231 research outputs found
The Mizoroki-Heck Reaction with Internal Olefins: Reactivities and Stereoselectivities
The MizorokiāHeck reaction is one of the most valuable reactions for functionalizing CāC double bonds in the presence of a Pd catalyst. This protocol is suitable for the reaction of a C(sp^{2})-halide with a terminal olefin to produce a transā1,2ādisubstituted olefin. However, reports of the MizorokiāHeck reaction of internal olefins are rare and impractical due to the low reactivity of internal olefins and problems of product diastereoselectivity. In this review, we summarize MizorokiāHeck reactions of internal olefins with aryl or alkyl halides to illustrate their reactivities and stereoselectivities
Hybrid Reaction Systems for the Synthesis of Alkylated Compounds based upon Cu-catalyzed Coupling of Radicals and Organometallic Species
A transition metal catalyzed alkylation with an alkyl halide is one of the most difficult reactions to achieve, because of the difficult oxidative addition of an alkylāhalogen bond to a metal, and the tendency of the resulting alkylmetal intermediate to undergo a Ī²āhydride elimination reaction to give an olefin. In this review, we discuss hybrid reaction systems involving Cu catalyzed combination of radicals and organometallic species, which enable facile alkylation reactions to construct CāC and Cāheteroatom bonds. This paper highlights recent progress in arylation, alkenylation, alkynylation, cyclization, addition and introduction of heteroatoms via these hybrid reaction systems
The RIKEN integrated database of mammals
The RIKEN integrated database of mammals (http://scinets.org/db/mammal) is the official undertaking to integrate its mammalian databases produced from multiple large-scale programs that have been promoted by the institute. The database integrates not only RIKENās original databases, such as FANTOM, the ENU mutagenesis program, the RIKEN Cerebellar Development Transcriptome Database and the Bioresource Database, but also imported data from public databases, such as Ensembl, MGI and biomedical ontologies. Our integrated database has been implemented on the infrastructure of publication medium for databases, termed SciNetS/SciNeS, or the Scientistsā Networking System, where the data and metadata are structured as a semantic web and are downloadable in various standardized formats. The top-level ontology-based implementation of mammal-related data directly integrates the representative knowledge and individual data records in existing databases to ensure advanced cross-database searches and reduced unevenness of the data management operations. Through the development of this database, we propose a novel methodology for the development of standardized comprehensive management of heterogeneous data sets in multiple databases to improve the sustainability, accessibility, utility and publicity of the data of biomedical information
Mechanism and Enantioselectivity in Palladium-Catalyzed Conjugate Addition of Arylboronic Acids to Ī²āSubstituted Cyclic Enones: Insights from Computation and Experiment
Enantioselective conjugate additions of arylboronic acids to Ī²-substituted cyclic enones have been previously reported from our laboratories. Air- and moisture-tolerant conditions were achieved with a catalyst derived in situ from palladium(II) trifluoroacetate and the chiral ligand (S)-t-BuPyOx. We now report a combined experimental and computational investigation on the mechanism, the nature of the active catalyst, the origins of the enantioselectivity, and the stereoelectronic effects of the ligand and the substrates of this transformation. Enantioselectivity is controlled primarily by steric repulsions between the t-Bu group of the chiral ligand and the Ī±-methylene hydrogens of the enone substrate in the enantiodetermining carbopalladation step. Computations indicate that the reaction occurs via formation of a cationic arylpalladium(II) species, and subsequent carbopalladation of the enone olefin forms the key carbonācarbon bond. Studies of nonlinear effects and stoichiometric and catalytic reactions of isolated (PyOx)Pd(Ph)I complexes show that a monomeric arylpalladiumāligand complex is the active species in the selectivity-determining step. The addition of water and ammonium hexafluorophosphate synergistically increases the rate of the reaction, corroborating the hypothesis that a cationic palladium species is involved in the reaction pathway. These additives also allow the reaction to be performed at 40 Ā°C and facilitate an expanded substrate scope
Gateways to the FANTOM5 promoter level mammalian expression atlas
The FANTOM5 project investigates transcription initiation activities in more than 1,000 human and mouse primary cells, cell lines and tissues using CAGE. Based on manual curation of sample information and development of an ontology for sample classification, we assemble the resulting data into a centralized data resource (http://fantom.gsc.riken.jp/5/). This resource contains web-based tools and data-access points for the research community to search and extract data related to samples, genes, promoter activities, transcription factors and enhancers across the FANTOM5 atlas. Electronic supplementary material The online version of this article (doi:10.1186/s13059-014-0560-6) contains supplementary material, which is available to authorized users
Tertiary Alkylative Suzuki-Miyaura couplings
The Suzuki-Miyaura coupling is extremely useful to construct Csp2-Csp2 carbon bonds. On the other hand, Csp2-Csp3 coupling reactions are do not work well, and tert-alkylative Suzuki-Miyaura coupling is particularly challenging due to problematic oxidative addition and beta-hydride elimination side reactions. In this short review, we will introduce recent examples of tert-alkylative Suzuki-Miyaura couplings with tert-alkyl electrophiles or -boron reagents. The review will mainly focus on catalyst and product structures and the proposed mechanisms
Electrodeposition of cobalt-chromium alloys from cobalt chloride-N-(n-butyl)pyridinium chloride molten salt
Electrodeposition of cobalt-chromium alloys of different compositions (up to 14 at% Cr) has been carried out onto copper cathode by the pulse potential and the pulse current methods from cobalt chloride-N-(n-butyl)pyridinium chloride (BPC) molten salt containing chromium(II) chloride at 110Ā°C. The magnetic properties of the deposited cobalt-chromium alloys have been investigated. The magnetic polarization of the deposited cobalt-chromium alloys at high fields decreases with the increase of chromium content in the deposit except Co-1.22 at% Cr alloy, with maximum magnetic polarization than the bulk cobalt. The cathodic current efficiency for the deposition of alloy is about 99 %
Electrodeposition of cobalt from cobalt chloride-<i style="">N</i>-(<i style="">n</i>-butyl)pyridinium chloride molten salt
648-653A molten salt system of CoCl2-N-(n-butyl)pyridinium
chloride (BPC) having melting point oC has been developed over
a wide composition range (1:2 to 1:1 mole ratio CoCl2-BPC) and the
electrodeposition of cobalt has been carried out by constant current and
constant potential methods at 110oC. Cobalt cannot be deposited from
a CoCl2-BPC melt containing BPC concentration higher than the mole
ratio of 1:2, whereas it can be deposited from BPC concentration lower than the
mole ratio of 1:2. The deposition reaction mechanisms of cobalt in the CoCl2-BPC
molten bath are revealed by electrochemical analysis. The experimental Tafel
slope of 62 mV dec-1 and the calculated transfer coefficient (āc) of 1 (one) suggest that the rate determining step is a
chemical reaction involving the release of the complexing agents occurring
after first charge transfer step. X-ray diffractometer and scanning electron
microscope have been used to investigate the influence of electrodeposition
conditions and the morphology of the electrodeposited layers. The cathodic
current efficiency for the deposition of cobalt is about 98%
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