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Palladium Catalysis (palladium + catalysis)
Selected AbstractsAtom-Efficient Vinylic Arylations with Triarylbismuths as Substoichiometric Multicoupling Reagents under Palladium CatalysisEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 25 2009Maddali L. N. Rao Abstract The first atom-efficient arylation of vinylic iodides was achieved by using triarylbismuths as substoichiometric multicoupling reagents under palladium catalysis. Vinylic iodides were efficiently coupled with electronically divergent triarylbismuths to furnish the corresponding arylated products in short reaction times. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source] The Newman,Kwart Rearrangement of O -Aryl Thiocarbamates: Substantial Reduction in Reaction Temperatures through Palladium Catalysis,ANGEWANDTE CHEMIE, Issue 41 2009Jeremy Viel ,cooler": Dank der Entwicklung eines Katalysators für die Newman-Kwart-Umlagerung lassen sich die harschen thermischen Bedingungen der unkatalysierten Reaktion nun vermeiden (siehe Schema). Ersten mechanistischen Studien zufolge (Isotopenmarkierung (2H, 18O, 34S), kinetische Messungen und DFT-Rechnungen) verläuft die Reaktion über eine oxidative Fünf-Zentren-Addition zu einem Pd-S-Komplex mit intermolekularem Austausch von Aryl- und Thiocarbamat-Gruppen durch Dimerisierung des Ruhekomplexes. [source] Regioselective Carbon,Carbon Bond Formation in Proteins with Palladium Catalysis; New Protein Chemistry by Organometallic ChemistryCHEMBIOCHEM, Issue 1 2006Koichiro Kodama Abstract Palladium-catalyzed reactions have contributed to the advancement of many areas of organic chemistry, in particular, the synthesis of organic compounds such as natural products and polymeric materials. In this study, we have used a Mizoroki,Heck reaction for site-specific carbon,carbon bond formation in the Ras protein. This was performed by the following two steps: 1) the His6 -fused Ras protein containing 4-iodo- L -phenylalanine at position 32 (iF32-Ras-His) was prepared by genetic engineering and 2) the aryl iodide group on the iF32-Ras-His was coupled with vinylated biotin in the presence of a palladium catalyst. The biotinylation was confirmed by Western blotting and liquid chromatography,mass spectrometry (LC-MS). The regioselectivity of the Mizoroki,Heck reaction was furthermore confirmed by LC-MS/MS analysis. However, in addition to the biotinylated product (bF32-Ras-His), a dehalogenated product (F32-Ras-His) was detected by LC-MS/MS. This dehalogenation resulted from the undesired termination of the Mizoroki,Heck reaction due to steric and electrostatic hindrance around residue 32. The biotinylated Ras showed binding activity for the Ras-binding domain as its downstream target, Raf-1, with no sign of decomposition. This study is the first report of an application of organometallic chemistry in protein chemistry. [source] ChemInform Abstract: Hydrodehalogenation of Halogenated Pyridines and Quinolines by Sodium Borohydride/N,N,N,,N,-Tetramethylethylenediamine under Palladium Catalysis.CHEMINFORM, Issue 27 2010Giorgio Chelucci 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: Synthesis of Alkylated Benzo[2,1-b:3,4-b,]dithiophenes (III) by Annulative Coupling and Their Direct Arylation under Palladium Catalysis.CHEMINFORM, Issue 13 2008Hiroyuki Watanabe 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: Site-Selective Modification of Peptides Using Rhodium and Palladium Catalysis: Complementary Electrophilic and Nucleophilic Arylation.CHEMINFORM, Issue 7 2008Christopher J. Chapman 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] Room Temperature Dehalogenation of Chloroarenes by Polymethylhydrosiloxane (PMHS) under Palladium Catalysis.CHEMINFORM, Issue 13 2003Ronald J. Rahaim Jr. Abstract For Abstract see ChemInform Abstract in Full Text. [source] Atom-Efficient Vinylic Arylations with Triarylbismuths as Substoichiometric Multicoupling Reagents under Palladium CatalysisEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 25 2009Maddali L. N. Rao Abstract The first atom-efficient arylation of vinylic iodides was achieved by using triarylbismuths as substoichiometric multicoupling reagents under palladium catalysis. Vinylic iodides were efficiently coupled with electronically divergent triarylbismuths to furnish the corresponding arylated products in short reaction times. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source] 4- exo - dig Cyclocarbopalladation: A Straightforward Synthesis of Cyclobutanediols from Acyclic ,-Bromopropargylic Diols under Microwave Irradiation Conditions,EUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 6 2006Christophe Bour Abstract Treatment of acyclic ,-bromopropargylic diols with tributylstannylated alkynes under palladium catalysis and microwave irradiation conditions gives high yields of the bis(alkylidene)cyclobutanediol derivatives and cyclobutenediols through an efficient 4- exo - dig cyclocarbopalladation. The cyclization is general with a wide variety of alkyne derivatives and gives access to new cyclobutane ring systems bearing one exocyclic double bond and one eneyne substituent as well as bicyclic dienes sharing a common double bond that may be of interest for further elaborations of complex molecules. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006) [source] Facile Construction of Spirocyclopropanated Bi-, Tri- and Tetracyclic Skeletons by Novel Cascades Involving Intra- and Intermolecular Heck Reactions of 2-Bromo-1,6-enynes and BicyclopropylideneEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 3 2005Michael Schelper Abstract Acyclic 2-bromo-1,6-enynes 5 -R, 9 -R and 11 -R with bulky substituents at the acetylenic terminus were co-cyclized with the highly strained bicyclopropylidene (12) under palladium catalysis at 80 °C to give the cross-conjugated tetraenes 13 -R, 18 -R and 19 -R in moderate-to-good yields (34,71%). Only the co-cyclization of 5 -Ph gave rise to an additional product, which was identified as the 11-membered ring 20. At elevated temperatures (120,140 °C) the initially formed tetraenes underwent 6,-electrocyclization to give spiro[cyclopropane-1,4,-bicylo[4.3.0]-1(6),2-dienes] 21 -R, 22 -R and 23 -R. This novel class of spirocyclopropanated oligocycles is also accessible by a one-pot protocol. The highest yields for both the tetraenes and bicyclo[4.3.0]nonadiene and its heteroanalogues were obtained with bulky substituents at the alkyne terminus of the precursors. Heteroatom-containing precursors 9 -R and 11 -R gave lower yields than their all-carbon analogues 5 -R. The acyclic 2-bromo-1,8-dien-6-ynes 28a,b,c upon palladium-catalyzed co-cyclization with bicyclopropylidene (12) at 110 °C gave spirocyclopropanated tricycles 31a,b and 32, respectively, in moderate yields (14, 31 and 32%). These products were formed by two consecutive 6,-electrocyclizations. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005) [source] Recyclable Heterogeneous Palladium Catalysts in Pure Water: Sustainable Developments in Suzuki, Heck, Sonogashira and Tsuji,Trost ReactionsADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 1 2010Marc Lamblin Abstract This review summarizes the progress made essentially these last ten years on heterogeneous palladium catalysis in pure water. The work covers four important palladium-catalyzed transformations for carbon-carbon bond formation: Suzuki, Heck, Sonogashira and Tsuji,Trost reactions. The discussion focuses on the efficiency and reusability of the heterogeneous catalysts as well as on the experimental conditions from a sustainable chemistry point of view. The review is introduced by a discussion on mechanistic aspects inherent to heterogeneous catalysis. [source] Direct Preparation of 7-Allyl- and 7-ArylindolinesADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 16 2009Daniele Leonori Abstract Addition of allyl halides to the organolithium species derived from lithiation of N - tert -butoxycarbonylindoline with sec -butyllithium (sec -BuLi) and tetramethylethylenediamine (TMEDA) occurs regioselectively by SN2 allylation. In contrast, the organolithium species can be transmetalated to the mixed zinc cuprate that undergoes regioselective SN2, allylations. Transmetalation to the organozinc chloride allows a Negishi-type cross-coupling reaction with aryl bromides using palladium catalysis with triphenylphosphine (PPh3) as ligand. The chemistry was applied to a very short synthesis of 7-prenylindole and of the alkaloid vasconine. [source] Gold Catalysis: Tandem Reactions of Diyne,Diols and External Nucleophiles as an Easy Access to Tricyclic Cage-Like Structures,CHEMISTRY - A EUROPEAN JOURNAL, Issue 32 2010Stephen Abstract Different diyne,diols composed of two terminal homopropargylic alcohol groups were prepared by bi-directional synthesis. Subjection of the syn diastereomers to NAC,gold catalysts (NAC=nitrogen acyclic carbene) in the presence of external nucleophiles such as water or anilines provided substituted and highly rigid heterocyclic cages. The corresponding anti disastereomers polymerised. An intermediate of the reactions of the syn diastereomers could be isolated and even be characterised by crystal structure analysis. Overall, eight new bonds are formed in the reaction, which proceeds by a multistep sequence of highly selective hydroalkoxylations and hydrohydroxylation or hydroaminations. For furyl substituents and for internal alkynes competing reaction pathways could be identified. By the cross-coupling of a product with an iodoaryl substituent, the use of these cage compounds as geometrically defined linking groups by using orthogonal transition-metal-catalysed methodology, namely, gold and palladium catalysis, could be demonstrated. [source] | ||||||||||||||||||||||