Application of Monodentate Secondary Phosphine Oxides, a New Class of Chiral Ligands, in Ir(I)-Catalyzed Asymmetric Imine Hydrogenation

Abstract

Take-down policy If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim.Downloaded from the University of Groningen/UMCG research database (Pure): http://www.rug.nl/research/portal. For technical reasons the number of authors shown on this cover page is limited to 10 maximum. ABSTRACTSecondary phosphine oxides were prepared from R 1 PCl 2 and R 2 MgBr, followed by hydrolysis. They were obtained in an enantiopure form by preparative chiral HPLC. These new monodentate ligands were tested in the iridium-catalyzed hydrogenation of imines at 25 bar. Enantioselectivities up to 76% were obtained at L/Ir ) 2. Addition of pyridine (Pyr/Ir ) 1:2) raised the ee to 83%. Using pyridine as an additive allowed reduction of the L/Ir ratio to 1 without reduction of ee.

Transition Metal-Catalyzed Asymmetric Reactions Using P-Chirogenic Diaminophosphine Oxides: DIAPHOXs

“…The first application of P-chirogenic secondary phosphine oxide to Ir-catalyzed asymmetric hydrogenation was reported by Minnaard, Feringa, and de Vries. 19,20) Pd-catalyzed asymmetric allylic alkylation 21) and asymmetric benzylidencyclopropanation 22) were also reported by Dai and Buono, respectively. Simple P-chirogenic secondary phosphine oxides, such as tert-butylphenylphosphine oxide, have been prepared by optical resolution 23,24) or separation of chiral chromatography.…”

“…Simple P-chirogenic secondary phosphine oxides, such as tert-butylphenylphosphine oxide, have been prepared by optical resolution 23,24) or separation of chiral chromatography. 19) A practical method for the asymmetric synthesis of various kinds of P-chirogenic secondary phosphine oxides, however, is not yet established. 25) Therefore the development of an efficient strategy to synthesize various Pchirogenic secondary phosphine oxides or their equivalent in an optically pure form is in high demand.…”

The application of monodentate secondary phosphine oxide ligands in rhodium- and iridium-catalyzed asymmetric hydrogenation

“…10 Substrate 9, 11, 20, and 21 were purchased from commercial suppliers and used as received. Substrate 10, 12, 13, 14, 15, 16, 17, 18, 19, and 22 were prepared according to literature.…”

“…We recently reported on the successful use of monodentate secondary phosphine oxide ligands in iridium-catalyzed asymmetric imine hydrogenation. 10 This study was followed by a report of Haynes and co-workers applying secondary phosphine oxide ligands in palladium-catalyzed asymmetric allylic substitution reactions. 11 Secondary phosphine oxide ligands such as 1 ( Fig.…”

Enantioselective Synthesis of Alcohols and Amines by Iridium‐Catalyzed Hydrogenation, Transfer Hydrogenation, and Related Processes

“…[80] SPOs are highly modular, airstable and can be easily prepared in a two-step one-pot procedure from RPCl 2 and Grignard reagents. Among the several ligands prepared only 80 showed good activity.…”