- Unexpected Dehydrogenation of a Cyclohexyl Group at Low Temerature through Protonation of RuH3(η5-C5Me5)(PCy3) (Cy = cyclohexyl). X Ray Structure of 5-C5Me5)Ru((C6H9)P(C6H11)2)>BF4
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Low temperature protonation of RuH3(η5-C5Me5)(PR3) (R = Pri, Ph, cyclohexyl) leads either to decomposition (R = Pri) to a mixture of cis- and trans-5-C5Me5)(PR3)2>BF4 (R = Ph), or to dehydrogenation of a cyclohexyl group to afford the complex 5-C5Me5)((C6H9)P(C6H11)2)>BF4 which shows a strong agostic interaction beween a C-H bond of the cyclohexyl group and the metal; a possible application of the later observation is proposed for the dehydrogenation of alkenes.
- Arliguie, Therese,Chaudret, Bruno,Jalon, Felix,Lahoz, Fernando
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- Structural, Kinetic, and Computational Characterization of the Elusive Arylpalladium(II)boronate Complexes in the Suzuki-Miyaura Reaction
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The existence of the oft-invoked intermediates containing the crucial Pd-O-B subunit, the “missing link”, has been established in the Suzuki-Miyaura cross-coupling reaction. The use of low-temperature, rapid injection NMR spectroscopy (RI-NMR), kinetic studies, and computational analysis has enabled the generation, observation, and characterization of these highly elusive species. The ability to confirm the intermediacy of Pd-O-B-containing species provided the opportunity to clarify mechanistic aspects of the transfer of the organic moiety from boron to palladium in the key transmetalation step. Specifically, these studies establish the identity of two different intermediates containing Pd-O-B linkages, a tri-coordinate (6-B-3) boronic acid complex and a tetra-coordinate (8-B-4) boronate complex, both of which undergo transmetalation leading to the cross-coupling product. Two distinct mechanistic pathways have been elucidated for stoichiometric reactions of these complexes: (1) transmetalation via an unactivated 6-B-3 intermediate that dominates in the presence of an excess of ligand, and (2) transmetalation via an activated 8-B-4 intermediate that takes place with a deficiency of ligand.
- Thomas, Andy A.,Wang, Hao,Zahrt, Andrew F.,Denmark, Scott E.
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- Direct β-Alkylation of Ketones and Aldehydes via Pd-Catalyzed Redox Cascade
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We report a direct β-alkylation of ketones and aldehydes with simple alkyl bromides through a Pd-catalyzed redox-cascade strategy. The use of a Cu cocatalyst is important for improved efficiency. The reaction is redox-neutral, without the need for strong acids or bases. Both cyclic and acyclic ketones, as well as α-branched aldehydes, are suitable substrates for coupling with secondary and tertiary alkyl bromides. Concise formal synthesis of Zanapezil is achieved using this β-alkylation method.
- Wang, Chengpeng,Dong, Guangbin
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supporting information
p. 6057 - 6061
(2018/05/14)
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- Vinyl and carbene ruthenium(II) complexes from hydridoruthenium(II) precursors
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The reactions of the hydrido compounds [RuHCl(CO)(L)2] {L = PiPr3 (1), PCy3 (2)} with HC≡CR (R = H, Ph, tBu) afforded by insertion of the alkyne into the Ru-H bond the corresponding vinyl complexes [RuCl(CH=CHR)-(CO)(L)su
- Jung, Stefan,Brandt, Carsten D.,Wolf, Justin,Werner, Helmut
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p. 375 - 383
(2007/10/03)
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