K. Boga´r, J.-E. Ba¨ckvall / Tetrahedron Letters 48 (2007) 5471–5474
5473
subjected to DKR reaction and the corresponding ace-
tates with R-configuration were obtained in 97–99%
yields with 98–99% ee’s, indicating the high efficiency
of our catalytic system.
(R)-1-Acetoxy-1-(4-trifluoromethylphenyl)ethane (entry 6).
1H NMR (CDCl3, 300 MHz) d 7.61 (d, J = 8.0 Hz, 2H),
7.46 (d, J = 8.0 Hz, 2H), 5.90 (q, J = 6.0 Hz, 1H), 2.09
(s, 3H), 1.54 (d, J = 6.5 Hz, 3H); 13C NMR (CDCl3,
75 MHz) d 170.13, 145.72, 126.29, 125.83, 125.51,
71.59, 22.24, 21.19 (one carbon is missing due to over-
lapping signals).
3. Experimental
Racemic 1-(1,2,3,4,5-pentafluorophenyl)ethanol (4) is
commercially available. Other racemic alcohols were
prepared by standard NaBH4 reduction of the corre-
sponding commercially available ketone in methanol.
Acknowledgements
This work was financially supported by the Swedish
Foundation for Strategic Research and the Swedish
Research Council.
3.1. Typical experimental procedure for DKR of second-
ary alcohols
A
solution of tBuOK (0.5 M in THF; 50 lL,
0.025 mmol) was added to mixture of RuCl-
References and notes
a
(CO)2(g5-C5Ph5) (I)8b (16 mg, 0.025 mmol), CALB
(3 mg) and Na2CO3 (53 mg, 0.5 mmol) in dry toluene
(1 mL) in a 10 mL flame-dried Schlenk tube and the
mixture was stirred for 6 min under argon at room tem-
perature. Then the substrate alcohol (0.5 mmol) was
added, and after 4 min, isopropenyl acetate (88 lL,
0.75 mmol) was added and the reaction mixture was stir-
red at room temperature. The reaction was followed by
GC. At the end of the reaction, the reaction mixture was
passed through a silica pad and concentrated. Purifica-
tion by column chromatography afforded the corre-
sponding acetates as colourless oils.
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3.2. Selected spectral data for substrates and acylated
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1-(4-Fluorophenyl)-1-propanol (entry 2). 1H NMR
(CDCl3, 400 MHz) d 7.33–7.29 (m, 2H), 7.06–7.01 (m,
2H), 4.59 (t, J = 6.6 Hz, 1H), 1.86–1.67 (m, 3H, CH2
and OH), 0.91 (t, J = 7.5 Hz, 3H); 13C NMR (CDCl3,
75 MHz) d 127.60, 127.53, 115.29, 115.08, 75.37, 32.00,
10.04.
(R)-1-Acetoxy-1-(4-fluorophenyl)propane (entry 2). 1H
NMR (CDCl3, 400 MHz) d 7.31–7.28 (m, 2H), 7.05–
7.00 (m, 2H), 5.63 (t, J = 6.9 Hz, 1H), 2.06 (s, 3H),
1.97–1.86 (m, 1H), 1.83–1.73 (m, 1H), 0.87 (t, J =
7.3 Hz, 3H); 13C NMR (CDCl3, 75 MHz) d 170.35,
163.52, 136.31, 128.36, 128.28, 115.35, 115.14, 29.23,
21.21, 9.84.
1-(3-Bromo-4-fluorophenyl)ethanol (entry 3). 1H NMR
(CDCl3, 400 MHz) d 7.59 (dd, J = 2.2, 6.6 Hz, 1H),
7.30–7.26 (m, 1H), 7.09 (t, J = 8.6 Hz, 1H). 4.87 (q,
J = 6.4 Hz, 1H), 1.78 (br s, 1H), 1.47 (d, J = 6.1 Hz,
3H); 13C NMR (CDCl3, 75 MHz) d 130.59, 125.99,
125.91, 116.48, 116.26, 69.23, 25.40.
(R)-1-Acetoxy-1-(3-bromo-4-fluorophenyl)ethane (entry 3).
1H NMR (CDCl3, 400 MHz) d 7.55 (dd, J = 2.4, 6.6 Hz,
1H), 7.26 (ddd, J = 8.4, 4.8, 2.4 Hz, 1H), 7.09 (t,
J = 8.4 Hz, 1H), 5.81 (q, J = 7.6 Hz, 1H), 2.07 (s, 3H),
1.51 (d, J = 5.6 Hz, 3H); 13C NMR (CDCl3, 75 MHz)
d 170.11, 131.31, 126.90, 126.82, 116.54, 116.320,
70.93, 22.18, 21.24.
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