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Transition metal catalyzed asymmetric hydrogenation is one of the most efficient and practical methods for synthesizing chiral compounds
.
It won the Nobel Prize in Chemistry in 2001 for its important scientific significance and great social value .
Figure 1.
Enantioselective hydrogenation of conjugated alkenynes catalyzed by rhodium and cobalt
With QuinoxP*-CoCl 2 -Zn as the preferred catalytic system, excellent catalytic results can be obtained for substrates containing different positions and electrical substituents on the aromatic ring, and finally synthesized with high chemical selectivity and high enantioselectivity.
A series of chiral propargylamine compounds (Figure 2)
.
Figure 2.
Substrate suitability study
Further research results show that the zinc ions generated after the reduction of the divalent cobalt complex by the zinc powder play an important role in promoting the reaction
.
It is speculated that zinc ions are conducive to the formation of highly active cationic cobalt intermediates through the capture of chlorine atoms, and a possible Co(I)-Co(III) redox reaction mechanism is proposed (Figure 3)
Figure 3.
Mechanism study
The hydrogenation reaction can achieve 98% yield and 98.
9% enantioselectivity at a low catalyst usage of 1/2000
.
The hydrogenated product can be used in the synthesis of a variety of important chiral compounds (such as acetyl-CoA carboxylase inhibitors and chiral triazole compounds, etc.
Figure 4.
Application research
The high-yield metal cobalt catalytic asymmetric hydrogenation has made breakthroughs in the past ten years.
For example, Chirik's research group used the bisimine pyridine cobalt and bisphosphine cobalt catalyst system to achieve C=C substrate dehydrogenation amino acids and non-functionalized olefins.
Efficient asymmetric catalytic hydrogenation
.
Zhang Xumu's research group and Lu Zhan's research group used oxazoline imine/pyridine cobalt and electron-rich cobalt bisphosphine catalyst systems to achieve high-efficiency asymmetric catalytic hydrogenation of acrylic acid and terminal olefins
This result was recently published on Angew.