- Mild olefin formationviabio-inspired vitamin B12photocatalysis
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Dehydrohalogenation, or elimination of hydrogen-halide equivalents, remains one of the simplest methods for the installation of the biologically-important olefin functionality. However, this transformation often requires harsh, strongly-basic conditions, rare noble metals, or both, limiting its applicability in the synthesis of complex molecules. Nature has pursued a complementary approach in the novel vitamin B12-dependent photoreceptor CarH, where photolysis of a cobalt-carbon bond leads to selective olefin formation under mild, physiologically-relevant conditions. Herein we report a light-driven B12-based catalytic system that leverages this reactivity to convert alkyl electrophiles to olefins under incredibly mild conditions using only earth abundant elements. Further, this process exhibits a high level of regioselectivity, producing terminal olefins in moderate to excellent yield and exceptional selectivity. Finally, we are able to access a hitherto-unknown transformation, remote elimination, using two cobalt catalysts in tandem to produce subterminal olefins with excellent regioselectivity. Together, we show vitamin B12to be a powerful platform for developing mild olefin-forming reactions.
- Bam, Radha,Pollatos, Alexandros S.,Moser, Austin J.,West, Julian G.
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p. 1736 - 1744
(2021/02/22)
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- Cobalt-catalyzed regioselective dehydrohalogenation of alkyl halides with dimethylphenylsilylmethylmagnesium chloride
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Cobalt-catalyzed reactions of haloalkanes with dimethylphenylsilylmethylmagnesium chloride result in highly regioselective dehydrohalogenation. The reaction does not follow the conventional E2 elimination mechanism but includes β-hydride elimination from the corresponding alkylcobalt intermediate. The interesting reaction mechanism of the cobalt-catalyzed dehydrohalogenation offered unique transformations that are otherwise difficult to attain. Copyright
- Kobayashi, Tsuneyuki,Ohmiya, Hirohisa,Yorimitsu, Hideki,Oshima, Koichiro
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supporting information; experimental part
p. 11276 - 11277
(2009/02/05)
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- Preparation and characterisation of a highly active bimetallic (Pd-Ru) nanoparticle heterogeneous catalyst
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The mixed-metal carbonylate cluster [Pd6Ru6(CO)24]2- was used as a single-source precursor in the synthesis of a highly active hydrogenation catalyst (stoichiometry PdRu) which has been characterised by electron microscopy and X-ray absorption spectroscopy: PdRu readily hydrogenates alkenes and naphthalene (the latter predominantly to cis-decalin) under mild conditions.
- Raja, Robert,Sankar, Gopinathan,Hermans, Sophie,Shephard, Douglas S.,Bromley, Stefan,Thomas, John Meurig,Johnson, Brian F.G.
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p. 1571 - 1572
(2007/10/03)
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- Conversions of 1-decene under the action of complex zirconium-containing catalysts
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A study has been made of the bulk conversion of 1-decene on complex catalysts containing Zr(OC3H7)4 and Zr(OCO-iso-C3H7)4 and Al(C2H5)3, (C2H5)2AlCl or (C2H5)1·5AlCl1·5 at temperatures of 80-110°C. It has been established that the total conversion of 1-decene under the action of the given catalysts depends on the nature of the organoaluminium cocatalyst and decreases in the order (C2H5)1·5AlCl1·5 > (C2H5)2AlCl > Al(C2H5)3. The main products of conversions of 1-decene are 2-ethyl-1-decene, dimers and trimers of 1-decene, and also 2-decene. The yield of 2-ethyl-1-decene increases with an increasing Al/Zr molar ratio and reaches 20 mole/mole zirconium compound in the catalyst. The probable mechanism of the conversions occurring is proposed.
- Startseva,Matkovskii,Mel'nikov
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p. 136 - 142
(2007/10/03)
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- The Conversion of Primary Amines into Olefins: a Mild Alternative to the Hofmann Elimination
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Use of the pentacyclic pyrylium salt (1) allows a two-step conversion of the amine RR'CHCH2NH2 into RR'C=CH2 in high yield under mild conditions.
- Katritzky, Alan R.,El-Mowafy, Azzahra M.
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