An efficient approach to either enantiomer of trans-cyclohex-2-ene-1,4-diol

Article abstract of DOI:10.1016/j.tetasy.2004.02.003

(1S,4S)-Cyclohex-2-ene-1,4-diol has been synthesised starting from a chiral p-benzoquinone equivalent. The sequence can be equally applied to the preparation of the (1R,4R)-enantiomer of the target diol.

Full text of DOI:10.1016/j.tetasy.2004.02.003

Tetrahedron:
Asymmetry
Tetrahedron: Asymmetry 15 (2004) 1151–1155
An efficient approach to either enantiomer
of trans-cyclohex-2-ene-1,4-diol
*
ꢀ
Ramon Alibes, Pedro de March, Marta Figueredo, Josep Font and Georgina Marjanet
Departament de Quꢀımica, Universitat Autꢁonoma de Barcelona, 08193 Bellaterra, Spain
Received 19 January 2004; accepted 4 February 2004
Abstract—(1S,4S)-Cyclohex-2-ene-1,4-diol has been synthesised starting from a chiral p-benzoquinone equivalent. The sequence can
be equally applied to the preparation of the (1R,4R)-enantiomer of the target diol.
ꢀ 2004 Elsevier Ltd. All rights reserved.
1. Introduction
70% ee. Comparison with the major oxidation product
along with mechanistic considerations led the authors to
assign the (1R,4R) configuration to the dextrorotatory
enantiomer of trans-1. On the other hand, a lipase-based
protocol developed for desymmetrisation of the diace-
tate of cis-1 gave access to an alternative chiral equiva-
lent of trans-1, which has been used as an intermediate
for the synthesis of petasins8 and cyclohexane prosta-
noids.9
There are a large number of natural compounds pos-
sessing a polysubstituted cyclohexane unit as a funda-
mental structural part. Among them, polyoxygenated
derivatives such as conduritols,1 conduramines,2 inosi-
tols,3 gabosines4 and several epoxides5 are particularly
attractive targets because of their diverse biological
activities and the synthetic challenge of binding oxygen
atoms to a carbocycle in a regio- and stereocontrolled
€
fashion. In 1984 Backvall et al. reported the stereo-
In previous work, we had prepared a series of chiral
derivatives of p-benzoquinone, such as 210;11 and 3,11;12
and explored their utility as synthetic precursors of more
complex target cyclohexanes.13–15 As a result of these
studies, we developed the first syntheses of (+)-rengyol-
one, 4, and (+)- and ())-menisdaurilide, 5,16 along with
new synthetic approaches to (R)- and (S)-4-hydroxy-2-
cyclohexenone, 6.17 In connection with our previous
work, we herein report the synthesis of trans-1, starting
from 3, a masked p-benzoquinone in which one of each
selective synthesis of both diastereomers of cyclohex-2-
ene-1,4-diol, cis- and ( )-trans-1 (Fig. 1), through a
palladium-catalysed 1,4-diacetoxylation of 1,3-cyclo-
hexadiene.6 Nowadays, the racemate of trans-1 is com-
mercially available, but only one procedure has been
reported to obtain nonracemic trans-1, by a chloroper-
oxidase-catalysed oxidation of cyclohexa-1,3-diene
using tert-butylhydroperoxide as the terminal oxidant.7
This procedure furnished (+)-trans-1 in 34% yield and
O
O
O
OH
OH
HO
O
O
H
H
SPh
O
O
O
O
O
OH
OH
O
Ph
Ph
2
4
5
6
trans-1
3
Figure 1.
* Corresponding author. Tel.: +34-93-5811853; fax: +34-93-5811265; e-mail: marta.figueredo@uab.es
0957-4166/$ - see front matter ꢀ 2004 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tetasy.2004.02.003

1152
R. Alibꢀes et al. / Tetrahedron: Asymmetry 15 (2004) 1151–1155
OH
OH
OH
OH
O
OH
(1S,4S)-1
SPh
SPh
SPh
SPh
O
O
O
O
O
OH
OH
(R)-3
7
8
9
OH
(1R,4R)-1
Scheme 1.
pair of equivalent functional groups has been differen-
tiated.
(TBDMS-Im) in dichloromethane at room temperature
for several days gave the expected silyl ether 10 (Scheme
2) in 83% yield. Various standard procedures for the
hydrolysis of the dioxolane were also unsuccessful with
ketone 11 finally being obtained in 75% yield by treat-
ment of 10 with montmorillonite K-10 in dichlorome-
thane.16;18 Due to the configurational instability of the
a-carbonyl stereogenic centre, the initially formed iso-
mer cis-11 slowly became contaminated with its trans
2. Results and discussion
The racemate of compound 3 is easily available on
multi-gram scale with its resolution being effectively
performed by liquid chromatography on cellulose tri-
acetate.11;12 The reduction of 3 with NaBH4 exclusively
gives the cis-alcohol 7, which when hydrolysed furnishes
the hydroxyketone 8 in excellent overall yield16 (Scheme
1). We initially envisaged the conversion of 8 into trans-
1 by consecutive reduction of the ketone and thioether
functions. According to this plan, the overall transfor-
mation starting from (R)-3 would provide the (1S,4S)-
enantiomer of 1. Alternatively, the double bond of diol 9
could be hydrogenated and a new double bond gener-
ated by oxidation–pyrolysis of the sulfur moiety,
affording the opposite antipode (1R,4R)-1. To test the
effectiveness of the approach, we first undertook the
synthesis starting from racemic 8.
1
diastereomer. In the H NMR spectrum of cis-11, the
proton at the epimerisable centre displayed a signal at
d 3.79 with coupling constants of 13.2and 4.4 Hz in
agreement with a pseudoaxial orientation, while for
trans-11 the corresponding signal at d 3.97 showed two
similar vicinal coupling constants of around 4.5 Hz and
a long distance coupling of 1.0 Hz, in agreement with its
pseudoequatorial location. The use of a mixture of
epimers in the next step was not detrimental for the
synthesis. The reduction of 11 with DIBAL-H in THF at
)78 ꢁC furnished a mixture of diols 12 and 13, in which
the former isomer was strongly predominant. NOE
experiments demonstrated that 12 and 13 were epimers
at C-6, but both presented the desired trans relationship
between the hydroxy and silyloxy groups. Thus, pre-
saturation of the signal of H-4 (d 4.38 for 12 and d 4.34
for 13) caused enhancement of the signal of H-6 for
compound 12 (d 2.97) but not for 13 (d 3.79), while
irradiation of the H-1 signal (d 4.10 for 12 and d 4.13 for
13) produced enhancement of the signal corresponding
to H-6 only for isomer 13. Occasionally, trace amounts
of the all-cis isomer of 12 and 13 were also detected.
Desulfuration of 12 and 13 was accomplished by treat-
ment with SnBu3H in refluxing toluene in the presence
of 2,20-azobisisobutyronitrile (AIBN). We were unable
to let this reaction go to completion, but the conditions
could be adjusted to obtain the desulfuration product 14
in a fair yield (67%, 86% over converted substrate) along
In practice, all attempts to perform the reduction of
ketone 8 with a variety of hydrides and conditions gave
poor stereoselectivity. Moreover, decomposition of the
formed diols was frequently observed before complete
conversion of the substrate. Protection of the hydroxyl
group of 8 prior to the reduction of the ketone proved
equally ineffective, leading consistently to complex
mixtures of unidentified products. This problem could
be overcome by protecting the alcohol in 7 before the
ketal hydrolysis. Treatment of 7 with different silyl
chlorides in basic media caused decomposition, but
the reaction with tert-butyldimethylsilylimidazole
OTBDMS
OTBDMS
OTBDMS
4
OTBDMS
OTBDMS
a
b
c
d
e
7
trans-1
+
6
SPh
SPh
SPh
SPh
OH
1
OH
O
O
O
OH
12
10
11
13
14
Scheme 2. Reagents and conditions: (a) TBDMS-Im, CH2Cl2, rt, 5 days, 83%; (b) montmorillonite K-10, CH2Cl2, rt, 18 h, 75%; (c) DIBAL-H, THF,
)78 ꢁC, 2.5 h, 72%; (d) SnBu3H, AIBN, toluene, D, 5 h, 86%; (e) Bu4NF, THF, rt, 20 h, 78%.

R. Alibꢀes et al. / Tetrahedron: Asymmetry 15 (2004) 1151–1155
1153
with the unreacted starting material, which could be
easily recovered. The overall sequence from 3 to 14 was
38%. Compound 14 is a monoprotected derivative of the
target diol trans-1 and would formally result from dif-
ferentiation of the two initially equivalent alcohols,
making it especially attractive for synthetic purposes.
Finally, treatment of 14 with tetrabutylammonium
fluoride in THF produced trans-1 in 78% yield.
from (R)-3 in 85% yield following the procedure previ-
ously described for the racemate.17
4.3. cis-8-(tert-Butyldimethylsilyloxy)-10-phenylthio-1,4-
dioxaspiro[4.5]dec-6-ene, 10
To a stirred solution of 7 (2.00 g, 7.56 mmol) in CH2Cl2
(60 mL) at 0 ꢁC under nitrogen, TBDMS-Im (2.35 mL,
12.10 mmol) was slowly added (5 min), the cooling bath
removed and the mixture stirred at room temperature
for 5 days. Water (5 mL) was then added and the mix-
ture slightly acidified with 4% HCl. The organic layer
was separated and the aqueous layer extracted with
CH2Cl2 (3 · 30 mL). The combined organic extracts
were washed, dried and concentrated under vacuum.
Purification of the oily residue (2.82 g) by flash chro-
matography (diethyl ether/hexane, 1:5) furnished com-
pound 10 (2.38 g, 6.29 mmol, 83%) as a white solid: mp
35–37 ꢁC; IR (KBr) 3069, 2955, 2884, 1584, 1472, 1386,
When the complete sequence was repeated starting from
(8S,10R)-7, readily available by NaBH4 reduction of
20
D
(R)-3,17 the diol (1S,4S)-1, ½aŠ ¼ À112( c 0.25, CHCl3),
was obtained. Analysis by CHPLC showed an ee of
95%.
3. Conclusion
In summary, starting with the p-benzoquinone equiva-
lent 3, a procedure has been set up for the synthesis of
trans-cyclohex-2-ene-1,4-diol, trans-1, suitable for the
preparation of either enantiomer of the diol. Applica-
tion of the sequence to (R)-3 furnished the levorotatory
antipode (1S,4S)-1, confirming the (1R,4R)-configura-
tion tentatively assigned to the main enantiomer of
trans-1 obtained by a chloroperoxidase-catalysed oxi-
dation of cyclohexa-1,3-diene.7 Taking into account that
any antipode of 3 can be re-equilibrated to the racemate
by a base catalysed process involving elimination/con-
jugate addition of thiophenol, racemic 3 can be con-
verted into either enantiomer of trans-1.
1
1248, 1154, 1086 cmÀ1; H NMR (250 MHz) d 7.46 (m,
2H), 7.22 (m, 3H), 5.76 (dt, J ¼ 10:2, 1.9 Hz, 1H), 5.57
(dd, J ¼ 10:2, 2.0 Hz, 1H), 4.25 (m, 1H), 4.10 (m, 4H),
3.40 (dd, J ¼ 14:0, 3.2 Hz, 1H), 2.28 (dddd, J ¼ 12:5,
5.7, 3.2, 1.8 Hz, 1H), 2.05 (ddd, J ¼ 14:0, 12.5, 9.8 Hz,
1H), 0.83 (s, 9H), 0.02(s, 3H), 0.01 (s, 3H); 13C NMR
(62.5 MHz) d 136.1, 135.6, 130.9, 128.8, 127.7, 126.5,
106.1, 68.0, 66.4, 66.1, 52.7, 39.7, 25.7, 18.0, )4.5, )4.7;
MS m=z 378 (Mþ, 0.1), 269 (7), 242 (100), 75 (63), 73
(52). Anal. Calcd for C20H30O3SSi: C, 63.45; H, 7.99; S,
8.47. Found: C, 63.42; H, 7.99; S, 8.14.
The same procedure starting from (8S,10R)-7 gave
20
D
(CHPLC, hexane/2-propanol, 90:10).
(8S,10R)-10, ½aŠ ¼ À56 (c 0.85, CHCl3), ee 100%
4. Experimental
4.1. General
4.4. 4-(tert-Butyldimethylsilyloxy)-6-phenylthiocyclohex-
2-enone, 11
Reaction mixtures were stirred magnetically. The
organic extracts were dried over anhydrous magnesium
sulfate. Reaction solutions were concentrated using a
rotary evaporator at 5–10 Torr. Flash chromatography
was performed using Merck silica gel (230–400 mesh).
Infrared spectra were recorded on an IR-FT Perkin
Elmer 2000 spectrophotometer. 1H and 13C NMR
spectra were recorded on Brucker AC-250-WB or AM-
400-WB instruments at 250 or 400 MHz and 62.5 or
100 MHz, respectively, in CDCl3 solutions. Tetrameth-
ylsilane or CHCl3 were used as internal standards for 1H
and 13C NMR spectra. Mass spectra were performed on
a Hewlett–Packard 5989A at 70 eV or on a Brucker Esi-
it instruments; only peaks with higher intensity than
20% are reported, unless they belong to molecular ions
or to significant fragments. Enantiomeric excesses (eeÕs)
were determined by CHPLC analyses using a Daicel
Chiracel OD column (4.6 · 250 mm).
A mixture of 10 (914 mg, 2.41 mmol) and montmoril-
lonite K-10 (3.2g) in CH 2Cl2 (28 mL) was stirred at
room temperature for 18 h. The mixture was filtered and
the solvent removed under vacuum. Flash chromato-
graphy of the crude material (759 mg) using diethyl
ether/hexane (1:10) as eluent afforded cis-11 (601 mg,
1.80 mmol, 75%) as oil: IR (neat) 3059, 2954, 2929, 2857,
1685, 1472, 1253, 1097 cmÀ1; 1H NMR (250 MHz) d 7.42
(m, 2H), 7.27 (m, 3H), 6.76 (dt, J ¼ 10:2, 1.9 Hz, 1H),
5.98 (dd, J ¼ 10:2, 2.0 Hz, 1H), 4.52 (ddt, J ¼ 9:6, 4.7,
2.0 Hz, 1H), 3.79 (dd, J ¼ 13:2, 4.4 Hz, 1H), 2.42 (dddd,
J ¼ 12:9, 4.7, 4.4, 1.7 Hz, 1H), 2.06 (ddd, J ¼ 13:2, 12.9,
9.6 Hz, 1H), 0.84 (s, 9H), 0.04 (s, 3H), 0.02(s, 3H); 13C
NMR (62.5 MHz) d 194.5, 153.7, 132.9, 128.9, 127.7,
67.6, 52.3, 40.4, 25.7, 18.0, )4.6, )4.8; MS m=z 334 (Mþ,
0.2), 225 (20), 224 (22), 168 (35), 167 (100), 75 (31), 73
(36). Anal. Calcd for C18H26O2SSi: C, 64.62; H, 7.83; S,
9.58. Found: C, 64.66; H, 7.73; S, 9.13.
4.2. (8S,10R)-10-Phenylthio-1,4-dioxaspiro[4.5]dec-6-en-
8-ol, (8S,10R)-7
Compound cis-11 epimerises slowly to its isomer trans-
1
11: H NMR (250 MHz) d 7.42 (m, 2H), 7.29 (m, 3H),
20
Compound (8S,10R)-7, ½aŠ ¼ À15 (c 0.95, CHCl3), ee
6.76 (ddd, J ¼ 10:2, 2.7, 1.2 Hz, 1H), 5.91 (ddd,
D
100% (CHPLC, hexane/2-propanol, 95:5), was prepared
J ¼ 10:2, 1.8, 1.0 Hz, 1H), 4.73 (dddd, J ¼ 10:0, 3.2, 2.7,

1154
R. Alibꢀes et al. / Tetrahedron: Asymmetry 15 (2004) 1151–1155
1.8 Hz, 1H), 3.97 (td, J ¼ 4:5, 1.0 Hz, 1H), 2.35 (com-
plex, 2H), 0.88 (s, 9H), 0.08 (s, 3H), 0.07 (s, 3H); 13C
NMR (62.5 MHz) d 193.8, 152.1, 133.4, 127.8, 126.9,
64.5, 50.7, 38.7, 25.7, 18.0, )4.6, )4.8.
4.6. trans-4-(tert-Butyldimethylsilyloxy)cyclohex-2-enol,
14
To a stirred solution of a mixture of 12 and 13 (200 mg,
0.59 mmol) and AIBN (1.0 mg, 0.006 mmol) in anhy-
drous toluene (6 mL) under nitrogen at the reflux tem-
perature, SnBu3H (1.46 mL, 5.94 mmol) was added
dropwise. A solution of AIBN (300 mg, 1.83 mmol) in
anhydrous toluene (12mL) was added to the reaction
mixture in 0.25 mL portions every 5 min and, after the
last addition, heating was prolonged 1 h further. The
solvent was evaporated under vacuum and purification
of the residue (200 mg) by flash chromatography (hex-
ane/ethyl acetate, 12:1) yielded the starting materials 12
and 13 (45 mg, 0.13 mmol, 22% recovered) and 14
(91 mg, 0.40 mmol, 67%, 86% over unrecovered sub-
strate): colourless oil; IR (neat) 3338, 3029, 2952, 2929,
2857, 1472, 1388, 1257, 1084 cmÀ1; 1H NMR (250 MHz)
d 5.71 (m, 2H), 4.24 (m, 2H), 2.10 (m, 1H), 1.87 (m, 1H),
1.52(m, 1H), 1.44 (m, 1H), 0.87 (s, 9H), 0.06 (s, 3H),
0.05 (s, 3H); 13C NMR (62.5 MHz) d 133.8, 131.7, 67.0,
66.6, 30.9, 30.4, 25.8, 18.7, )4.5, )4.6; MS m=z 251
([M+Na]þ, 100). Anal. Calcd for C12H24O2Si: C, 63.10;
H, 10.59. Found: C, 63.09; H, 10.65.
The same procedure starting from (8S,10R)-10 gave a
mixture of (4S,6R)-11 and (4S,6S)-11.
4.5. Reduction of 11: (1RS,4SR,6RS)-, 12, and
(1RS,4SR,6SR)-4-(tert-butyldimethylsilyloxy)-6-phenyl-
thiocyclohex-2-enol, 13
To a stirred solution of 11 (1.54 g, 4.6 mmol) in anhy-
drous THF (62mL) at )78 ꢁC under nitrogen, a solution
of DIBAL-H in THF (1 M, 18.4 mL, 18.4 mmol) was
added. After stirring the mixture at )78 ꢁC for 2.5 h,
MeOH (62mL) was added and stirring was continued
for 1 h, while warming to room temperature. The mix-
ture was then filtered through Celiteꢂ and the solvent
removed under vacuum. The oily residue (1.12g,
3.34 mmol, 72%) was identified as a mixture of 12 and
13, which was used in the next step without further
purification. For characterisation purposes, an analyti-
cal sample of the major isomer 12 was isolated by
repeated flash chromatography: IR (neat) 3401, 3033,
2954, 2856, 1472, 1253, 1087 cmÀ1; 1H NMR (250 MHz)
d 7.45 (m, 2H), 7.31 (m, 3H), 5.71 (dt, J ¼ 10:2, 1.7 Hz,
1H), 5.62(dq, J ¼ 10:2, 1.8 Hz, 1H), 4.38 (m, 1H), 4.10
(m, 1H), 2.97 (ddd, J ¼ 13:6, 9.1, 2.9 Hz, 1H), 2.68
(broad, 1H), 2.28 (dddd, J ¼ 12:7, 5.5, 2.9, 1.8 Hz, 1H),
1.67 (ddd, J ¼ 13:6, 12.7, 9.0 Hz, 1H), 0.85 (s, 9H), 0.04
(s, 3H), 0.03 (s, 3H); 13C NMR (62.5 MHz) d 134.3,
133.4, 129.5, 128.1, 70.0, 68.2, 51.6, 39.4, 25.8, 18.1,
)4.6, )4.7; MS m=z 279 ([M)tBu]þ, 16), 209 (65), 151
(45), 95 (20), 75 (100), 73 (41). Anal. Calcd for
C18H28O2SSi: C, 64.23; H, 8.39; S, 9.51. Found: C,
64.35; H, 8.57; S, 9.13.
The same procedure applied to a mixture of (1R,4S,6R)-
20
12 and (1R,4S,6S)-13 furnished (1S,4S)-14, ½aŠ ¼ )95
D
(c 0.95, CHCl3), ee 94% (CHPLC, hexane/2-propanol,
99:1).
4.7. trans-Cyclohex-2-ene-1,4-diol, trans-1
To a solution of 14 (54 mg, 0.24 mmol) in THF (0.5 mL)
was added Bu4NF in THF (1 M, 0.5 mL, 0.5 mmol) and
the mixture stirred at room temperature for 20 h.
Removal of the solvent under vacuum furnished a residue
(95 mg), which purification by flash chromatography
(CHCl3/MeOH, 30:1) gave trans-16 (21 mg, 0.18 mmol,
78%).
Compound 13 (data extracted from an enriched sam-
ple): 1H NMR (250 MHz) d 7.43 (m, 2H), 7.25 (m, 3H),
5.79 (complex, 2H), 4.34 (m, 1H), 4.13 (m, 1H), 3.79 (dt,
J ¼ 11:2, 3.2 Hz, 1H), 2.47 (d, J ¼ 5:2Hz, 1H), 2.15
(ddd, J ¼ 13:4, 11.2, 4.5 Hz, 1H), 1.88 (dt, J ¼ 13:4,
3.5 Hz, 1H), 0.87 (s, 9H), 0.06 (s, 6H); 13C NMR
(62.5 MHz) d 133.9, 132.3, 129.7, 129.1, 127.1, 64.9,
64.3, 48.3, 33.9, 25.8, 18.1, )4.6, )4.7.
The same procedure applied to (1S,4S)-14 gave (1S,4S)-
0.25, CHCl3), ee 95%; lit.7
½aŠ ¼ þ144:7 (c 0.25, CHCl3), ee 94% (CHPLC,
20
1, ½aŠ ¼ )112(
c
D
20
D
hexane/2-propanol, 98:2), for (1R,4R)-1.
Acknowledgements
Occasionally, trace amounts of the (1RS,4RS,6SR)-iso-
mer of 12 and 13 were also detected (data extracted from
an enriched sample): H NMR (400 MHz) d 7.44 (m,
2H), 7.33 (m, 3H), 5.85 (ddd, J ¼ 10:0, 4.7, 1.7 Hz, 1H),
5.78 (dt, J ¼ 10:0, 0.9 Hz, 1H), 4.27 (m, 1H), 3.95 (m,
1H), 3.28 (dt, J ¼ 13:5, 3.0 Hz, 1H), 2.62 (d, J ¼ 9:4 Hz,
1H), 2.00 (m, 1H), 1.87 (ddd, J ¼ 13:5, 12.0, 10.0 Hz,
1H), 0.87 (s, 9H), 0.06 (s, 6H); 13C NMR (62.5 MHz) d
136.2, 132.1, 129.3, 127.5, 127.1, 68.4, 63.1, 49.1, 32.8,
25.8, 18.1, )4.5, )4.7.
1
We gratefully acknowledge financial support of DGES
(project BQU2001-2600) and CIRIT (project 2001SGR
001778) and a grant of Generalitat de Catalunya (to
G.M.).
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