10.1021/om049628z.s002
Ulli Englert
Ulli
Englert
Chunhua Hu
Chunhua
Hu
Albrecht Salzer
Albrecht
Salzer
Elisabetta Alberico
Elisabetta
Alberico
Conformationally Constrained Diphosphines Derived
from (η<sup>6</sup>-(<i>S</i>)-1-(dimethylamino)indane)Cr(CO)<sub>3</sub>: Synthesis
and Application in Enantioselective Hydrogenation
American Chemical Society
2004
dimethylamino
PR 2 group
Conformationally Constrained Diphosphines Derived
donor group combination
enantiopure diphosphine ligands
dimethyl itaconate
PPh 2 group
2004-11-08 00:00:00
Dataset
https://acs.figshare.com/articles/dataset/Conformationally_Constrained_Diphosphines_Derived_from_sup_6_sup_i_S_i_1_dimethylamino_indane_Cr_CO_sub_3_sub_Synthesis_and_Application_in_Enantioselective_Hydrogenation/3317179
Three new enantiopure diphosphine ligands have been prepared starting from [(η<sup>6</sup>-(1-dimethylamino)indane)Cr(CO)<sub>3</sub>] by means of a stereoselective synthetic strategy involving
highly diastereoselective complexation of the Cr(CO)<sub>3</sub> moiety to (<i>S</i>)-(1-dimethylamino)indane,
regioselective substitution in the 7-position with the PPh<sub>2</sub> group, and, after exchange of the
amino group for a chloro substituent with chloroformic esters, introduction of a PR<sub>2</sub> group
(R = Ph, <i>t</i>-Bu, Cy) in the benzylic position. The stereochemical course of the synthesis has
been confirmed by the X-ray determination of the molecular structure of one intermediate
and of one of the three ligands. The ligands have been tested in the rhodium-promoted
enantioselective hydrogenation of methyl (<i>Z</i>)-<i>N</i>-acetamidocinnamate and dimethyl itaconate.
Enantiomeric excesses ranging from 9 to 88% ee have been obtained, depending on the nature
of the R substituent on the ligand, with the donor group combination <i>o</i><i>-</i>PPh<sub>2</sub>/α-PCy<sub>2</sub> <b>(</b><b><i>S</i></b><b>,</b><b><i>R</i></b><b>p)-6c</b> outperforming the other two. The new ligands, which bear the coordinating teeth on the
stiff backbone provided by the indane framework, compare well with the parent conformationally unlocked “Daniphos” ligands: in the hydrogenation of dimethyl itaconate the new
ligand <b>(</b><b><i>S</i></b><b>,</b><b><i>R</i></b><b>p)-6c</b> provides better results as to conversion and enantioselectivity compared
to the analogous acyclic ligand.