75834-17-2Relevant academic research and scientific papers
A General Organocatalytic System for Enantioselective Radical Conjugate Additions to Enals
Le Saux, Emilien,Ma, Dengke,Bonilla, Pablo,Holden, Catherine M.,Lustosa, Danilo,Melchiorre, Paolo
supporting information, p. 5357 - 5362 (2021/02/01)
Herein, we report a general iminium ion-based catalytic method for the enantioselective conjugate addition of carbon-centered radicals to aliphatic and aromatic enals. The process uses an organic photoredox catalyst, which absorbs blue light to generate radicals from stable precursors, in combination with a chiral amine catalyst, which secures a consistently high level of stereoselectivity. The generality of this catalytic platform is demonstrated by the stereoselective interception of a wide variety of radicals, including non-stabilized primary ones which are generally difficult to engage in asymmetric processes. The system also served to develop organocatalytic cascade reactions that combine an iminium-ion-based radical trap with an enamine-mediated step, affording stereochemically dense chiral products in one-step.
Iridium-Catalyzed Asymmetric Isomerization of Primary Allylic Alcohols Using MaxPHOX Ligands: Experimental and Theoretical Study
Cabré, Albert,Gar?on, Martí,Gallen, Albert,Grisoni, Lorenzo,Grabulosa, Arnald,Verdaguer, Xavier,Riera, Antoni
, p. 4112 - 4120 (2020/07/04)
The asymmetric isomerization of primary allylic alcohols to chiral aldehydes using iridium-catalysts bearing P,N-MaxPHOX ligands has been studied. These catalysts can be fine-tuned as they present three different stereogenic centers to modulate both the reactivity and enantioselectivity of a family of different substrates. The experimental part is supported by a DFT study of the reaction mechanism, which provides new insights into the key steps of this transformation.
Direct Stereoselective Installation of Alkyl Fragments at the β-Carbon of Enals via Excited Iminium Ion Catalysis
Verrier, Charlie,Alandini, Nurtalya,Pezzetta, Cristofer,Moliterno, Mauro,Buzzetti, Luca,Hepburn, Hamish B.,Vega-Pe?aloza, Alberto,Silvi, Mattia,Melchiorre, Paolo
, p. 1062 - 1066 (2018/02/14)
The direct introduction of sp3 carbon fragments at the β position of α,β-unsaturated aldehydes is greatly complicated by competing 1,2-addition manifolds. Previous catalytic enantioselective conjugate addition methods, based on the use of organometallic reagents or ground-state iminium ion activation, could not provide general and efficient solutions. We report herein that, by turning them into strong oxidants, visible light excitation of chiral iminium ions triggers a stereocontrolled radical pathway that exclusively affords highly enantioenriched β-substituted aldehydes bearing a variety of alkyl fragments.
Enantioselective isomerization of primary allylic alcohols into chiral aldehydes with the tol-binap/dbapen/ruthenium(II) catalyst
Arai, Noriyoshi,Sato, Keisuke,Azuma, Keita,Ohkuma, Takeshi
supporting information, p. 7500 - 7504 (2013/07/26)
Efficient isomerization: The title reaction was catalyzed by the [RuCl 2{(S)-tol-binap}{(R)-dbapen}]/KOH system in ethanol at 25°C (see scheme). A series of E- and Z-configured aromatic and aliphatic allylic alcohols, including a simple primary alkyl-substituted compound (E)-3-methyl-2-hepten-1-ol, were transformed into the chiral aldehydes with at least 99 % ee. dbapen=2-dibutylamino-1-phenylethylamine, tol-binap=2,2′- bis(di-4-tolylphosphanyl)-1,1′-binaphthyl. Copyright
Highly enantioselective asymmetric isomerization of primary allylic alcohols with an iridium-N,P complex
Li, Jia-Qi,Peters, Byron,Andersson, Pher G.
supporting information; experimental part, p. 11143 - 11145 (2011/10/31)
Access to chiral aldehydes: The asymmetric isomerization of primary allylic alcohols was studied with a bicyclic phosphine-oxazoline iridium catalyst. This method displays a broad substrate scope and leads to the desired chiral aldehydes with excellent enantioselectivities (see scheme; R1, R 2=Ar or alkyl). Copyright
Improved catalysts for the iridium-catalyzed asymmetric isomerization of primary allylic alcohols based on charton analysis
Mantilli, Luca,Gerard, David,Torche, Sonya,Besnard, Celine,Mazet, Clement
supporting information; experimental part, p. 12736 - 12745 (2011/02/21)
An improved generation of chiral cationic iridium catalysts for the asymmetric isomerization of primary allylic alcohols is disclosed. The design of these air-stable complexes relied on the preliminary mechanistic information available, and on Charton analyses using two preceding generations of iridium catalysts developed for this highly challenging transformation. Sterically unbiased chiral aldehydes that were not accessible previously have been obtained with high levels of enantioselectivity, thus validating the initial hypothesis regarding the selected ligand-design elements. A rationale for the high enantioselectivities achieved in most cases is also presented. Achieving enantioselectivity: An improved generation of chiral cationic iridium catalysts for the asymmetric isomerization of primary allylic alcohols is disclosed. The design of these air-stable complexes relies on preliminary mechanistic information and on Charton analyses using two preceding generations of iridium catalysts developed for this highly challenging transformation (see figure).
Iridium-catalyzed asymmetric isomerization of primary allylic alcohols
Mantilli, Luca,Gerard, David,Torche, Sonya,Besnard, Celine,Mazet, Clement
supporting information; experimental part, p. 5143 - 5147 (2009/12/07)
Nothing to sm(Ir)k at: Under appropriate reaction conditions, iridium hydride catalysts promote the isomerization of primary allylic alcohols. The best catalysts, like (R)-1 (P green, O red, N blue, Ir yellow), deliver the desired chiral aldehydes with excellent enantioselectivity and good yields. Mechanistic hypotheses have been developed on the basis of preliminary investigations.
Asymmetric 1,4-addition of arylboronic acids to α,β-unsaturated aldehydes catalyzed by a chiral diene-rhodium complex
Hayashi, Tamio,Tokunaga, Norihito,Okamoto, Kazuhiro,Shintani, Ryo
, p. 1480 - 1481 (2007/10/03)
Asymmetric 1,4-addition of arylboronic acids to α,β-unsaturated aldehydes proceeded in the presence of a rhodium catalyst (3 mol %) coordinated with a chiral diene ligand ((R,R)-Bn-bod*) to give the corresponding β-arylaldehydes with perfect 1,4-selectivi
Asymmetric conjugate addition of organozinc compounds to α,β-unsaturated aldehydes and ketones with [2.2] paracyclophaneketimine ligands without added copper salts
Braese, Stefan,Hoefener, Sebastian
, p. 7879 - 7881 (2007/10/03)
(Chemical Equation Presented) The ligand makes it possible: The asymmetric conjugate addition of diethylzinc to α,β-unsaturated aldehydes and ketones occurs with catalytic amounts of the paracyclophaneketimine ligand 1 without further additives.
A versatile new catalyst for the enantioselective isomerization of allylic alcohols to aldehydes: Scope and mechanistic studies
Tanaka, Ken,Fu, Gregory C.
, p. 8177 - 8186 (2007/10/03)
A new planar-chiral bidentate phosphaferrocene ligand (2) has been synthesized and structurally characterized. The derived rhodium complex, [Rh(cod)(2)]BF4, serves as an effective catalyst for asymmetric isomerizations of allylic alcohols to aldehydes, furnishing improved yields, scope, and enantioselectivities relative to previously reported methods. The catalyst is air-stable and can be recovered at the end of the reaction. Mechanistic studies establish that the isomerization proceeds via an intramolecular 1,3-hydrogen migration and that the catalyst differentiates between the enantiotopic C1 hydrogens.
