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Fluka). The reactions were monitored by TLC carried out on pre-
coated (Merck TLC silica gel 60 F254) aluminium plates by using UV
light as visualising agent and cerium molybdate solution as devel-
tion and solvent removal under reduced pressure, the residue ob-
tained was purified by flash chromatography with an eluent gradi-
ent from ethyl acetate/hexane (9:1) to methanol/ethyl acetate (1:9).
oping agent. Flash column chromatography was performed on sil- The desired ketone 5 was obtained in 75 % yield (1.03 g) with simi-
[
10] 1
ica gel 60 (Merck, 0.040–0.063 mm). NMR spectra were recorded lar spectroscopic data as previously reported.
H NMR (D O,
2
with a Varian Mercury 300 MHz spectrometer using CDCl3,
300 MHz): δ = 4.83 (s, 3 H), 4.29 (ddd, J = 6.3, 3.7, 2.9 Hz, 1 H), 4.15
(td, J = 8.2, 5.3 Hz, 1 H), 3.97 (dd, J = 7.8, 2.8 Hz, 1 H), 2.83–2.80 (m,
[
D ]DMSO or D O as solvent and calibrated by using tetramethyl-
6 2
silane as internal standard. Chemical shifts are reported in ppm 1 H), 2.78–2.75 (m, 1 H), 2.65–2.50 (m, 2 H) ppm. 13C NMR (D O,
2
1
relative to TMS and coupling constants are reported in Hz. H NMR
yields were determined by adding a known amount of bromo-
benzene to the reaction mixture after work-up.
75 MHz): δ = 212.8, 73.0, 68.7, 45.7 ppm.
4-Methoxyphenol (6): Ketone 5 (0.5 mmol) was dissolved in meth-
anol (1 mL) and dispersed in toluene (10 mL) in a round-bottomed
flask equipped with a magnetic stirrer bar. Amberlyst 15 (dry,
384 mg) was added and the mixture stirred at 100 °C until disap-
pearance of the starting material, as judged by TLC (1.5 h). After
Hydroquinone (2): Quinic acid (0.5 mmol) was added to a suspen-
sion of Amberlyst-15 (dry, 0.38 g) in toluene (10 mL) in a round-
bottomed flask equipped with a magnetic stirrer bar and condenser
open to the air. The mixture was heated at 100 °C for 24 h. After cooling to room temperature, methanol (5 mL) was added, the mix-
cooling to room temperature methanol (5 mL) was added and the
mixture stirred vigorously for 5 min. The mixture was filtered and
the solid residue re-suspended in methanol (20 mL) and stirred for
an additional 5 min. After filtration and washing with more meth-
ture filtered and the solvent removed under reduced pressure. The
residue was purified by flash chromatography with gradient elution
with ethyl acetate/hexane (1:9 to 1:1), to afford 42 % (23 mg) of
hydroquinone (2) and 37 % (23 mg) of 6 with similar spectroscopic
[
24] 1
anol (10 mL), the solvents were removed under reduced pressure.
data as previously reported.
H NMR (CDCl , 300 MHz): δ = 6.78
3
1
13
The residue was either dissolved in [D ]DMSO for H NMR yield
(d, J = 1.8 Hz, 4 H), 4.93 (br. s., 1 H), 3.77 (s, 3 H) ppm. C NMR
6
determination (72 %) or purified by flash chromatography with tolu-
(CDCl , 75 MHz): δ = 153.6, 149.4, 116.0, 114.8, 55.8 ppm.
3
ene/ethyl acetate (3:1) to afford pure hydroquinone (39 mg, 71 %
4
,5-Dihydroxycyclohex-2-en-1-one (7): Amberlyst-15 (dry, 0.38 g)
was added to a solution of ketone 5 (1 mmol) in 1,4-dioxane
10 mL) and the mixture stirred at 100 °C for 5 min. After cooling
1
yield) with similar spectroscopic data as commercial samples.
H
C
13
NMR ([D ]DMSO, 300 MHz): δ = 8.64 (s, 2 H), 6.55 (s, 4 H) ppm.
6
(
NMR ([D ]DMSO, 75 MHz): δ = 149.8, 115.8 ppm.
6
to room temperature the mixture was filtered and the solvent re-
moved under reduced pressure. The residue was purified by flash
chromatography with eluent gradient from ethyl acetate/hexane
(4:1) to methanol/ethyl acetate (1:9) to afford 20 % (20 mg) of hy-
Bis(4-hydroxyphenyl) Ether (3): Hydroquinone (1.0 mmol) was
added to a suspension of Amberlyst-15 (dry, 0.77 g) in toluene
(20 mL) in a round-bottomed flask equipped with a magnetic stirrer
bar and condenser. The mixture was heated at 100 °C for 6 d. After droquinone (2) and 25 % (31 mg) of 7 in a cis/trans ratio of 1:4, as
1
cooling to room temperature, methanol (10 mL) was added and the
mixture stirred vigorously for 5 min. The mixture was filtered and
the solid residue re-suspended in methanol (40 mL) and stirred for
determined by H NMR spectroscopy and comparison with previous
[
10] 1
reports.
H NMR (D O, 300 MHz): δ = 6.96 (dd, J = 10.1, 2.2 Hz,
1 H), 6.92–6.87 (m, 0.2 H), 6.73–6.72 (m, 0.2 H), 6.06 (dd, J = 2.2,
2
an additional 5 min. After filtration and washing with more meth- 1.0 Hz, 0.2 H), 6.03–5.98 (m, 1 H), 4.64–4.61 (m, 0.2 H), 4.39–4.30 (m,
anol (20 mL), the solvents were removed under reduced pressure.
The residue was purified by preparative TLC with toluene/ethyl
1.2 H), 3.99–3.91 (m, 1 H), 2.78–2.76 (m, 0.5 H), 2.73–2.71 (m, 1 H),
2.68 (dd, J = 5.1, 1.0 Hz, 0.2 H), 2.55–2.46 (m, 1.3 H) ppm. C NMR
1
3
acetate (3:1) to afford pure 3 (49 mg, 48 %) with similar spectro- (D O, 75 MHz): δ = 204.8, 204.4, 156.2, 154.2, 151.8, 131.6, 131.5,
2
[22] 1
scopic data as previously reported.
H NMR (CDCl , 300 MHz):
119.2, 74.4, 74.3, 72.5, 70.3, 68.8, 63.3, 57.8, 46.5, 45.7 ppm.
3
1
3
δ = 6.70–6.83 (m, 8 H) ppm. C NMR (CDCl , 75 MHz): δ = 151.9,
3
1
50.8, 120.1, 119.4, 115.9 ppm.
Acknowledgments
N. R. C. acknowledges the Academy of Finland for an academy
Quino-1,5-lactone (4): Amberlyst-15 (dry, 0.69 g) was added to a
suspension of quinic acid (3 mmol) in acetonitrile (150 mL) and the
mixture stirred at 50 °C for 24 h. After cooling, the reaction mixture research fellowship (decision number 287954). Dr. Alexandre Ef-
was filtered through Celite and washed with methanol. Solvent re- imov is acknowledged for valuable discussions of the NMR
moval under reduced pressure yielded the desired lactone 4 in spectra and Dr. Henrik Tolvanen for facilitating the use of the
quantitative yield (0.52 g) with similar spectroscopic data as previ-
grinder and sieve.
ously reported.[
23] 1
H NMR ([D ]DMSO, 300 MHz): δ = 5.90 (s, 1 H),
6
5
1
2
1
6
.24 (d, J = 3.8 Hz, 1 H), 4.84 (d, J = 6.7 Hz, 1 H), 4.61 (t, J = 5.3 Hz,
H), 3.81 (d, J = 4.1 Hz, 1 H), 3.49 (dd, J = 11.0, 4.8 Hz, 1 H), 2.27–
Keywords: Sustainable chemistry · Heterogeneous
catalysis · Natural products · Cyclitols
.24 (m, 1 H), 2.13–2.07 (m, 1 H), 1.87–1.82 (m, 1 H), 1.75–1.66 (m,
H) ppm. 13C NMR ([D ]DMSO, 75 MHz): δ = 177.8, 76.0, 71.6, 65.6,
6
5.3, 39.4, 36.8 ppm.
[
1] C. H. Christensen, J. Rass-Hansen, C. C. Marsden, E. Taarning, K. Egeblad,
(
3R,5R)-3,4,5-Trihydroxycyclohexanone (5): Prepared according
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[2] P. Gallezot, Chem. Soc. Rev. 2012, 41, 1538–1558.
3] F. W. Lichtenthaler, Ullmann's Encyclopedia of Industrial Chemistry, Wiley-
VCH, Weinheim, Germany, 2000.
4] J. ten Dam, U. Hanefeld, ChemSusChem 2011, 4, 1017–1034.
5] F. Cherubini, A. H. Strømman, Biofuels Bioprod. Bioref. 2011, 5, 548–561.
6] a) L. Krumenacker, M. Costantini, P. Pontal, J. Sentenac, in Kirk-Othmer
Encyclopedia of Chemical Technology, 5th ed., John Wiley & Sons, Inc.,
Hoboken, New Jersey, 2000; b) P. M. Hudnall, Ullmann's Encyclopedia of
Industrial Chemistry, Wiley-VCH, Weinheim, Germany, 2000.
[10]
to a previously reported procedure. A 14 % aqueous NaOCl solu-
tion (30 mmol) and H SO (8 mmol) were added dropwise to a
[
2
4
stirred solution of quinic acid (10 mmol) in water (7 mL) over
0 min. The reaction was stirred at room temperature for 2.5 h. The
[
[
[
3
reaction was then quenched with isopropanol (30 mmol) and
stirred for 30 min. After pH neutralisation with an aqueous satu-
rated solution of Na CO , the solvent was removed under reduced
2
3
pressure. The obtained residue was re-suspended in acetone
55 mL) and left to stir overnight at room temperature. After filtra-
(
[7] A. Woskresensky, Ann. Pharm. 1838, 27, 257–270.
Eur. J. Org. Chem. 0000, 0–0
www.eurjoc.org
5
© 0000 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim