- A Bulky Three-Hindered Quadrant Bisphosphine Ligand: Synthesis and Application in Rhodium-Catalyzed Asymmetric Hydrogenation of Functionalized Alkenes
-
A bulky three-hindered quadrant bisphosphine ligand, di-1-adamantylphosphino(tert-butylmethylphosphino)methane, named BulkyP*, has been synthesized via a convergent short pathway with chromatography-free procedures. The ligand is a crystalline solid and can be readily handled in air. Its rhodium(I) complex exhibits very high enantioselectivities and catalytic activities in the asymmetric hydrogenation of functionalized alkenes.
- Sawatsugawa, Yuuki,Tamura, Ken,Sano, Natsuhiro,Imamoto, Tsuneo
-
supporting information
p. 8874 - 8878
(2019/11/03)
-
- Utilization of optically active secondary phosphine-boranes: synthesis of P-chiral diphosphines and their enantioinduction ability in rhodium-catalyzed asymmetric hydrogenation
-
Abstract Both enantiomers of tert-butylmethylphosphine-borane have been used for the synthesis of P-chiral diphosphines and/or their borane complexes. The enantiopure borane complex of 1,2-bis(tert-butylmethylphosphino)ethane (t-Bu-BisP?) was prepared in
- Imamoto, Tsuneo,Horiuchi, Yumi,Hamanishi, Eri,Takeshita, Satoshi,Tamura, Ken,Sugiya, Masashi,Yoshida, Kazuhiro
-
p. 6471 - 6480
(2015/08/18)
-
- Practical enantioselective hydrogenation of α-aryl- and α-carboxyamidoethylenes by rhodium(I)-{1,2-bis[(o-tert-butoxyphenyl) (phenyl)phosphino]ethane}
-
The rhodium(I)-{1,2-bis[(o-tert-butoxyphenyl)(phenyl)phosphino]ethane} [Rh(I)-(t-Bu-SMS-Phos)] catalyst system displayed prime efficiency in the hydrogenation of large series of aamidostyrenes and a-amidoacrylates. Up to >99.9% enantiomeric excesses coupl
- Mohar, Barbara,Stephan, Michel
-
p. 594 - 600
(2013/05/09)
-
- Rigid P-chiral phosphine ligands with tert -butylmethylphosphino groups for rhodium-catalyzed asymmetric hydrogenation of functionalized alkenes
-
Both enantiomers of 2,3-bis(tert-butylmethylphosphino)quinoxaline (QuinoxP*), 1,2-bis(tert-butylmethylphosphino)benzene (BenzP*), and 1,2-bis(tert-butylmethylphosphino)-4,5-(methylenedioxy)benzene (DioxyBenzP*) were prepared in short steps from enantiopure (S)- and (R)-tert-butylmethylphosphine-boranes as the key intermediates. All of these ligands were crystalline solids and were not readily oxidized on exposure to air. Their rhodium complexes exhibited excellent enantioselectivities and high catalytic activities in the asymmetric hydrogenation of functionalized alkenes, such as dehydroamino acid derivatives and enamides. The practical utility of these catalysts was demonstrated by the efficient preparation of several chiral pharmaceutical ingredients having an amino acid or a secondary amine component. A rhodium complex of the structurally simple ligand BenzP* was used for the mechanistic study of asymmetric hydrogenation. Low-temperature NMR studies together with DFT calculations using methyl α-acetamidocinnamate as the standard model substrate revealed new aspects of the reaction pathways and the enantioselection mechanism.
- Imamoto, Tsuneo,Tamura, Ken,Zhang, Zhenfeng,Horiuchi, Yumi,Sugiya, Masashi,Yoshida, Kazuhiro,Yanagisawa, Akira,Gridnev, Ilya D.
-
supporting information; experimental part
p. 1754 - 1769
(2012/03/11)
-
- Development of an asymmetric hydrogenation route to (S)- N -Boc-2,6-dimethyltyrosine
-
An improved, simpler and potentially more economical route to (S)-N-Boc-2,6-dimethyltyrosine 1, based on a previously published route, is presented. Key modifications were to prepare the dehydroaminoacid hydrogenation substrate 6 in a one-pot process directly from serine methyl ester and 4-iodo-3,5-dimethylphenyl acetate 4 and to identify a significantly more active asymmetric hydrogenation catalyst that allowed a 5-fold reduction in catalyst loading.
- Praquin, Celine F. B.,De Koning, Pieter D.,Peach, Philip J.,Howard, Roger M.,Spencer, Sarah L.
-
p. 1124 - 1129
(2012/01/06)
-
- A convenient asymmetric synthesis of the unnatural amino acid 2,6-dimethyl-L-tyrosine
-
The title compound was prepared in high optical purity by a five-step synthesis from 3,5-dimethylphenol on a kilogram scale. The key steps were a modified palladium-catalyzed coupling of an aryl iodide with methyl 2-acetamidoacrylate and hydrogenation of the resulting sterically hindered dehydroamino acid 4 using [Rh(1,5-COD)(R,R-DIPAMP)]BF4 as catalyst.
- Dygos,Yonan,Scaros,Goodmonson,Getman,Periana,Beck
-
p. 741 - 743
(2007/10/02)
-