Vast number of chiral catalysts has been developed for asymmetric hydrogenation reactions. Among them, Rh(I) and Ru(II) diphosphine complexes revealed to be the most efficient for hydrogenation of functionalized alkenes (Scheme S).
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Scheme 2 |
2.3.3 Reduction of Carbon-Carbon Triple Bonds
The carbon-carbon triple bonds are reduced to the corresponding carbon-carbon single bonds when treated with Pt, Pd, Raney Ni catalysts and molecular hydrogen (Scheme 3).
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Scheme 3 |
The carbon-carbon triple bonds are selectively reduced to carbon-carbon double bonds in the presence of Lindlar catalyst (Pd/CaCO3/PbO) or Rosenmund catalyst (Pd/BaSO4/quinoline) and molecular hydrogen (Scheme 4). The hydrogenation of carbon-carbon triple bonds to carbon-carbon double bonds always takes place from same side of the carbon-carbon triple bond providing stereo specifically cis alkenes (Z alkenes).
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Scheme 4 |
For Lindlar Catalyst, see: Lecture 16 |