)2(phen)] and NaBAr,4. Compounds 1a, 2b, 3, and 6 were characterized by X-ray diffraction. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003) [source] Cyclization of Trichloroacetimidates by Olefin Aminopalladation ,-Heteroatom EliminationEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 36 2009Ansis Maleckis Abstract The cyclization of ,-acetoxy- O -allyl- and ,-acetoxy- O -homoallyl-trichloroacetimidates to 4-vinyloxazolines and a 4-vinyldihydrooxazine has been efficiently achieved by olefin aminopalladation,,-heteroatom elimination. (Z)-Allylic imidates bearing a secondary ,-acetoxy group underwent PdII -catalysed cyclization to give the E isomers of 4-vinyloxazolines selectively and gave no Overman rearrangement products. Using a chiral substrate, it has been demonstrated that cyclization to 4-vinyloxazolines occurs with high chirality transfer. Stereoselective E isomer formation and chirality transfer provided a basis from which to discuss the possible reaction mechanism. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source] Enantioselective CpRu-Catalyzed Carroll Rearrangement , Ligand and Metal Source ImportanceEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 34 2008David Linder Abstract The addition of unstabilized carbonyl nucleophiles to unsymmetrical allyl-metal fragments still represents a challenge to generate stereogenic centers enantio- and regioselectively. In this context, the decarboxylative Carroll rearrangement of allyl ,-keto esters is particularly interesting, since chiral ,,,-unsaturated ketones are obtained. Herein, we show that CpRu half-sandwich complexes can, with selected enantiopure pyridine-monooxazoline ligands, catalyze this transformation and afford complete conversions along with good levels of regioselectivity and enantioselectivity. Even more challenging (electron-poor) substrates react (up to 86,% ee, branched/linear ratio , 97:03). In addition, the use of an air-stable metal precursor, namely [CpRu(,6 -naphthalene)][PF6], allows the reaction to be carried out reproducibly evenin non-anhydrous THF with a catalyst loading as low as2 mol-%. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source] Effect of the Leaving Group on the Rate and Mechanism of the Palladium-Catalyzed Isomerization of Cyclic Allylic Benzoates in Allylic SubstitutionsEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 5 2006Christian Amatore Abstract In chloroform, the reaction of cis -5-phenylcyclohex-2-enyl 4-Z-benzoate (cis - 1Z, Z = NO2, Cl, H, Me, MeO) with Pd0 complexes ligated to PPh3 is reversible and proceeds with isomerization at the allylic position. The rate of isomerization of cis - 1Z to trans - 1Z depends on the catalytic precursor: Pd0(PPh3)4 > {Pd0(dba)2 + 2PPh3} in agreement with an SN2 mechanism in the rate-determining isomerization of the cationic (,3 -allyl)palladium complexes formed in the oxidative addition. For a given precursor, the rate of isomerization of cis - 1Z to trans - 1Z also depends on the substituent Z, i.e., on the leaving group. The isomerization rate follows the same order as the leaving group properties: 4-NO2,C6H4 -CO2,> 4-Cl,C6H4 -CO2, > C6H5 -CO2, > 4-Me,C6H4 -CO2, > 4-MeO,C6H4 -CO2,. The same tendency is found for the equilibrium constant between the neutral cis - 1Z and the cationic (,3 -allyl)palladium complex in DMF. The higher the concentration of the cationic (,3 -allyl)palladium complex, the faster the isomerization of cis - 1Z to trans - 1Z is. The isomerization of cis - 1Z to trans - 1Z and that of the cationic (,3 -allyl)palladium complexes are at the origin of the lack of stereospecificity observed in catalytic nucleophilic allylic substitutions. These isomerizations are affected by both the leaving groups and the Pd0 precursors, which therefore are not "innocent" but may play an important role in palladium-catalyzed nucleophilic substitutions. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005) [source] Efficient Routes to Acenaphthylene-Fused Polycyclic Arenes/Heteroarenes and Heterocyclic Fluoranthene AnaloguesEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 10 2005Kausik Panda Abstract The acenaphthenone-derived , -oxoketene dithioacetal 2 has been subjected to various [3 + 3] aromatic and heteroaromatic annulation and other heterocyclization reactions previously developed in our laboratory, providing short and efficient routes to a diverse range of known and unknown acenaphtho-annulated linear and angular PAHs, heteroaromatics and five-membered heterocycles in good yields. Thus, benzo- and naphthoannulation of 2 with various allyl and benzyl Grignard reagents afforded substituted fluoranthenes 4a,c and benzo[k]fluoranthene 8, respectively, in good yields. Similarly, the parent benzo[j]fluoranthene 15a and its substituted derivative 16b have been synthesized by base-induced conjugate 1,4-addition of arylacetonitriles to 2, followed by acid-induced cyclization of the conjugate adducts 12a,b to give 13a,b and subsequent further transformations. The adducts obtained by 1,4-addition of anions derived from acetophenone and acenaphthenone were subjected toheterocyclization in the presence of ammonium acetate to give 8-arylacenaphtho[1,2- b]pyridines 18a,b and bis(acenaphtho)-annulated pyridine 20. Heterocyclization of 2 with bifunctional nucleophiles such as 2-picolyllithium and guanidinium nitrate afforded the corresponding acenaphtho[1,2- b]quinolizinium salt 23 and acenaphtho[1,2- d]pyrimidine 24, respectively, in high yields. Finally, acenaphtho[1,2- c]-fused five-membered heterocycles such as 7-(methylthio)acenaphtho[1,2- c]thiophene (25), 7-(methylthio)acenaphtho[1,2- c]furan (27) and 7-(methylthio)acenaphtho[1,2- c]pyrrole-2-carboxylic acid (30) were obtained in good yields by subjection of 2 to Simmons,Smith reaction conditions or by treatment with dimethylsulfonium methylide or glycinate dianion. Some of these newly synthesized PAHs or fused heterocycles were subjected to Raney Ni desulfurization to furnish sulfur-free compounds. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005) [source] Unusual Rearrangements of cis -4,7-Disubstituted 4,7-Dihydro4,7-dihydroxy[2.2]paracyclophanes on Dehydration: Stereoselective Formation of Planar Chiral CyclohexadienonesEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 4 2003Natalia Vorontsova Abstract Under acid conditions, cis -4,7-disubstituted 4,7-dihydro-4,7-dihydroxy[2.2]paracyclophanes undergo dehydration accompanied by rearrangement, affording cyclohexadienone derivatives as major products and with polysubstituted phenols being formed as minor products. The formation of either an ortho or a para semiquinoid system, as well as the configuration of the newly formed asymmetric center, depended strictly on the nature of the substituent (alkyl, allyl, or phenyl). The structures of 3,4-dihydro-3,7-dimethyl[2.2]paracyclophane-4-one (10), 3,7-diallyl-3,4-dihydro[2.2]paracyclophane-4-one (12), and 4,7-dihydro-7,8-diphenyl[2.2]paracyclophane-4-one (22) were determined by X-ray structural analysis. [2.2]Paracyclophane-4,7-quinone (1) was obtained in optically active form. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003) [source] | ||||||||||||||||||||||||||||||||||