Impact on hydrogenation catalytic cycle of the R groups' cyclic feature in "R-SMS-Phos".

A series of R-SMS-Phos ligands was evaluated in the Rh(I)-catalyzed hydrogenation of a set of olefins showing a marked influence of the cyclic nature and structure of the R groups. Overall, cPen- and Cy-SMS-Phos performed efficiently, while Ph- and Bn-SMS-Phos exhibited slower kinetics and furnished lower ee's also compared with C(6)F(5)CH(2)-SMS-Phos. The Rh(I)-(Cy-SMS-Phos) catalyst was screened under mild conditions displaying excellent enantioselectivities and high TOFs. Cases of catalysis under catalyst or substrate control were identified.