H. Brunner et al. / Tetrahedron: Asymmetry 12 (2001) 497–499
499
for 24 h. The solution was cooled to 25°C, and 1 (440
mg, 2.5 mmol) was added. After stirring at 25°C for 4
h the solvent was removed in vacuo and the sample was
purified by bulb-to-bulb distillation. The product was
obtained using a Rt-bDEX cst column (length 30 m,
lumen 0.32 mm, film thickness 0.25 mm). Retention
times: 27.5 min (R)-(−)-4, 28.8 min (S)-(+)-4, 37.0 min
3. Assignment of peaks was based on the optical rota-
tion of enantiomerically enriched samples.
obtained as a colourless oil in quantitative yield (bp
1
1
1
2
10°C/0.1 hPa). H NMR (250 MHz, CDCl ): 1: l=
3
.67–1.82 (m, 1H, CH ), 1.92–2.08 (m, 1H, CH ), 2.24–
1
2
2
3.8. Enantiomer analysis of 3/4 by H NMR
.37 (m, 2H, CH ), 2.74–2.85 (m, 2H, CH ), 7.35–7.58
2
2
(
m, 3H, CHarom), 8.00–8.05 (m, 2H, CHarom). 2: l=
1
H NMR analysis using chiral shift reagents confirmed
1
2
1
.70–1.90 (m, 1H, CH ), 1.95–2.11 (m, 1H, CH ), 2.13–
2
2
the GC results. This was necessary to exclude thermal
rearrangement due to the high oven temperatures.
.26 (m, 1H, CH ), 2.35–2.50 (m, 3H, CH ), 3.33 (s,
2
2
H, OH), 7.32–7.37 (m, 5H, CHarom).
7
Using trimethylsilylimidazole as a derivatising agent,
the trimethylsilyl derivatives both of 3 and 4 were
formed. After addition of a four-fold excess of (S)-(+)-
3
.4. GC analysis of 1 and 2
1
-(9%-anthryl)-2,2,2-trifluoroethanol the OSi(CH ) sin-
3 3
Hewlett–Packard 5890 II, split injector (125°C), FID
detector (260°C), Spectra-Physics SP 4270 integrator,
oven temperature initially 30°C, then heating to 150°C
at max. rate, hydrogen as carrier gas, solvent CH Cl .
glet of 4 split and integration was possible. Chemical
shifts of the OSi(CH3)3 protons: l=−0.065 ppm 3,
−0.079 ppm (R)-(−)-4, −0.085 ppm (S)-(+)-4.
2
2
Baseline separation was obtained using a Rt-bDEX cst
3
.9. Attempted synthesis of 2-hydroxy-2-phenylcyclo-
column (length 30 m, lumen 0.32 mm, film thickness
heptanone 6
0
.25 mm). Retention times: 14.5 min (−)-2, 15.2 min
(
+)-2, 16.2 min 1. Assignment of the peaks was based
Commercially available 1-benzoylcyclohexanol 5 (2.04
g, 10.0 mmol), NiCl2 (26.0 mg, 0.20 mmol) and
TMEDA (46.5 mg, 59.6 ml, 0.40 mmol) were heated to
on the optical rotation of enantiomerically enriched
samples.
1
30°C for 96 h. Bulb-to-bulb distillation (130°C/0.1
3.5. 1-Benzoylcyclopentanol 3
1
hPa) gave the unchanged starting material 5. H NMR
(
7
250 MHz, CDCl ): 5: l=1.63–2.05 (m, 10H, CH ),
3
2
1
-Benzoylcyclopentanol, 3, was synthesised according
.40–7.57 (m, 3H, CHarom), 7.99–8.03 (m, 2H, CHarom).
6
to the literature and stored at −40°C.
3.6. 2-Hydroxy-2-phenylcyclohexanone 4
Acknowledgements
The catalytically active species was prepared as above.
After 24 h the substrate 3 (476 mg, 2.5 mmol) was
added to the refluxing methanol solution. After stirring
under reflux for 120 h the solvent was removed. Bulb-
to-bulb distillation gave the product 4 as a colourless
oil (A quantitative mass was obtained which was a
We thank the DFG and the CNRS for support of our
trans-national CERC3 project.
mixture of 4 (96%) and 3 (4%) as detected by GC
References
1
analysis). H NMR (250 MHz, CDCl ): 3, l=1.85–2.10
3
(
m, 6H, CH ), 2.30–2.44 (m, 2H, CH ), 3.75 (s, 1H,
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2
2
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3
.7. GC analysis of 3/4
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Hewlett–Packard 5890 II, split injector (230°C), FID
detector (260°C), Spectra-Physics SP 4270 integrator,
oven temperature 130°C for 32 min, then heat rate of
8
°C/min to 170°C, subsequently 170°C, hydrogen as
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2
2
.