823-76-7Relevant articles and documents
N-H and C-H Bond Activations of an Isoindoline Promoted by Iridium- And Osmium-Polyhydride Complexes: A Noninnocent Bridge Ligand for Acceptorless and Base-Free Dehydrogenation of Secondary Alcohols
Buil, María L.,Esteruelas, Miguel A.,Izquierdo, Susana,Nicasio, Antonio I.,O?ate, Enrique
, p. 2719 - 2731 (2020)
The elusive C-H bond activation of an organic fragment contained in many biologically active molecules and the use of the resulting noninnocent ligand in bimetallic catalysis applied to the acceptorless and base-free dehydrogenation of secondary alcohols has been performed by using the polyhydrides IrH5(PiPr3)2 (1) and OsH6(PiPr3)2 (2). Complex 1 activates the N-H bond of 1,3-bis(6′-methylpyridyl-2′-imino)isoindoline (HBMePHI) to give the mononuclear complex IrH2{κ2-Npy,Nimine(BMePHI)}(PiPr3)2 (3). Both 1 and 2 activate the C(sp2)-H bond at position 4 of the core isoindoline of the BMePHI ligand of 3. The reactions lead to the homobinuclear complex (PiPr3)2H2Ir{μ-(κ2-Npy,Nimine-BMePI-κ2-Nimine,C4iso)}IrH2(PiPr3)2 (4) and the heterobinuclear compound (PiPr3)2H2Ir{μ-(κ2-Npy,Nimine-BMePI-κ2-Nimine,C4iso)}OsH3(PiPr3)2 (5), respectively. The metalated carbon atom of 4 and 5 has a marked nucleophilic character. Thus, it adds the proton of alcohols to afford the respective cations [(PiPr3)2H2Ir{μ-(κ2-Npy,Nimine-BMePHI-κ2-Npy,Nimine)}IrH2(PiPr3)2]+ (6) and [(PiPr3)2H2Ir{μ-(κ2-Npy,Nimine-BMePHI-κ2-Npy,Nimine)}OsH3(PiPr3)2]+ (7), and the corresponding alkoxide. The mononuclear complex 3 and the binuclear compounds 4 and 5 are efficient catalysts for the acceptorless and base-free dehydrogenation of secondary alcohols. The binuclear complexes 4 and 5 are significantly more active than 3. The catalytic synergism is a consequence of the mutual electronic influence of the metals through the bridge. X-ray diffraction analysis data of the structures of 3-5 and the reactivity of 4 and 5 support a noninnocent character of the bridging ligand.
The solvent determines the product in the hydrogenation of aromatic ketones using unligated RhCl3as catalyst precursor
Bartling, Stephan,Chakrabortty, Soumyadeep,De Vries, Johannes G.,Kamer, Paul C. J.,Lund, Henrik,Müller, Bernd H.,Rockstroh, Nils
, p. 7608 - 7616 (2021/12/13)
Alkyl cyclohexanes were synthesized in high selectivity via a combined hydrogenation/hydrodeoxygenation of aromatic ketones using ligand-free RhCl3 as pre-catalyst in trifluoroethanol as solvent. The true catalyst consists of rhodium nanoparticles (Rh NPs), generated in situ during the reaction. A range of conjugated as well as non-conjugated aromatic ketones were directly hydrodeoxygenated to the corresponding saturated cyclohexane derivatives at relatively mild conditions. The solvent was found to be the determining factor to switch the selectivity of the ketone hydrogenation. Cyclohexyl alkyl-alcohols were the products using water as a solvent.
A robust and stereocomplementary panel of ene-reductase variants for gram-scale asymmetric hydrogenation
Nett, Nathalie,Duewel, Sabine,Schmermund, Luca,Benary, Gerrit E.,Ranaghan, Kara,Mulholland, Adrian,Opperman, Diederik J.,Hoebenreich, Sabrina
, (2021/01/25)
We report an engineered panel of ene-reductases (ERs) from Thermus scotoductus SA-01 (TsER) that combines control over facial selectivity in the reduction of electron deficient C[dbnd]C double bonds with thermostability (up to 70 °C), organic solvent tolerance (up to 40 % v/v) and a broad substrate scope (23 compounds, three new to literature). Substrate acceptance and facial selectivity of 3-methylcyclohexenone was rationalized by crystallisation of TsER C25D/I67T and in silico docking. The TsER variant panel shows excellent enantiomeric excess (ee) and yields during bi-phasic preparative scale synthesis, with isolated yield of up to 93 % for 2R,5S-dihydrocarvone (3.6 g). Turnover frequencies (TOF) of approximately 40 000 h?1 were achieved, which are comparable to rates in hetero- and homogeneous metal catalysed hydrogenations. Preliminary batch reactions also demonstrated the reusability of the reaction system by consecutively removing the organic phase (n-pentane) for product removal and replacing with fresh substrate. Four consecutive batches yielded ca. 27 g L?1 R-levodione from a 45 mL aqueous reaction, containing less than 17 mg (10 μM) enzyme and the reaction only stopping because of acidification. The TsER variant panel provides a robust, highly active and stereocomplementary base for further exploitation as a tool in preparative organic synthesis.
Preparation and Degradation of Rhodium and Iridium Diolefin Catalysts for the Acceptorless and Base-Free Dehydrogenation of Secondary Alcohols
Buil, Mariá L.,Collado, Alba,Esteruelas, Miguel A.,G? mez-Gallego, Mar,Izquierdo, Susana,Nicasio, Antonio I.,Onìate, Enrique,Sierra, Miguel A.
, p. 989 - 1003 (2021/05/04)
Rhodium and iridium diolefin catalysts for the acceptorless and base-free dehydrogenation of secondary alcohols have been prepared, and their degradation has been investigated, during the study of the reactivity of the dimers [M(μ-Cl)(I4-C8H12)]2 (M = Rh (1), Ir (2)) and [M(μ-OH)(I4-C8H12)]2 (M = Rh (3), Ir (4)) with 1,3-bis(6′-methyl-2′-pyridylimino)isoindoline (HBMePHI). Complex 1 reacts with HBMePHI, in dichloromethane, to afford equilibrium mixtures of 1, the mononuclear derivative RhCl(I4-C8H12){κ1-Npy-(HBMePHI)} (5), and the binuclear species [RhCl(I4-C8H12)]2{μ-Npy,Npy-(HBMePHI)} (6). Under the same conditions, complex 2 affords the iridium counterparts IrCl(I4-C8H12){κ1-Npy-(HBMePHI)} (7) and [IrCl(I4-C8H12)]2{μ-Npy,Npy-(HBMePHI)} (8). In contrast to chloride, one of the hydroxide groups of 3 and 4 promotes the deprotonation of HBMePHI to give [M(I4-C8H12)]2(μ-OH){μ-Npy,Niso-(BMePHI)} (M = Rh (9), Ir (10)), which are efficient precatalysts for the acceptorless and base-free dehydrogenation of secondary alcohols. In the presence of KOtBu, the [BMePHI]- ligand undergoes three different degradations: Alcoholysis of an exocyclic isoindoline-N double bond, alcoholysis of a pyridyl-N bond, and opening of the five-membered ring of the isoindoline core.
