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reaction in the aldol formation compared to that when isopropoxide
is applied as the base catalyst.
In conclusion, we present tetrahedral sodium triisopropyl
3,5-difluorophenylboronate (4) as a base, which can catalyse the
aldol reaction. It is soluble in organic media, allowing the use
of a substrate, acetone, as solvent. The reaction proceeds
rapidly, with high conversion and good selectivity towards
b-hydroxyketone. The tetrahedral boronate acts as a base,
suitable to form boron-enolate with acetone, but is not able
to dehydrate the formed aldol.
This research has been performed within the framework of the
CatchBio program. The authors gratefully acknowledge the support
of the Smart Mix Program of the Dutch Ministry of Economic
Affairs and the Dutch Ministry of Education, Culture and Science.
The authors are thankful to L. Panella (DSM), P. Alsters (DSM), J. G.
de Vries (DSM), B. Kaptein (DSM), G. Kemperman (MSD) for fruitful
discussions, and S.A. Kulkarni (TU Delft, P&E/IRS) for the Raman
measurements.
Notes and references
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Scheme 2 Proposed mechanism for the aldol reaction catalysed by tetrahedral
boronate salt 4, including the elimination reaction in the presence of a strong
nucleophilic base, NaOiPr.
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c
This journal is The Royal Society of Chemistry 2013
Chem. Commun., 2013, 49, 361--363 363