2, 3-Bis(dialkylphosphino)pyrazine derivative, process of producing the same, and metal complex having the same as ligand
申请人:Imamoto Tsuneo
公开号:US20070021610A1
公开(公告)日:2007-01-25
An optically active 2,3-bis(dialkylphosphino)pyrazine derivative represented by formula (1) is disclosed. The pyrazine derivative is preferably a quinoxaline derivative represented by formula (2). In formula (1) and (2), R
1
is preferably a t-butyl or adamantyl group, and R
2
is preferably a methyl group.
wherein R
1
is a substituted or unsubstituted, straight chain or branched alkyl group having 2 to 10 carbon atoms; R
2
is a substituted or unsubstituted, straight chain or branched alkyl group having fewer carbon atoms than R
1
; and R
3
and R
4
, which may be the same or different, are each a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, or R
3
and R
4
are taken together to form a saturated or unsaturated ring.
wherein R
1
and R
2
are as defined above; and R
5
is a monovalent substituent.
Optically-active bis(alkynylphosphino) ethane-borane derivative and process for producing the same
申请人:Imamoto Tsuneo
公开号:US20080221362A1
公开(公告)日:2008-09-11
An optically-active bis(alkynylphosphino)ethane-borane derivative represented by formula (1):
wherein R
1
and R
2
, which may be the same or different, each represent an alkyl group, a phenyl group, an alkylsilyl group or a hydrogen atom; R
3
represents a branched alkyl group, an alicyclic hydrocarbon group or an aromatic hydrocarbon group; and the asterisk * indicates an optically-active site.
The derivative (1) is prepared by bromination of, e.g., an (S)-t-butylmethylphosphine-borane, reaction with an alkynyl lithium, deprotonation, followed by oxidative coupling. Deprotection of the derivative (1) by deboranation gives an optically-active bis(alkynylphosphino)ethane derivative useful as a ligand providing an asymmetric catalyst for catalytic asymmetric synthesis. The asymmetric catalyst having the ligand exhibits high selectivity and catalyst activity.
An Air-Stable P-Chiral Phosphine Ligand for Highly Enantioselective Transition-Metal-Catalyzed Reactions
作者:Tsuneo Imamoto、Keitaro Sugita、Kazuhiro Yoshida
DOI:10.1021/ja053458f
日期:2005.8.1
A new P-chiralphosphineligand, (R,R)-2,3-bis(tert-butylmethylphosphino)quinoxaline, has been prepared by the reaction of enantiomerically pure tert-butylmethylphosphine-borane with 2,3-dichloroquinoxaline. This ligand, in contrast to most of the previously reported P-chiralligands, is an air-stable solid and exhibits excellent enantioselectivities in both Rh-catalyzed asymmetric hydrogenations and
Mechanistic Studies of the Palladium-Catalyzed Ring Opening of Oxabicyclic Alkenes with Dialkylzinc
作者:Mark Lautens、Sheldon Hiebert、Jean-Luc Renaud
DOI:10.1021/ja010498k
日期:2001.7.1
The mechanism of the palladium-catalyzed ring opening of oxabicyclicalkenes with dialkylzinc has been studied. Experiments which rule out a π-allyl mechanism were carried out. Trapping carbometalated products and synthesis and successful reaction of alkyl palladium species provided strong evidence in favor of an enantioselective carbopalladation as the key step in the mechanism. The studies also suggest
Air-stable P-Chiral Bidentate Phosphine Ligand with (1-Adamantyl)methylphosphino Group
作者:Tsuneo Imamoto、Atsushi Kumada、Kazuhiro Yoshida
DOI:10.1246/cl.2007.500
日期:2007.4.5
Air-stable diphosphine ligand, (R,R)-2,3-bis((1 -adamantyl)-methylphosphino)quinoxaline, was prepared by the reaction of enantiomerically pure (S )-(l-adamantyl)methylphosphine-borane with 2,3-dichloroquinoxaline. The ligand exhibited excellent enantioselectivities in Rh-catalyzed asymmetric hydrogenation and Pd-catalyzed asymmetric ring-opening reaction.