
TY  - JOUR
A1  - Thomson, RJ 
A1  - Jackson, WR 
A1  - Haarburger, D 
A1  - Klabunovsky, EI 
A1  - Pavlov, VA 
T1  - The Stereochemistry of Organometallic Compounds. XXIX. Synthesis of Steroidal 1,4-Diphosphine, 1,3-Diphosphine and 1,6-Diphosphine and Their Evaluation as Ligands in Metal Catalyzed Asymmetric Synthesis
JF  - Australian Journal of Chemistry
JO  - Aust. J. Chem.
Y1  - 1987
VL  - 40
IS  - 6
SP  - 1083
EP  - 1106
KW  - 
UR  - https://doi.org/10.1071/CH9871083 
N2  - The steroidal 1,4-diphosphines 3&#945;- and 3&#946;-diphenylphosphino-2a-(2'-diphenylphosphinoethyl)-5&#945;-cholestanes and their 5H-benzo[b] phosphindole derivatives have been prepared and shown to be useful ligands in asymmetric hydrogenation reactions. Interestingly the 3&#945;- and 3&#946;-derivatives lead to opposing enantioselection preferences when used in these reactions. A steroidal 1,3-diphosphine, 3&#945;-diphenylphosphino-2&#945;-diphenylphosphinomethyl-5&#945;-cholestane, has been prepared as a mixture containing some of the 3&#946;-epimer. The 3&#945;-1,3-diphosphine led to similar enantioselection in hydrogenation reactions as the 3&#945;-1,4-diphosphine, and a model is proposed to explain the sense of the enantioselectivity in the 1,4- and 1,3-diphosphines. A steroidal 1,6-diphosphine has also been prepared but leads to lower optical yields in the hydrogenation reactions. These ligands have been shown to lead to only poor to moderate optical yields when used in asymmetric carbon-carbon bond forming reactions. 
ER  -

