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Cobalt Carbonyl-Based Catalyst for Hydrosilylation of Carboxamides
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Interestingly, the present transformation catalysed
by a cobalt complex is quite comparable to the iron-
catalysed hydrosilylation reaction: both systems are
efficient with inexpensive siloxanes and can be acti-
vated under UV irradiation or thermal conditions.
The main difference lies in the lower loading of
cobalt (0.5 mol%) compared to iron carbonyl com-
plexes (typically 5 mol%).
In conclusion, we have demonstrated that the com-
mercially available Co2(CO)8 complex can be used in
low catalytic loading for the chemoselective reduction
of tertiary amides in the presence of the inexpensive
PMHS as the reductant.
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Experimental Section
Typical Procedure for Cobalt-Catalysed
Hydrosilylation of Amides (Table 2)
A 10-mL oven-dried Schlenk tube containing a stirring bar,
was charged with [Co2(CO)8] (1.7 mg, 0.5 mol%). After
purging with argon (argon-vacuum three cycles), the amide
derivative (1 mmol) was added followed by PMHS (130 mL,
2.2 mmol) and toluene (2 mL). The reaction mixture was
stirred in a preheated oil bath at 1008C for 3 h. Then 1 mL
of MeOH was added followed by 1 mL of 2M NaOH aque-
ous solution with vigorous stirring. The reaction mixture was
further stirred for 1 hour at room temperature and was ex-
tracted with diethyl ether (2ꢂ10 mL). The combined organic
layers were washed with brine (3ꢂ10 mL), dried over anhy-
drous MgSO4, filtered and concentrated under vacuum. The
conversion was determined by 1H NMR. The residue was
then purified by silica gel column chromatography using
ethyl acetate-petroleum ether mixture (0 to 10%) to afford
the desired amine.
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Acknowledgements
We are grateful to the CNRS, the University of Rennes 1, and
the Ministꢀre de l’Enseignement Supꢁrieur et de la Recherche
for support, and the “Rꢁgion Bretagne” for a post-doctoral
grant “CREATE” to TD.
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References
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