66938-07-6Relevant articles and documents
First rhodium/phosphoramidite complex-catalyzed enantioselective isomerization of allylic alcohols into aldehydes
Boeda, Fabien,Mosset, Paul,Crévisy, Christophe
, p. 5021 - 5024 (2006)
Primary allylic alcohols are converted into chiral aldehydes in the presence of a catalytic amount (7 mol %) of a monodentate phosphoramidite rhodium catalyst. The aldehydes are isolated in high yields (84-89%) and moderate to good ee's (38-70%). A preliminary mechanistic study showed that the reaction proceeds through a 1,3-H migration pathway.
Optimized iminium-catalysed 1,4-reductions inside the resorcinarene capsule: achieving >90% ee with proline as catalyst
Sokolova, Daria,Tiefenbacher, Konrad
, p. 24607 - 24612 (2021/07/29)
In previous work, we demonstrated that iminium-catalysed 1,4-reductions inside the supramolecular resorcinarene capsule display increased enantioselectivities as compared to their regular solution counterparts. Utilizing proline as the chiral catalyst, enantioselectivities remained below 80% ee. In this study, the reaction conditions were optimized by determining the optimal capsule loading and HCl content. Additionally, it was found that alcohol additives increase the enantioselectivity of the capsule-catalysed reaction. As a result, we report enantioselectivities of up to 92% ee for iminium-catalysed 1,4-reductions relying on proline as the sole chiral source. This is of high interest, as proline is unable to deliver high enantioselectivities for 1,4-reductions in a regular solution setting. Investigations into the role of the alcohol additive revealed a dual role: it not only slowed down the background reaction but also increased the capsule-catalysed reaction rate.
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.
Iminium Catalysis inside a Self-Assembled Supramolecular Capsule: Scope and Mechanistic Studies
Br?uer, Thomas M.,Zhang, Qi,Tiefenbacher, Konrad
, p. 17500 - 17507 (2017/12/15)
Although iminium catalysis has become an important tool in organic chemistry, its combination with supramolecular host systems has remained largely unexplored. We report the detailed investigations into the first example of iminium catalysis inside a supramolecular host. In the case of 1,4-reductions of α,β-unsaturated aldehydes, catalytic amounts of host are able to increase the enantiomeric excess of the products formed. Several control experiments were performed and provided strong evidence that the modulation of enantiomeric excess of the reaction product indeed stems from a reaction on the inside of the capsule. The origin of the increased enantioselectivity in the capsule was investigated. Furthermore, the substrate and nucleophile scope were studied. Kinetic investigations as well as the kinetic isotope effect measured confirmed that the hydride delivery to the substrate is the rate-determining step inside the capsule. The exploration of benzothiazolidines as alternative hydride sources revealed an unexpected substitution effect of the hydride source itself. The results presented confirm that the noncovalent combination of supramolecular hosts with iminium catalysis is opening up new exciting possibilities to increase enantioselectivity in challenging reactions.
Copper-Catalyzed Enantioselective Conjugate Addition to α,β-Unsaturated Aldehydes with Various Organometallic Reagents
Goncalves-Contal, Sylvie,Gremaud, Ludovic,Palais, La?titia,Babel, Lucille,Alexakis, Alexandre
, p. 3301 - 3308 (2016/09/12)
β-Substituted aldehydes constitute a very important class of compounds found in nature. Synthesis of this motif can be envisioned by C-C bond formation on enals. For this purpose, we report herein the development of enantioselective copper-catalyzed conjugate addition of various organometallic reagents to α,β-unsaturated aldehydes with (R)-H8BINAP, (R)-TolBINAP, and (R)-SEGPHOS as chiral ligands. Three sets of conditions were successfully developed and several enals were used. Reactivity and regio- and enantioselectivities were strongly dependent on reaction conditions and substrates. Good to excellent regio- and enantioselectivities were obtained with zinc reagents R2Zn and aluminum reagents R3Al. However, the asymmetric conjugate addition of Grignard reagents afforded only moderate to good regio- and enantioselectivities.
Iminium Catalysis inside a Self-Assembled Supramolecular Capsule: Modulation of Enantiomeric Excess
Br?uer, Thomas M.,Zhang, Qi,Tiefenbacher, Konrad
, p. 7698 - 7701 (2016/07/07)
The noncovalent combination of a supramolecular host with iminium organocatalysis is described. Due to cation–π interactions the reactive iminium species is held inside the host and reacts in this confined environment. The products formed differ up to 92 % ee from the control experiments without added host. A model rationalizing the observed difference is presented.
Copper-catalyzed asymmetric conjugate addition to challenging michael acceptors and synthesis of relevant target molecules
Gremaud, Ludovic,Palais, Laetitia,Alexakis, Alexandre
scheme or table, p. 196 - 200 (2012/07/28)
We report herein the enantioselective Cu-catalyzed conjugate addition of organometallic reagents to sensitive Michael acceptors and their application to the synthesis of relevant target molecules. This is one of the most important methodologies to form a C-C bond in an enantioselective manner. A wide range of α,β-unsaturated aldehydes and β,γ-unsaturated-α- ketoesters has been successfully used. Reactivity, regioand enantioselectivities were strongly dependent on the reaction conditions, therefore moderate to very good results were obtained. Furthermore, γ-substituted-α-ketoesters were used as chiral building blocks for further derivatization with complete retention of the chiral information to obtain key compounds. Schweizerische Chemische Gesellschaft.
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
Expanded scope for the iridium-catalyzed asymmetric isomerization of primary allylic alcohols using readily accessible second-generation catalysts
Mantilli, Luca,Mazet, Clement
supporting information; experimental part, p. 445 - 447 (2010/04/04)
A second generation of chiral (P,N)-iridium catalysts - readily accessible from inexpensive l-serine - displays expanded scope for the asymmetric isomerization of primary allylic alcohols.
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).
