Job/Unit: O31912
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Date: 06-03-14 11:27:54
Pages: 10
S. Cauteruccio, M. Benaglia et al.
FULL PAPER
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HPLC analysis with a Daicel Chiralcel OD-H column (hexane/
iPrOH, 99:1; 0.8 mL/min; detection: 210 nm; tR = 7.1, 7.6 min).
General Procedure for Reductive Aldol Reaction of Chalcone 9 with
Benzaldehyde: A stirred solution of catalyst (+)-2a–c (0.05 mmol,
10 mol-%) and trans-chalcone 9 (0.5 mmol, 1 equiv.) in CH2Cl2
(2 mL) was cooled to 0 °C and freshly distilled trichlorosilane
(1.75 mmol, 3.5 equiv.) was added dropwise by using a syringe. Af-
ter 15 min, freshly distilled benzaldehyde (0.60 mmol, 1.2 equiv.)
was added. After 24 h, the reaction was quenched by the addition
of saturated aqueous NaHCO3 (3 mL), then the mixture was
warmed to room temperature and stirred for 30 min. After fil-
tration through a Celite pad, the aqueous layer was extracted with
EtOAc (2ϫ 30 mL) and the combined organic layers were success-
ively washed with 15% HCl (3ϫ 20 mL), water (20 mL), saturated
aq. NaHCO3 (20 mL), brine (20 mL), and dried with Na2SO4. Af-
ter filtration and evaporation, the obtained crude product was puri-
fied by column chromatography (hexane/ethyl acetate, 95:5) to fur-
nish the aldol product 10 as a diastereomeric mixture. 1H NMR
(300 MHz, CDCl3): δ = 7. 67–6.93 (m, 15 H, syn + anti), 5.12 (d,
J = 4.6 Hz, 1 H, syn), 4.97 (dd, J = 6.4, 6.9 Hz, 1 H, anti), 4.13–
4.00 (m, 1 H, syn + anti), 3.45 (d, J = 6.9 Hz, 1 H, anti), 3.26 (br.
s, 1 H, syn), 3.19 (dd, J = 11.0, 13.7 Hz, 1 H, syn), 3.09–3.02 (m,
1 H, syn + anti), 2.91 (dd, J = 6.4, 13.8 Hz, 1 H, anti) ppm. The
enantiomeric excess was determined by chiral HPLC analysis with
a Daicel Chiralcel OD-H column (hexane/iPrOH, 95:5; 1.0 mL/min
flow rate; detection: 225 nm; tR = 14.5, 16.1, 20.0, 22.4 min).
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1
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Acknowledgments
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c) M. Sámal, J. Misˇek, I. G. Stará, I. Starý, Collect. Czech.
M. B. and E. L. thank the Ministero dell’Università e della Ricerca
(MIUR), Roma, and the University of Milan (UNIMI) within the
national project “Nuovi metodi catalitici stereoselettivi e sintesi
stereoselettiva di molecole funzionali” (PRIN 2009). M. B. also
acknowledges the European COST Action ORCA – CM0905-
Organocatalysis. S. C. acknowledges UNIMI for a postdoctoral fel-
lowship. D. D., A. G., and M. O. acknowledge UNIMI for PhD
fellowships.
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