Josiphos xyliphos

The optimized process operates at 80 bar hydrogen and 50 °C with a catalyst generated in situ from [Ir(cod)Cl]2 and the Josiphos ligand PPF-PXyl2 (short name Xyliphos) at a SCR of >1000000. Complete conversion is reached within 3—4h, the initial TOFs exceed 1 800 000 h 1, and the ee is about 80%. This process is now operated by Syngenta on a scale of >10000 ty-1 [127]. 

Figure 3.36 a The original Josiphos ligand b the Ir-xyliphos complex used in the Ciba-Geigy metolachlor process. 

Nowadays enantioselective synthesis of the herbicide (5)-metolachlor (Dual Magnum) is, to our knowledge, one of the most successful commercial applications of asymmetric C=N bond hydrogenation. Developed by Blaser and Spindler as a key step in the technical synthesis of (5)-metolachlor, the enantioselective hydrogenation of an imine intermediate 193 proceeds in the presence of an iridium ferrocenyl-diphosphine catalyst bearing a Solvias Josiphos-type chiral ligand (/ )-Xyliphos to give... 

The chelating phosphine 2.56 is called DIPAMP. It was found to be effective for the industrial manufacture of l-DOPA by Knowles. The ligand 2.57 is also a chiral chelating phosphine, but it is made from ferrocene. It is called Josiphos or Xyliphos depending on the R and R groups. It is used for the industrial manufacture of (S)-metolachlor (see Section 5.1.2). 

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