19643-68-6Relevant articles and documents
P-chiral ferrocenephospholanes: Synthesis, reactivity, metal complex chemistry and application in the asymmetric hydrogenation of olefins
Gschwend, Bjoern,Pugin, Benoit,Bertogg, Andreas,Pfaltz, Andreas
, p. 12993 - 13007 (2009)
Starting from (R)-N,N-dimethyl-1-ferrocenylethylamine, a diastereoselective ortho-lithiation procedure and a stereoconvergent intramolecular hydrophosphination gave access to P-chiral ferrocenephospholanes. These mono-or bidentate ligands were converted to the corresponding rhodium and iridium complexes, including a chiral version of Crabtree's catalyst, and tested in the asymmetric hydrogenation of functionalized and unfunctionalized olefins. A significant reactivity difference between the rhodium-1,5-cyclooctadiene and the rhodiumnorbornadiene complex was observed during catalyst activation.
Cobalt precursors for high-throughput discovery of base metal asymmetric alkene hydrogenation catalysts
Friedfeld, Max R.,Shevlin, Michael,Hoyt, Jordan M.,Krska, Shane W.,Tudge, Matthew T.,Chirik, Paul J.
, p. 1076 - 1080 (2013)
Asymmetric hydrogenation of alkenes is one of the most widely used methods for the preparation of single enantiomer compounds, especially in the pharmaceutical and agrochemical industries. For more than four decades, precious metal complexes containing rh
Recovery and Recycling of Chiral Iridium(N,P Ligand) Catalysts from Hydrogenation Reactions
Müller, Marc-André,Gruber, Stefan,Pfaltz, Andreas
, p. 1340 - 1345 (2018)
Despite the high efficiency and broad scope of chiral iridium(N,P ligand) complexes as catalysts for asymmetric hydrogenation, the problem of catalyst recovery and recycling has so far attracted little attention. We have found that at the end of a hydrogenation reaction, iridium(N,P ligand) catalysts form dimeric Ir(III) dihydride complexes, which can be converted back to the original precatalysts by addition of COD. Based on these findings, a practically simple protocol for catalyst recovery was devised. The recovered complexes showed essentially the same reactivity and enantioselectivity as the original catalysts. Especially large-scale applications and hydrogenations of less reactive substrates that require high catalyst loadings will benefit from this protocol that allows recovery and reuse of expensive iridium complexes. (Figure presented.).
Combined Theoretical and Experimental Studies Unravel Multiple Pathways to Convergent Asymmetric Hydrogenation of Enamides
Yang, Jianping,Massaro, Luca,Krajangsri, Suppachai,Singh, Thishana,Su, Hao,Silvi, Emanuele,Ponra, Sudipta,Eriksson, Lars,Ahlquist, M?rten S. G.,Andersson, Pher G.
supporting information, p. 21594 - 21603 (2021/12/27)
We present a highly efficient convergent asymmetric hydrogenation of E/Z mixtures of enamides catalyzed by N,P-iridium complexes supported by mechanistic studies. It was found that reduction of the olefinic isomers (E and Z geometries) produces chiral amides with the same absolute configuration (enantioconvergent hydrogenation). This allowed the hydrogenation of a wide range of E/Z mixtures of trisubstituted enamides with excellent enantioselectivity (up to 99% ee). A detailed mechanistic study using deuterium labeling and kinetic experiments revealed two different pathways for the observed enantioconvergence. For α-aryl enamides, fast isomerization of the double bond takes place, and the overall process results in kinetic resolution of the two isomers. For α-alkyl enamides, no double bond isomerization is detected, and competition experiments suggested that substrate chelation is responsible for the enantioconvergent stereochemical outcome. DFT calculations were performed to predict the correct absolute configuration of the products and strengthen the proposed mechanism of the iridium-catalyzed isomerization pathway.
Monohydride-Dichloro Rhodium(III) Complexes with Chiral Diphosphine Ligands as Catalysts for Asymmetric Hydrogenation of Olefinic Substrates
Higashida, Kosuke,Brüning, Fabian,Tsujimoto, Nagataka,Higashihara, Kenya,Nagae, Haruki,Togni, Antonio,Mashima, Kazushi
supporting information, p. 8749 - 8759 (2020/07/04)
We report full details of the synthesis and characterization of monohydride-dichloro rhodium(III) complexes bearing chiral diphosphine ligands, such as (S)-BINAP, (S)-DM-SEGPHOS, and (S)-DTBM-SEGPHOS, producing cationic triply chloride bridged dinuclear rhodium(III) complexes (1 a: (S)-BINAP; 1 b: (S)-DM-SEGPHOS) and a neutral mononuclear monohydride-dichloro rhodium(III) complex (1 c: (S)-DTBM-SEGPHOS) in high yield and high purity. Their solid state structure and solution behavior were determined by crystallographic studies as well as full spectral data, including DOSY NMR spectroscopy. Among these three complexes, 1 c has a rigid pocket surrounded by two chloride atoms bound to the rhodium atom together with one tBu group of (S)-DTBM-SEGPHOS for fitting to simple olefins without any coordinating functional groups. Complex 1 c exhibited superior catalytic activity and enantioselectivity for asymmetric hydrogenation of exo-olefins and olefinic substrates. The catalytic activity of 1 c was compared with that of well-demonstrated dihydride species derived in situ from rhodium(I) precursors such as [Rh(cod)Cl]2 and [Rh(cod)2]+[BF4]? upon mixing with (S)-DTBM-SEGPHOS under dihydrogen.
Improved synthesis of cyclohexane-backbone iridium-complexes of quinoline-phosphine and their applications in asymmetric hydrogenation
Liu, Qibin
, (2020/09/15)
– The iridium-complexes 3 and 4 with cyclohexane-backbone derived from quinoline were easily synthesized. The key step is cis/trans stereoselective reduction of 2-(quinolin-2-yl)cyclohexanone 5 to trans-2-(quinolin-2-yl)cyclohexanol 6 using Al(Oi-Pr)3/i-P
