1007-03-0Relevant articles and documents
An efficient and transition metal free protocol for the transfer hydrogenation of ketones as a continuous flow process
Sedelmeier, Joerg,Ley, Steven V.,Baxendale, Ian R.
, p. 683 - 685 (2009)
We report the efficient reduction of a selection of ketones to the corresponding secondary alcohols using only catalytic amounts of LiOtBu in iPrOH facilitated by using a continuous flow reactor.
Efficient transfer hydrogenation of ketones in the presence of ruthenium N-heterocyclic carbene catalysts
Enthaler, Stephan,Jackstell, Ralf,Hagemann, Bernhard,Junge, Kathrin,Erre, Giulia,Beller, Matthias
, p. 4652 - 4659 (2006)
Novel ruthenium carbene complexes have been in situ generated and tested for the transfer hydrogenation of ketones. Applying Ru(cod)(methylallyl)2 in the presence of imidazolium salts in 2-propanol and sodium-2-propanolate as base, turnover frequencies up to 346 h-1 have been obtained for reduction of acetophenone. A comparative study involving ruthenium carbene and ruthenium phosphine complexes demonstrated the higher activity of ruthenium carbene complexes.
Products from solvolysis reactions that form (2-phenylcyclopropyl)carbinyl cations
Chandrasena, R. Esala P.,Aebisher, David,Newcomb, Martin
, p. 974 - 977 (2005)
Products from solvolytic reactions that form the (2-phenylcyclopropyl) carbinyl cation were determined. The majority of products (> 98%) derived from the 1-phenyl-3-butenyl cation, consistent with reports by Wiberg and co-workers. Small amounts of products derived from the 1-phenyl-1- cyclopropylmethyl cation also were found; these products were previously predicted to be formed from reactions of the title cation. Although the 1-phenyl-1-cyclopropylmethyl cation is considerably more stable than the 1-phenyl-3-butenyl cation, it is not kinetically accessible under a variety of solvolytic conditions. Copyright
On the Mechanism of the Reduction of Some Ketones by Organotin Hydrides.Hydride Transfer, Electro-Transfer-Hydrogen-Atom Abstraction, or Free Radical Addition.
Tanner, Dennis D.,Diaz, Gilberto E.,Potter, Alan
, p. 2149 - 2154 (1985)
Three aromatic-aliphatic ketones, cyclopropyl phenyl ketone, α,α,α-trifluoroacetophenone and α-fluoroacetophenone, are reduced by triphenyltin hydride by an initiated homolytic reaction to yield organic stannoxides.The reactivity is is not markedly dependent upon solvent polarity.The unitiated reduction with triphenyltin hydride of the more reactive electronegatively substituted fluorinated alkyl-aromatic ketones show a solvent-dependent reactivity.The reactivity increases as the solvent becomes more polar.Both homolytic and heterolytic processes occur in the more polar solvents.The homol ytic reaction appears to be initiated by an electron-transfer process, and the propagation sequence, likewise, contains an electron-transfer step.It appears that in the propagation step the donor-acceptor ability of the reagents determine whether the homolityc reaction proceeds by a radical addition of a tin to the carbonyl oxygen or whether electron transfer occurs prior to tin-oxygen bond formation.A consideration of the timing of these processes suggests a merged mechanism where the donor-acceptor ability of the reagents determines the extent of electron transfer in or after the transition state.
Distinct Promotive Effects of 1,8-Diazabicyclo[5.4.0]undec-7-ene (DBU) on Polymer Supports in Copper-Catalyzed Hydrogenation of C=O Bonds
Watari, Ryo,Matsumoto, Norio,Kuwata, Shigeki,Kayaki, Yoshihito
, p. 4501 - 4507 (2017)
An amidine base-containing polymer, polystyrene-bound 1,8-diazabicyclo[5.4.0]undec-7-ene (PS-DBU), proved to serve as a prominent catalyst support. The combined use of selected copper salts with PS-DBU in the catalytic hydrogenation of acetophenone qualifies DBU as beneficial to generate catalytically active species and stabilize them on the polymer. Catalyst preparation and characterization reveal that the active copper species is in a low-valent state and the nanosized particles possibly grow on the amidine structure. The high immobilization ability of PS-DBU almost entirely prohibited copper leaching to the product over six cycles of hydrogenation and catalyst recovery. The copper catalyst attached to PS-DBU specifically promotes the hydrogenation of various ketones and aldehydes under 10 atm of H2 at 90 °C to afford alcoholic products in satisfactory yields.
Molecularly Defined Manganese Pincer Complexes for Selective Transfer Hydrogenation of Ketones
Perez, Marc,Elangovan, Saravanakumar,Spannenberg, Anke,Junge, Kathrin,Beller, Matthias
, p. 83 - 86 (2017)
For the first time an easily accessible and well-defined manganese N,N,N-pincer complex catalyzes the transfer hydrogenation of a broad range of ketones with good to excellent yields. This cheap earth abundant-metal based catalyst provides access to useful secondary alcohols without the need of hydrogen gas. Preliminary investigations to explore the mechanism of this transformation are also reported.
Transfer Hydrogenation of Carbonyl Derivatives Catalyzed by an Inexpensive Phosphine-Free Manganese Precatalyst
Bruneau-Voisine, Antoine,Wang, Ding,Dorcet, Vincent,Roisnel, Thierry,Darcel, Christophe,Sortais, Jean-Baptiste
, p. 3656 - 3659 (2017)
A very simple and inexpensive catalytic system based on abundant manganese as transition metal and on an inexpensive phosphine-free bidendate ligand, 2-(aminomethyl)pyridine, has been developed for the reduction of a large variety of carbonyl derivatives with 2-propanol as hydrogen donor. Remarkably, the reaction proceeds at room temperature with low catalyst loading (down to 0.1 mol %) and exhibits a good tolerance toward functional groups. High TON (2000) and TOF (3600 h-1) were obtained.
Evidence for heterolytic cleavage of a cyclic oxonium ylide: Implications for the mechanism of the Stevens [1,2]-shift
Hosseini, Seyedeh Nargess,Johnston, Jeffrey R.,West
, p. 12654 - 12656 (2017)
Formation and rearrangement of several oxonium ylides containing cyclopropylcarbinyl migrating groups were studied. Efficient ring-contraction by [1,2]-shift to form cyclopropane-substituted cyclobutanones was observed, with no competing cyclopropane fragmentation. Substitution with the hypersensitive mechanistic probe (trans,trans-2-methoxy-3-phenylcyclopropyl)methyl led to cyclopropane fragmentation via an apparent heterolytic pathway, providing the first evidence for ion pair intermediates from ylide cleavage, and suggesting a possible alternative heterolytic mechanism for the Stevens [1,2]-shift.
Phosphine-NHC Manganese Hydrogenation Catalyst Exhibiting a Non-Classical Metal-Ligand Cooperative H2 Activation Mode
Buhaibeh, Ruqaya,Filippov, Oleg A.,Bruneau-Voisine, Antoine,Willot, Jérémy,Duhayon, Carine,Valyaev, Dmitry A.,Lugan, No?l,Canac, Yves,Sortais, Jean-Baptiste
, p. 6727 - 6731 (2019)
Deprotonation of the MnI NHC-phosphine complex fac-[MnBr(CO)3(κ2P,C-Ph2PCH2NHC)] (2) under a H2 atmosphere readily gives the hydride fac-[MnH(CO)3(κ2P,C-Ph2PCH2NHC)] (3) via the intermediacy of the highly reactive 18-e NHC-phosphinomethanide complex fac-[Mn(CO)3(κ3P,C,C-Ph2PCHNHC)] (6 a). DFT calculations revealed that the preferred reaction mechanism involves the unsaturated 16-e mangana-substituted phosphonium ylide complex fac-[Mn(CO)3(κ2P,C-Ph2P=CHNHC)] (6 b) as key intermediate able to activate H2 via a non-classical mode of metal-ligand cooperation implying a formal λ5-P–λ3-P phosphorus valence change. Complex 2 is shown to be one of the most efficient pre-catalysts for ketone hydrogenation in the MnI series reported to date (TON up to 6200).
Practical (asymmetric) transfer hydrogenation of ketones catalyzed by manganese with (chiral) diamines ligands
Wang, Ding,Bruneau-Voisine, Antoine,Sortais, Jean-Baptiste
, p. 31 - 36 (2018)
The reduction of ketones with 2-propanol as reductant was achieved using an in-situ generated catalytic system based on manganese pentacarbonyl bromide, as metal precursor, and ethylenediamine as ligand. The reaction proceeds in high yield at 80 °C, in 3 h, with 0.5 mol% of catalyst. In the presence of chiral (1R,2R)-N,N′-dimethyl-1,2-diphenylethane-1,2-diamine, as the ligand, sterically hindered alcohols were produced with enantiomeric excess up to 90%.
