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Vinyl Bromides (vinyl + bromide)
Selected Abstracts1,3-Chirality Transfer by Fragmentation of Allylsulfinic Acids: A Diastereoselective Approach to Vinyl Bromides Related to trans -Hydrindane or trans -DecalinEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 15 2007Chochrek Abstract Diastereoselective approaches to vinyl bromides from bromoallylic alcohols by fragmentation of the respective allylsulfinic acids have been investigated. Bromoallylic alcohols 1a and 6 were transformed into the respective 1,3-benzothiazol-2-yl sulfides 2a and 7 by the Mitsunobu inversion reaction under modified conditions. The sulfides were then oxidized into sulfones 11a and 12a, respectively. Reduction of 11a and 12a with sodium borohydride gave the respective allylsulfinic acid salts 13a and 15 which, without isolation, were treated with aqeous tartaric acid. The salt 13a gave exclusively 5,-cholestane derivative 14a whereas 15 provided a mixture of the 5, and 5, derivatives 16 and 17 (after deprotection), the former prevailing. In an alternative approach, benzothiazolyl sulfides 2a and 7 were treated sequentially with BH3·THF and LiAlH4 to give thiols 18a and 19a, respectively. Oxidation of thiols 18a and 19a with oxaziridine 21 gave the respective sulfinic acids which, on gentle heating, afforded bromoolefins 14a and 22a, respectively, as the only products. Analogous reaction sequences starting from allylic alcohols devoid of the bromine substituent 1b and 8 have also been studied.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source] Iron-Catalyzed Cross-Coupling Reaction of Vinyl Bromides or Chlorides with Imidazoles in the Absence of Ligands and AdditivesADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 9 2009Jincheng Mao Abstract Highly effective coupling of imidazoles with (E)-vinyl halides can be achieved by using readily available iron catalysts under ligand-free, copper-free and palladium-free conditions. Coupling of (E)-vinyl bromides led to (Z)-products predominantly, while the reactions of (E)-vinyl chlorides afforded (E)-isomers as the major products. [source] ChemInform Abstract: Iron-Catalyzed Cross-Coupling Reaction of Vinyl Bromides or Chlorides with Imidazoles in the Absence of Ligands and Additives.CHEMINFORM, Issue 44 2009Jincheng Mao 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: (t-Bu)2PN=P(i-BuNCH2CH2)3N: New Efficient Ligand for Palladium-Catalyzed C,N Couplings of Aryl and Heteroaryl Bromides and Chlorides and for Vinyl Bromides at Room Temperature.CHEMINFORM, Issue 35 2008Ch. Venkat Reddy 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: Ionic Liquid-Promoted Stereoselective Synthesis of (Z)-Vinyl Bromides by [bmIm]OH under Organic Solvent-Free Conditions: A Green Approach.CHEMINFORM, Issue 6 2008Brindaban C. Ranu 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] Tetrabutylammonium Fluoride Induced Dehydrobromination of Vinyl Bromides to Terminal Acetylenes.CHEMINFORM, Issue 52 2007Masaru Okutani 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] Preference of 4-exo Ring Closure in Copper-Catalyzed Intramolecular Coupling of Vinyl Bromides with Alcohols.CHEMINFORM, Issue 45 2007Yewen Fang 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] Palladium-Catalyzed Hydroxycarbonylation of Aryl and Vinyl Bromides by Mixed Acetic Formic Anhydride.CHEMINFORM, Issue 4 2007Philippe Berger 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] Stereoselective Hydroxycarbonylation of Vinyl Bromides to ,,,-Unsaturated Carboxylic Acids in the Ionic Liquid [BMIM]PF6.CHEMINFORM, Issue 40 2006Xiaodan Zhao 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] A Stereoselective Synthesis of Vinyl Bromides from ,-Bromo-,,,-Unsaturated Ketones Involving Fragmentation of ,,,-Unsaturated Sulfinic Acids.CHEMINFORM, Issue 31 2006A New Approach to the Vitamin D Rings CD Building Blocks. 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] Formal Synthesis of Olivacine via IndolylborateHELVETICA CHIMICA ACTA, Issue 10 2008Minoru Ishikura Abstract Palladium-catalyzed tandem cyclization,cross-coupling reaction of indolylborate 2 and vinyl bromide 5 was successfully applied in a short formal synthesis of olivacine. The reaction of 2 with 5 in the presence of Pd(OAc)2 readily afforded three kinds of products, triene derivative 6 and vinylindole derivative 7, along with a small amount of the piperidine derivative 8 (Scheme,2). On the other hand, the reactions of 2 with bromide 10 or 15 were also examined (Schemes,4 and 5), and their outcome markedly depended on the relative ease of ring closure as a function of ring size. Irradiation of 6 with a high-pressure mercury lamp (,9; Scheme,2), followed by removal of the N -[(benzyloxy)carbonyl] group and subsequent oxidation afforded, after deprotection, pyridocarbazole 23, and the conversion of 23 to olivacine is known (Scheme,6). [source] A Density Functional Theory Study of the Stille Cross-Coupling via Associative Transmetalation.ADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 6 2007Coordinating Solvents, The Role of Ligands Abstract An associative mechanism has been computationally characterized for the Stille cross-coupling of vinyl bromide and trimethylvinylstannane catalyzed by PdL2 (L=PMe3, AsMe3) with or without dimethylformamide as coordinating ligand. All the species along the catalytic cycles that start from both the cis - and the trans -PdL(Y)(vinyl)Br complexes (Y=L or S; L=PMe3, AsMe3 or PH3; S=DMF) have been located in the gas phase and in the presence of polar solvents. Computations support the central role of species trans -PdL(DMF)(vinyl)Br which react by ligand dissociation and stannane coordination in the rate-limiting transmetalation step via a puckered four-coordinate (at palladium) transition state comprised of Pd, Br, Sn and sp2 C atoms. A donating solvent may enter the catalytic cycle assisting isomerization of cis -PdL2(vinyl)Br to trans -PdL(DMF)(vinyl)Br complexes via a pentacoordinate square pyramidal Pd intermediate. In keeping with experimental observations, the activation energies of the catalytic cycles with arsines as Pd ligands are lower than those with phosphines. Polytopal rearrangements from the three-coordinate T-shaped Pd complexes resulting from transmetalation account for the isomerization and the CC bond formation on the reductive elimination step. [source] Plasmabromination , the Selective Way to Monotype Functionalized Polymer SurfacesPLASMA PROCESSES AND POLYMERS, Issue 9 2007Sascha Wettmarshausen Abstract In contrast to other plasma modification processes of polymer surfaces, the bromination is very selective and shows a high yield in CBr groups. The most convenient bromination process was found using bromoform, which was thus preferred to elemental bromine, allyl bromide, vinyl bromide or tert -butylbromide. The bromoform process give yields in CBr up to 40 CBr or more, with only 2,3% co-introduction of O-functionalities whereas allyl bromide results in yields of about 20 CBr and more, but in more than 10% oxygen-containing by-products. CBr groups serve as anchoring points for grafting of molecules, oligomers and pre-polymers of diole or diamine character. [source] 1,3-Chirality Transfer by Fragmentation of Allylsulfinic Acids: A Diastereoselective Approach to Vinyl Bromides Related to trans -Hydrindane or trans -DecalinEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 15 2007Chochrek Abstract Diastereoselective approaches to vinyl bromides from bromoallylic alcohols by fragmentation of the respective allylsulfinic acids have been investigated. Bromoallylic alcohols 1a and 6 were transformed into the respective 1,3-benzothiazol-2-yl sulfides 2a and 7 by the Mitsunobu inversion reaction under modified conditions. The sulfides were then oxidized into sulfones 11a and 12a, respectively. Reduction of 11a and 12a with sodium borohydride gave the respective allylsulfinic acid salts 13a and 15 which, without isolation, were treated with aqeous tartaric acid. The salt 13a gave exclusively 5,-cholestane derivative 14a whereas 15 provided a mixture of the 5, and 5, derivatives 16 and 17 (after deprotection), the former prevailing. In an alternative approach, benzothiazolyl sulfides 2a and 7 were treated sequentially with BH3·THF and LiAlH4 to give thiols 18a and 19a, respectively. Oxidation of thiols 18a and 19a with oxaziridine 21 gave the respective sulfinic acids which, on gentle heating, afforded bromoolefins 14a and 22a, respectively, as the only products. Analogous reaction sequences starting from allylic alcohols devoid of the bromine substituent 1b and 8 have also been studied.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source] Synthesis of Polysubstituted Alkenes by Heck Vinylation or Suzuki Cross-Coupling Reactions in the Presence of a Tetraphosphane,Palladium CatalystEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 6 2003Florian Berthiol Abstract Through the use of [PdCl(C3H5)]2/cis,cis,cis -1,2,3,4-tetrakis[(diphenylphosphanyl)methyl]cyclopentane as a catalyst, a range of vinyl bromides undergo Suzuki cross-couplings with arylboronic acids in good yields. Furthermore, the catalyst can be used at low loadings, even for reactions of sterically hindered substrates. Mediated by this catalyst, stilbene and 1,1-diphenylethylene undergo Heck reactions with aryl halides to give triarylethylene derivatives. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003) [source] Iron-Catalyzed Cross-Coupling Reaction of Vinyl Bromides or Chlorides with Imidazoles in the Absence of Ligands and AdditivesADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 9 2009Jincheng Mao Abstract Highly effective coupling of imidazoles with (E)-vinyl halides can be achieved by using readily available iron catalysts under ligand-free, copper-free and palladium-free conditions. Coupling of (E)-vinyl bromides led to (Z)-products predominantly, while the reactions of (E)-vinyl chlorides afforded (E)-isomers as the major products. [source] Palladium-Catalyzed Intermolecular Three-Component Coupling of Organic Halides with Alkynes and Alkenes: Efficient Synthesis of Oligoene CompoundsADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 14-15 2007Kana Shibata Abstract The intermolecular three-component coupling of aryl or vinyl halides, diarylacetylenes, and monosubstituted alkenes effectively proceeds in the presence of palladium acetate, lithium chloride, and sodium bicarbonate as catalyst, promoter, and base, respectively, in aqueous DMF or DMSO to produce the corresponding 1,3-butadiene or 1,3,5-hexatriene derivatives. Use of dienyl bromides allows the coupling to afford 1,3,5,7-octatetraenes. Under the present catalytic conditions, fulvene derivatives are also formed efficiently by the 1:2 coupling of vinyl bromides and diarylacetylenes without adding the alkenes. [source] Palladium-Catalyzed Cross-Coupling Reactions of Amines with Alkenyl Bromides: A New Method for the Synthesis of Enamines and IminesCHEMISTRY - A EUROPEAN JOURNAL, Issue 2 2004José Barluenga Prof. Dr. Abstract The palladium-catalyzed cross-coupling reaction of alkenyl bromides with secondary and primary amines gives rise to enamines and imines, respectively. This new transformation expands the applicability of palladium-catalyzed CN bond forming reactions (the Buchwald,Hartwig amination), which have mostly been applied to aryl halides. After screening of different ligands, bases, and solvents, the catalytic combination [Pd2(dba)3]/BINAP in the presence of NaOtBu in toluene gave the best results in the cross-coupling of secondary amines with 1-bromostyrene (dba=dibenzylideneacetone, BINAP=2,2,-bis(diphenylphosphino)-1,1,-binaphthyl). The corresponding enamines are obtained cleanly and in nearly quantitative yields. However, steric hindrance seems to be a limitation of the reaction, as amines carrying large substituents are not well converted. The same methodology can be applied to the coupling of secondary amines with 2-bromostyrene. Moreover, the reaction with substituted 2-bromopropenes allows regioselective synthesis of isomerizable terminal enamines without isomerization of the double bond. The best catalytic conditions for the cross-coupling of 1-bromostyrene with primary amines include again the use of the Pd0/BINAP/NaOtBu system. The reaction gives rise to the expected imines in very short times and with low catalyst loadings. A set of structurally diverse imines can be prepared by this methodology through variations in the structure of both coupling partners. However, 2-bromostyrene failed to give good results in this coupling reaction, probably due to product inhibition of the catalytic cycle. Competition experiments of vinyl versus aryl amination reveal that the reaction occurs preferentially on vinyl bromides. La reacción de acoplamiento cruzado de bromuros de alquenilo con aminas secundarias y primarias da lugar a enaminas e iminas respectivamente. Esta nueva transformación expande las aplicaciones de la reacción de formación de enlaces CN catalizada por paladio (aminación Buchwald,Hartwig), que se había limitado fundamentalmente a haluros de arilo. Después de un estudio de diferentes ligandos. bases y disolventes, los mejores resultados en la reacción de acoplamiento cruzado de aminas secundarias con 1-bromoestireno, se obtuvieron para el catalizador constituido por la combinación Pd/BINAP en presencia de NaOtBu en tolueno. Las correspondientes enaminas se obtienen limpiamente y con rendimientos prácticamente cuantitativos. Sin embargo, los impedimentos estéricos en la amina parecen ser una limitación de la reacción, puesto que aminas con sustituyentes voluminosos proporcionan conversiones bajas. La misma metodología puede aplicarse al acoplamiento de aminas secundarias con 2-bromoestireno. Además, la reacción con 2-bromopropenos sustituidos permite obtener de forma regioselectiva enaminas terminales isomerizables, sin que la isomerización del doble enlace tenga lugar. Las mejores condiciones catalíticas para el acoplamiento de aminas primarias con 1-bromoestireno incluyen de nuevo la utilización del sistema Pd(0)/BINAP/NaOtBu. La reacción proporciona las iminas esperadas en tiempos de reacción muy cortos y con baja carga del catalizador. Mediante esta metodología pueden prepararse un conjunto de iminas de gran diversidad estructural, permitiendo variaciones en ambos reactivos de acoplamiento. Sin embargo, la reacción con 2-bromoestireno no produce buenos resultados en este acoplamiento, probablemente debido a inhibición del ciclo catalítico por parte del producto de reacción. Finalmente, experimentos de competencia de aminación vinílica frente a aminación arílica, ponen de manifiesto que esta reacción se produce de forma preferente sobre los bromuros de vinilo. [source] | ||||||||||||||||||||||