M. Pucheault et al. / Tetrahedron Letters 43 (2002) 6155–6157
6157
In conclusion, we have shown that potassium organo-
trifluoroborates proved to be a good alternative in
enantioselective rhodium(I)-catalyzed conjugate addi-
tions of boron reagents to a,b-unsaturated ketone with
useful levels of enantioselectivity. These reagents, which
are more stable and easier to prepare, seemed to be
more reactive than their boronic acids analogues.
Extension of this reaction to other Michael acceptors is
currently in progress and will be reported in due course.
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Acknowledgements
M.P. thanks the Ecole Normale Supe´rieure of Paris for
a grant.
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References
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Rh(cod)2PF6 (7.0 mg, 3 mol%), and (R)-binap (10.3 mg,
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filtration on celite eluting with CH2Cl2, the solvent was
removed under reduce pressure. Chromatography purifi-
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86 mg (99% yield) of (R)-3-phenylcylohexanone (3aa) as
colourless oil with 98% e.e. (determined by HPLC analy-
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1.75–2.0 (2H, m), 2.15–2.25 (2H, m), 2.40–2.65 (4H, m),
3.1–3.3 (1H, m), 7.2–7.4 (5H, m). 13C NMR (100 MHz,
CDCl3) l: 25.4, 32.6, 41.1, 44.6, 48.8, 126.5, 126.6, 128.6,
144.3, 210.9.
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