1528
G. S. Fonseca et al.
LETTER
ketones were distilled under argon prior to use. All other reagents
were obtained from commercial sources (PA grade, Aldrich or
Acros) and used as received. NMR spectra were recorded on a Vari-
an Inova 300 spectrometer. Infrared spectra were performed on a
Bomem B-102 spectrometer. Mass spectra were obtained using a
GC/MS Shimadzu QP-5050 (EI, 70eV). Gas chromatography anal-
yses were performed with a Hewlett-Packard-5890 Gas Chromato-
graph with a FID detector and 30-meter capillary column with a
dimethylpolysiloxane stationary phase. The products were analyzed
by GC (comparison of the retention times with authentic samples)
and characterized by GC-MS, IR, 1H and 13C NMR. The hydroge-
nation reactions were carried out in a modified Fischer–Porter bottle
immersed in a silicon oil bath and connected to a hydrogen tank.
The fall in the hydrogen pressure in the tank was monitored with a
pressure transducer interfaced through a Novus converter to a PC
and the data workup via Microcal Origin 5.0. The temperature was
maintained at 75 °C by a hot-stirring plate connected to a digital
controller (ETS-D4 IKA). A deliberated stirring at 800 rpm was
used.
Acknowledgment
Thanks are due to CNPq and FAPERGS for partial financial support
and scholarships.
References
(1) (a) Abdel-Magid, A. F. Reductions in Organic Synthesis,
ACS Symposium Series 641; American Chemical Society:
Washington DC, 1996. (b) Hudlick, M. Reductions in
Organic Chemistry, ACS Monograph 188, 2nd ed.;
American Chemical Society: Washington DC, 1996.
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(3) Noyori, R.; Ohkuma, T. Angew. Chem. Int. Ed. 2001, 40, 40.
(4) Cusack, R. W. Chem. Eng. Prog. 1996, 92, 56.
(5) Dupont, J.; de Souza, R. F.; Suarez, P. A. Z. Chem. Rev.
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F. P.; Teixeira, S. R. J. Am. Chem. Soc. 2002, 124, 4228.
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(10) For examples of selective hydrogenation of arenes see:
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Org. Synth. 2002, 79, 236.
Hydrogenation Experiments
Nanoparticles Synthesis: In a Fischer–Porter bottle, the organo-
metallic precursor [Ir(cod)Cl]2 (0,052 mmol) dispersed in BMI·PF6
(1 mL) was treated with 4 atm of hydrogen at 75 °C and constant
stirring, resulting in a black suspension after around 10 min. The
black colloidal suspension obtained was washed with acetone (3 × 5
mL), separated by centrifugation and dried under reduced pressure
(90% yield supposing that all material weighted are constituted of
metallic iridium).
Biphasic System: In a typical experiment (ketone/Ir = 250), 13
mmol of ketone was added in a Fischer–Porter bottle reactor con-
taining the iridium nanoparticles (0.052 mmol) dispersed in
BMI·PF6 (1 mL). To the system was admitted 4 atm constant pres-
sure of molecular hydrogen and it was maintained at 75 °C with
constant stirring. The products were obtained by simple decantation
and analyzed by a GC. The respective time and conversions are
shown in Table 1 and Table 2.
Solventless Conditions: The ketone was added over isolated iridi-
um nanoparticles and the mixture was maintained over constant stir-
ring at 75 °C and 4 atm constant pressure of hydrogen. The products
were isolated by simple filtration and analyzed by GC.
Synlett 2004, No. 9, 1525–1528 © Thieme Stuttgart · New York