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Neutral iridium catalysts with chiral phosphine-carboxy ligands for asymmetric hydrogenation of unsaturated carboxylic acids † † Electronic supplementary information (ESI) available: For CIF data of ( S )- 2d , experimental procedures, and characterization data. CCDC 1498903 . For ESI and crystallographic data in CIF or other electronic format see DOI: 10.1039/c6sc03764j Click here for additional data file. Click here for additional data file.

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ABSTRACT

We developed neutral iridium catalysts with chiral spiro phosphine-carboxy ligands (SpiroCAP) for asymmetric hydrogenation of unsaturated carboxylic acids. Different from the cationic Crabtree-type catalysts, the iridium catalysts with chiral spiro phosphine-carboxy ligands are neutral and do not require the use of a tetrakis[3,5-bis(trifluoromethyl)phenyl]borate (BArF–) counterion, which is necessary for stabilizing cationic Crabtree-type catalysts. Another advantage of the neutral iridium catalysts is that they have high stability and have a long lifetime in air. The new iridium catalysts with chiral spiro phosphine-carboxy ligands exhibit unprecedented high enantioselectivity (up to 99.4% ee) in the asymmetric hydrogenations of various unsaturated carboxylic acids, particularly for 3-alkyl-3-methylenepropionic acids, which are challenging substrates for other chiral catalysts.

No MeSH data available.


Deuterium-labeling experiment.
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sch2: Deuterium-labeling experiment.

Mentions: A deuterium-labeling experiment was performed to determine whether the olefin migrated during the hydrogenation reaction (Scheme 2). The absence of deuterium at the α-position of hydrogenation product d-6a clearly showed that the double bond did not migrate during the reaction.


Neutral iridium catalysts with chiral phosphine-carboxy ligands for asymmetric hydrogenation of unsaturated carboxylic acids † † Electronic supplementary information (ESI) available: For CIF data of ( S )- 2d , experimental procedures, and characterization data. CCDC 1498903 . For ESI and crystallographic data in CIF or other electronic format see DOI: 10.1039/c6sc03764j Click here for additional data file. Click here for additional data file.
Deuterium-labeling experiment.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC5384563&req=5

sch2: Deuterium-labeling experiment.
Mentions: A deuterium-labeling experiment was performed to determine whether the olefin migrated during the hydrogenation reaction (Scheme 2). The absence of deuterium at the α-position of hydrogenation product d-6a clearly showed that the double bond did not migrate during the reaction.

View Article: PubMed Central - PubMed

ABSTRACT

We developed neutral iridium catalysts with chiral spiro phosphine-carboxy ligands (SpiroCAP) for asymmetric hydrogenation of unsaturated carboxylic acids. Different from the cationic Crabtree-type catalysts, the iridium catalysts with chiral spiro phosphine-carboxy ligands are neutral and do not require the use of a tetrakis[3,5-bis(trifluoromethyl)phenyl]borate (BArF–) counterion, which is necessary for stabilizing cationic Crabtree-type catalysts. Another advantage of the neutral iridium catalysts is that they have high stability and have a long lifetime in air. The new iridium catalysts with chiral spiro phosphine-carboxy ligands exhibit unprecedented high enantioselectivity (up to 99.4% ee) in the asymmetric hydrogenations of various unsaturated carboxylic acids, particularly for 3-alkyl-3-methylenepropionic acids, which are challenging substrates for other chiral catalysts.

No MeSH data available.