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β‐Alkoxy‐ and β‐Hydroxyalkylphosphanes as Ligands in the Stereoselective Hydrogenation — A Comparison
Author(s) -
Börner Armin,
Kless Achim,
Kempe Rhett,
Heller Detlef,
Holz Jens,
Baumann Wolfgang
Publication year - 1995
Publication title -
chemische berichte
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 136
eISSN - 1099-0682
pISSN - 0009-2940
DOI - 10.1002/cber.19951280805
Subject(s) - chemistry , alkoxy group , stereoselectivity , butane , malic acid , ether , medicinal chemistry , metal , ascorbic acid , benzoic acid , stereochemistry , catalysis , organic chemistry , alkyl , food science , citric acid
Optically pure 1,4‐bis(diphenylphosphanyl)‐2‐hydroxy‐butane ( 2 ) and its methyl ether 1 can be conveniently prepared by starting from chiral pool substances such as malic or L‐ascorbic acid. Different pathways to these compounds were elucidated. In one case an interesting migration of an acetalic OH‐protective group was observed. The reaction of the bisphosphanes with Rh 1 or Pd II gave uniform metal complexes. On the basis of X‐ray structural analysis, NMR and IR data it was concluded that in the investigated precatalysts of the type [Rh(COD)(bisphosphane)]BF 4 a coordination of the alkoxy or hydroxy oxygen to the metal does not take place. Nevertheless, significant differences in enantioselectivity and activity could be observed when several prochiral substrates were hydrogenated.