Josiphos-type ligands

Togni and Spindler introduced non-C2-symmetric ferrocene-based Josiphos-type ligands [47], which are effective for rhodium-catalyzed hydrogenation of a-(acetami-do)cinnamate, dimethyl itaconate, and / -keto esters. The Josiphos-type hgands have been applied as the stereodefming step in a number of industrial processes, as exemplified the use of PPF- Bu2 for the commercial synthesis of (-i-)-biotin [48], and Xyli-Phos for the preparation of the herbicide (S)-metolachlor [49]. 

Many chiral ferrocene-based bisphosphane ligands with great structural variations have been developed recently. Togni and Spindler introduced non-Crsymmetric ferrocene-based Josiphos type ligands. Josiphos 38 has been found to be effective for Rh-catalyzed hydrogenation of a-acetamidocinnamate, dimethyl itaconate, and P-keto esters. A class of non-Cj-symmetrical ferrocene-based 1,5-diphosphane ligands (TaniaPhos 39) has also been... 

Feringa found that the Josiphos-type ligand 24 was the most effective one for addition of Grignard reagents to low-reactive coumarin 25. The resulting ester enolate 26 also underwent a subsequent aldol reaction with benzaldehyde. The... 

A new protocol for the copper-catalysed asymmetric conjugate 1,4-addition of Grignard reagents to coumarins in the presence of a Josiphos-type ligand (13) has been developed. The corresponding products were formed in high yields and enantiose- 0 lectivities (up to 99% ee). 

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