F.A. Rampf, W.A. Herrmann / Journal of Organometallic Chemistry 601 (2000) 138–141
141
to 76% ee; however, the conversion rates are still too
Acknowledgements
low for technical applications.
This work was supported by the Bundesministerium
fu¨r Bildung und Forschung (Bonn, Germany), the
Fonds der Chemischen Industrie (Frankfurt, Germany)
and Novartis Services AG (Basel, Switzerland). We are
grateful to Petra Ankenbauer for experimental
assistance.
4. Experimental
All reactions were carried out using standard Schlenk
techniques in an oxygen-free nitrogen atmosphere. Sol-
vents were dried with standard methods and distilled
under nitrogen. Chiral ferrocenylethyl diphosphines
were prepared following published methods [10]. Their
diastereomeric excess was 96% or higher. Hydroformy-
lation experiments were performed in a Parr 300 ml
stainless-steel autoclave, using dried and degassed
styrene and a 1:1 mixture of hydrogen and carbon
monoxide. The catalysts were formed in situ from
Rh(CO)2(acac) and two equivalents of ligand in
toluene, before the calculated amount of styrene was
added and the mixture transferred to the autoclave
under nitrogen. Modification of the commercially avail-
able autoclave allowed several catalytic reactions to be
run at the same time without cross-contamination of
the different samples. Through this modification the
volume of the reaction mixtures could be reduced to 1.5
ml and the amount of rhodium catalyst to 1 mmol.
Conversions were determined on an HP 5890 gas chro-
matograph with a 12 m HP-1 capillary column and
flame ionization detection using the method of internal
standardization. Enantiomeric excesses of the aldehydes
were measured on a Chrompack CP 9000 gas chro-
matograph (50 m Lipodex A column, carrier gas he-
lium, split injector, flame ionization detector) after
reduction to the corresponding alcohols with sodium
borohydride. Their absolute configuration was deter-
mined by comparison with an authentic sample of
(R)-(+)-2-phenylpropanol.
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