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Pinene‐Derived Monodentate Phosphoramidites for Asymmetric Hydrogenation
Author(s) -
Schmitz Christian,
Leitner Walter,
Franciò Giancarlo
Publication year - 2015
Publication title -
european journal of organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.825
H-Index - 155
eISSN - 1099-0690
pISSN - 1434-193X
DOI - 10.1002/ejoc.201500120
Subject(s) - chemistry , borane , phosphoramidite , asymmetric hydrogenation , denticity , noyori asymmetric hydrogenation , enantioselective synthesis , moiety , ligand (biochemistry) , rhodium , iridium , stereoselectivity , diol , adduct , chiral ligand , organic chemistry , catalysis , combinatorial chemistry , medicinal chemistry , metal , dna , biochemistry , receptor , oligonucleotide
Phosphoramidite ligands based on pinene‐derived chiral amines have been prepared by a straightforward procedure in good yields. The key step of the synthetic protocol is a stereoselective hydrogenation of annulated pinene–pyridine derivatives leading to (diastereoisomeric) secondary amines that were separated and treated with different chlorophosphites to yield the envisaged phosphoramidites. The absolute configurations of the ligands were assigned on the basis of NMR analyses and corroborated by X‐ray diffraction analysis of a borane adduct of a typical ligand. The new ligands were employed in the asymmetric hydrogenation of imines and olefins. The iridium‐catalyzed hydrogenation of imines provided up to 81 % ee , whereas in the rhodium‐catalyzed hydrogenation of functionalized olefins enantioselectivities of up to 99 % ee were achieved. In this particular application, the different chiral elements of the ligand structure led to synergistic effects and the enantioselectivity is dominated by the chiral diol moiety.