Asymmetric hydrogenation spiro ligands

In 2002, Zhou and coworkers designed and synthesized a new type of spiro phosphoamidites 1 based on spirobiindane backbone [20]. These spiro monopho sphoramidite ligands 1, especially SIPHOS (la), showed high enantioselectivities (up to 99.7% ee) in the rhodium catalyzed asymmetric hydrogenation of arylenamides (Scheme 8.4) [15]. The reaction was performed under typical conditions with rhodium catalyst, usually produced in situ from [Rh(COD)2 BP.i with 2 equiv of... 

A novel class of complexes, Ir-(5 )-26a, with chiral spiro aminophosphine ligands was found to be effective catalyst for the asymmetric hydrogenation of a-substituted acrylic acids (Scheme 11) [62]. Under mild reaction conditions and at ambient pressure, various a-aryl and alkyl propionic acids were produced with extremely high efficiency (TONS up to 10 000 TOFs up to 6000h ) and excellent enantioselectivity (up to 99% ee). This reaction provides a practically useful method for the preparation of a-aryl propionic acids, a popular class of non-steroid anti-inflammtory reagents. 

The chiral iridium catalyst (258) bearing a tridentate spiro aminophosphine ligand catalysed the asymmetric hydrogenation of ketones in EtOH and KOBu with excellent enantioselectivities (up to 99.9% ee) and extremely high turnover numbers. ... 

Fu Y, Guo XX, Zhu SF, Hu AG, Xie JH, Zhou QL. Rhodium-catalyzed asymmetric hydrogenation of functionalized olefins using monodentate spiro phosphoramidite ligands. J. Org. Chem. 2004 69(14) 4648 655. 

Chiral transition-metal complexes have also been featured in the following reports " of asymmetric carbonyl reductions hydrogenation of / -aryl- -ketoesters 0 using H2 and iridium-bearing spiro pyridine-aminophosphine ligand rhodium in a theoretical study of catalysis involving amino acid-derived ligands and in... 

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