Rhodium in asymmetric hydrogenation

Replacement of aryl rings by cyclohexyl groups has shown encouraging results. Achiwa and coworkers [114] recommended diphosphines 336 (R = c-CgHj j, Ar = Ph, R tart-BuO, MeO, MeNH) as ligands for rhodium in asymmetric hydrogenation of a,P-unsaturated acids 3.40 (Rg - R - H). The appropriate ketolactone precursor can also be reduced to (R)-pantolactone 1.16. 

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