Multigram synthesis of diastereomerically pure tetrahydrofuran-diols

Article abstract of DOI:10.1055/s-2007-983797

A highly efficient protocol for the large-scale oxidative cyclization of 1,5-dienes is described. This convenient ruthenium(VIII)-catalyzed (0.2 mol%) cyclization reaction allows the preparation of cis-2,5-disubstituted tetrahydrofurans in high yields (up to 92%) and excellent diastereomeric ratio (>95:5 dr). This simple and reliable method is insensitive to moisture and air and can, therefore, be carried out in an open reaction vessel. Georg Thieme Verlag Stuttgart.

Full text of DOI:10.1055/s-2007-983797

PRACTICAL SYNTHETIC PROCEDURES
2751
Multigram Synthesis of Diastereomerically Pure Tetrahydrofuran-diols
M
ultigra
m
Syn
a
thesis of
D
b
iastereomer
r
i
n
hydrofuran-
a
diols Göhler,a Stefanie Roth,a Huan Cheng,a Hülya Göksel,a Alexander Rupp,a Lars O. Haustedt,b
Christian B. W. Stark*a
a
Institut für Chemie und Biochemie, Freie Universität Berlin, Takustr. 3, 14195 Berlin, Germany
Fax +49(30)83855367; E-mail: stark@chemie.fu-berlin.de
AnalytiCon Discovery GmbH, Hermannswerder Haus 17, 14473 Potsdam, Germany
b
PSP
Received 22 December 2006
No93
Abstract: A highly efficient protocol for the large-scale oxidative cyclization of 1,5-dienes is described. This convenient ruthenium(VIII)-
catalyzed (0.2 mol%) cyclization reaction allows the preparation of cis-2,5-disubstituted tetrahydrofurans in high yields (up to 92%) and
excellent diastereomeric ratio (>95:5 dr). This simple and reliable method is insensitive to moisture and air and can, therefore, be carried
out in an open reaction vessel.
Key words: ruthenium, oxidation, cyclization, heterocycle, diastereoselectivity
R2
R4
0.2 mol% RuCl3 (stock soln),
NaIO4 on wet silica gel (2.2 equiv),
THF–CH2Cl2 (9:1), 0 °C, 1–4 h
R2
R5
R1
HO
R6
R6
R1
O
R3
R4
R3
R5
OH
up to 92% yield
>95:5 diastereomeric ratio
up to 100 mmol scale
Scheme 1 Large-scale oxidative cyclization of 1,5-dienes
As part of our interest in oxidation catalysis, we have re-
cently developed efficient protocols for the oxidative cy-
Introduction
The direct oxidative cyclization of 1,5-dienes (Scheme 2) clization of 1,5- and 1,6-dienes.5,6 We here report a
is an efficient synthetic strategy for the preparation of cis- detailed procedure for the multigram preparation of tet-
2,5-disubstituted tetrahydrofurans.1,2 In order to attain the rahydrofuran-diols, starting from representative 1,5-diene
desired cyclization reaction, powerful d0-metal–oxo re- precursors (Scheme 1). In addition, the scope and limita-
agents [Mn(VII), Ru(VIII), or Os(VIII)] are required. The tions of this particularly simple and useful synthetic meth-
same high-oxidation-state transition metals, however, are od are discussed. In order to investigate the scope of a
known to promote a multitude of other oxidation reac- large-scale oxidative cyclization procedure, dienes with
tions.3 Despite such potentially competing side reactions, mono-, di-, and trisubstituted double bonds were chosen
recent investigations have led to the development of high as substrates. Moreover, for disubstituted alkenes both
yielding procedures as well as some applications of this 1,1- and 1,2-substitution patterns as well as cis- and trans-
methodology to natural product synthesis.4 On the other configured alkenes were evaluated (Table 1). Dienes 1
hand, detailed synthetic procedures and large-scale prep- and 2 were purchased from commercial suppliers and
arations have, thus far, rarely been disclosed.
used without further purification. Cyclization precursors 3
and 5 were prepared by standard benzoate protection of
the corresponding allylic alcohols. Configurationally pure
diene 4 was synthesized from (E,E,E)-cyclododeca-1,5,9-
triene using a previously reported four-step sequence.7
For the optimized oxidative cyclization protocol inexpen-
sive ruthenium(III) chloride (0.1 M stock solution in wa-
ter) was used as a pre-catalyst (for the ruthenium
tetroxide8 generated in situ) and sodium periodate on wet
silica gel9 (2.2 equiv) was employed as the terminal oxi-
dant. A mixture of tetrahydrofuran–dichloromethane
(9:1) was identified as the optimal solvent combination.5a
Our previously reported standard procedure was generally
carried out on a 0.5 mmol scale.5a To test the impact of the
reaction scale on the yield and diastereoselectivity, a step-
wise scale-up from 0.5 mmol to 50 mmol (100-fold in-
R2
R4
R2
R5
R6
R1
HO
R6
oxidation
R1
O
R3
R4
R3
R5
OH
oxidizing agent: Mn(VII), Ru(VIII), or Os(VIII)
Scheme 2 General scheme for the oxidative cyclization of 1,5-di-
enes
SYNTHESIS 2007, No. 17, pp 2751–2754
x
x.
x
x
.
2
0
0
7
Advanced online publication: 12.07.2007
DOI: 10.1055/s-2007-983797; Art ID: E17206SS
© Georg Thieme Verlag Stuttgart · New York

2752
S. Göhler et al.
PRACTICAL SYNTHETIC PROCEDURES
Table 1 Large-Scale Oxidative Cyclization of Representative 1,5-Dienes
Entry Substrate
Product
Reaction scale Yielda
drb
(mmol)
(%)
1
2
3
1
6
50
74 (93)
>95:5
>95:5
>95:5
>95:5
>95:5
O
H
H
HO
HO
OH
OH
2
7
10
100
15
54 (74)
92 (98)
83 (83)
92 (89)
O
OBz
3
8
OBz
O
H
HO
OH
4
4c
5
9c
OR
RO
OR
O
RO
H
H
HO
OH
OBz
5
10 100
OBz
O
H
H
HO
OH
a Yield of isolated product; for comparison, yields obtained on a 0.5 mmol scale are given in parentheses.
b The diastereomeric ratio (dr) refers to the ratio of cis- and trans-tetrahydrofuran-diol. It was determined by 1H NMR and GC or HPLC analysis
of crude reaction mixtures.
c R = TBDPS.
crease) was carried out. This investigation was initially
performed using commercially available dienes 1 and 2
Scope and Limitations
(Table 1, entries 1, 2). Remarkably, despite a 100-fold in- We have recently studied the oxidative cyclization of a
crease in reaction scale, the tetrahydrofuran-diol products broad range of 1,5-dienes.5 Using the large-scale cycliza-
6 and 7 were formed in good yield and high diastereose- tion protocol described herein, representative classes of
lectivity. We next applied this procedure to the somewhat substrates delivered multigram quantities of cis-tetrahy-
more complex substrates 3–5. In addition, with these sub- drofuran-diols. At present the only class of dienes that was
strates, the applicability to other double bond substitution found to produce significant amounts of side products are
patterns and double bond configurations was evaluated. Z,Z-configured 1,5-dienes. Though these starting materi-
Pleasingly, these cyclization reactions were equally effec- als do cyclize efficiently, often high levels of overoxi-
tive (Table 1, entries 3–5). Thus, the oxidative cyclization dized ketol are formed (Scheme 3). For example, the
of dienes 3–5 yielded the expected oxygen heterocycles oxidative cyclization of Z,Z-diene 11 furnished tetrahy-
8–10 in high yields (83–92%) and excellent diastereose- drofuran-diol 12 in only 23% yield together with ketol 13
lectivity (>95:5). Notably, these reactions could be carried in 52% yield (75% total yield); thus far it has not proved
out on a 100-mmol scale providing up to 27.5 g of diaste- possible to suppress the formation of such byproducts. On
reomerically pure cyclization product (Table 1, entries 3, the other hand, cis-erythro-substituted ketol 13 could eas-
5). In view of the range of application and reliability of ily be converted into the corresponding tetrahydrofuran-
this large-scale procedure, it is also worth mentioning that
moisture and air do not pose any problems. Therefore,
these reactions can be carried out in an open vessel with
R
R
O
H
H
the same reaction outcome. Even additional water (up to
1.0 vol%) does not have any deleterious effects, which
nicely exemplifies the robust nature of this synthetic pro-
cedure.
HO
OH
R
R
(i)
12
+
75% yield
(12/13 = 1:2.2)
11 (R = n-Pr)
(ii)
R
R
O
Finally, it is worth noting that enzymatic desym-
metrizations10 of Cs-symmetric tetrahydrofuran-diols 6, 7,
and 9 have been reported.11 Therefore, optically pure
products (with up to four chiral centers) are available in a
two-step sequence consisting of diastereoselective oxida-
tive cyclization followed by lipase-catalyzed enantiose-
lective esterification.
H
H
O
OH
13
Scheme 3 Ketols as side products in the oxidative cyclization of
Z,Z-configured 1,5-dienes and their diastereoselective reduction.
Reagents and conditions: (i) aq 0.1 M RuCl3 (0.2 mol%), NaIO4 (2.2
equiv) on wet silica gel, THF–CH2Cl2 (9:1), 0 °C, 75% (ratio 12/13
1:2.2); (ii) L-Selectride (1.1 equiv), THF, –78 °C, 95% (85:15 dr).
Synthesis 2007, No. 17, 2751–2754 © Thieme Stuttgart · New York

PRACTICAL SYNTHETIC PROCEDURES
Diastereomerically Pure Tetrahydrofuran-diols
2753
diol 12. The diastereoselective carbonyl reduction12,13 us-
ing L-Selectride delivered alcohol 12 in high yield (95%)
and with good diastereomeric ratio (85:15 dr; unopti-
mized) furnishing predominantly the same meso-isomer
as obtained from the oxidative cyclization (Scheme 3).
duced pressure. Column chromatography (EtOAc–hexane) yielded
the analytically pure product.
2-Hydroxy-2-[5-(1-hydroxy-1-methylethyl)-2-methyltetrahy-
drofuran-2-yl]ethyl Benzoate (8)
Mp 66–68 °C; Rf = 0.41 (hexane–EtOAc, 1:4).
In summary, we have presented a procedure for the multi-
gram oxidative cyclization of representative 1,5-dienes.
Different classes of diene substrates provided the desired
cyclization products in high yields and excellent diastere-
oselectivity. Thus, di-, tri-, and tetra-2,5-substituted tet-
rahydrofurans were produced employing identical
oxidation conditions. Moreover, starting from simple
achiral 1,5-dienes up to four stereogenic centers were cre-
ated in this single step transformation. The potential of our
oxidative cyclization protocol to be scaled up is nicely
demonstrated for substrates 3 and 5 by the 200-fold scal-
ing up (0.5 mmol to 100 mmol) of the reaction. Remark-
ably, without any changes to the reaction conditions
almost identical yields and diastereoselectivities were ob-
tained irrespective of the reaction scale. These findings
clearly underpin the usefulness and synthetic applicability
of this unique cyclization reaction.
FT-IR (KBr): 3323, 2971, 2935, 1709, 1453, 1287, 1128, 1179,
1082, 1036, 708 cm–1.
1H NMR (500 MHz, CDCl3): d = 1.08 (s, 3 H, C2-CH3), 1.23 [s, 6
H, C5-COH(CH3)2], 1.65 (ddd, 3J = 7.4, 8.4 Hz, 2J = 12.4 Hz, 1 H,
C3-Ha), 1.88 (m, 1 H, C4-Ha), 1.93 (m, 1 H, C4-Hb), 2.20 (ddd,
3J = 5.4, 9.2 Hz, 2J = 12.4 Hz, 1 H, C3-Hb), 3.33 (s, 1 H, OH), 3.80
3
[dd, 3J = 3.3, 8.0 Hz, 1 H, C2-C(OH)H-R], 3.84 (t, J = 7.3 Hz, 1
H, C5-H), 4.34 (dd, 3J = 8.0 Hz, 2J = 11.6 Hz, 1 H, C2-
CH(OH)CH2OBz], 4.50 [dd, 3J = 3.3, 2J = 11.6 Hz, 1 H, C2-
4
3
CH(OH)CH2OBz], 7.39 (ddd, J = 1.4 Hz, J = 7.8, 8.3 Hz, 2 H,
Ar), 7.51 (tt, 4J = 1.4 Hz, 3J = 7.8 Hz, 1 H, Ar), 8.02 (ddd, 4J = 1.4,
1.4 Hz, 3J = 8.4 Hz, 2 H, Ar).
13C NMR (125 MHz, CDCl3): d = 23.1 (C4), 25.3 (C2-CH3), 26.6
[C5-C(OH)(CH3)2], 27.7 [C5-C(OH)(CH3)2], 35.6 (C3), 66.6 [C2-
CH(OH)CH2OBz], 71.9 [C5-COH(CH3)2], 75.4 (C2), 84.3 (C2-
CHOH), 85.7 (C5), 128.4 (Ar), 129.8 (Ar), 130.1 (Ar), 133.1 (Ar),
167.0 (C=O).
MS (FAB+): m/z (%) = 59 (18, [C3H7O]+), 77 (45, [Ph]+), 105 (100,
[PhCO]+), 125 (27, [C8H15O2 –H2O]+), 143 (86, [C8H15O2]+), 275
(6, [M – H2O – CH3]+), 291 (0.2, [M – H2O]+), 293 (0.05, [M –
CH3]+), 309 (0.02, [M + H]+).
All reagents were used as purchased from commercial suppliers.
Column chromatography: Merck silica gel 60, 0.040–0.063 mm
(230–400 mesh). TLC: pre-coated aluminum sheets, Merck silica
gel 60, F254; detection by UV and by cerium/molybdenum soln
[phosphomolybdic acid (25 g), Ce(SO4)2·H2O (10 g), concd H2SO4
(60 mL), H2O (940 mL)]. 1H and 13C NMR spectra were recorded at
r.t. in CDCl3 on a Bruker AC 500 spectrometer with TMS as internal
standard or relative to the resonance of the solvent (1H NMR:
CDCl3, d = 7.24; 13C NMR: CDCl3, d = 77.0). Two dimensional
NMR techniques (COSY, HMBC, HMQC) were used where appro-
HRMS: m/z [M – CH3]+ calcd for C16H21O5: 293.139; found:
293.139.
4-(tert-Butyldiphenylsiloxy)-1-{5-[4-(tert-butyldiphenylsiloxy)-
1-hydroxybutyl]tetrahydrofuran-2-yl}butan-1-ol (9)
Rf = 0.23 (hexane–EtOAc, 2:1).
FT-IR (KBr): 3413, 3070, 2953, 2583, 1739, 1472, 1389, 1240,
1112, 823, 701, 506 cm–1.
1
priate, to aid in the assignment of signals in the H and 13C NMR
1H NMR (500 MHz, CDCl3): d = 1.03 (s, 9 H, t-Bu), 1.55 (m, 1 H,
H3¢), 1.63 (m, 2 H, H3, H2¢), 1.78 (m, 2 H, H6¢, H2), 1.91 (m, 1 H,
H6), 2.69 (br s, 1 H, OH), 3.44 (m, 1 H, H4), 3.69 (dt, 4J = 1.4 Hz,
3J = 5.9 Hz, 2 H, H1/H1¢), 3.82 (m, 1 H, H5), 7.37 (m, 6 H, Ar), 7.64
(m, 4 H, Ar).
13C NMR (125 MHz, CDCl3): d = 19.2 [C(CH3)3], 26.9 [C(CH3)3],
28.1 (C6), 28.8 (C2), 30.8 (C3), 63.9 (C5), 74.0 (C4), 82.6 (C1),
127.6 (Ar), 129.6 (Ar), 133.9 (Ar), 135.6 (Ar).
spectra. MS were recorded on a Varian MAT 771, MAT 112 S. FT-
IR spectra were obtained on a Nicolet 5 SXC with DTGS detector.
Elemental analyses were measured on a Perkin-Elmer 2400 CHN
elemental analyzer. Melting points were measured on a Büchi 510
melting point apparatus, and are uncorrected. Compounds 61b and
7
14 have been prepared previously. Analytical data for these tetrahy-
drofuran-diols are consistent with those previously reported.
MS (EI, 180 °C): m/z (%) = 72 (24, [THF – 2 H]+), 77 (10, [Ph]+),
199 (100, [HSiPh2]+), 134 (32, [C6H12O3 + 2 H]+), 433 (1,
[C24H34O5Si]+), 649 (1, [M – C4H9 – H2O]+), 667 (1, [M – C4H9]+).
Sodium Periodate on Wet Silica Gel (480 mmol Scale)
NaIO4 (103.0 g, 481.3 mmol) was suspended in H2O (240 mL) and
the mixture was heated to 70 °C with magnetic stirring in a 2 L
flask. Silica gel (400 g, 230–400 mesh) was added to this slightly
cloudy soln in one portion (at 70 °C). After addition of silica gel, the
flask was removed from the heating bath, stoppered, and vigorously
shaken until a fine, homogeneous powder had formed. The final
concentration of solid-supported periodate was 0.64 mmol/g.
HRMS: m/z [M – C4H9]+ calcd for C40H51O5Si2: 667.328; found:
667.327.
Anal. Calcd for C44H60O5Si2: C, 72.88; H, 8.34. Found C, 72.35; H,
8.28.
Ruthenium Tetroxide Catalyzed Oxidative Cyclization of 1,5-
Dienes (100 mmol Scale); General Procedure
2-Hydroxy-2[5-(1-hydroxypropyl)tetrahydrofuran-2-yl]ethyl
Benzoate (10)
The 1,5-diene (100 mmol, 1 equiv) was added to a suspension of
NaIO4 on wet silica gel (336.6 g, 220 mmol, 2.2 equiv) in THF
(1800 mL) and CH2Cl2 (200 mL). The mixture was cooled to 0 °C.
A 0.1 M stock soln of RuCl3 in H2O (2.0 mL, 0.2 mmol, 0.002
equiv) was added dropwise to this suspension and the mixture was
stirred mechanically at 0 °C. The reaction progress was monitored
by TLC. After complete conversion of the starting material the re-
action was quenched by addition of i-PrOH (20 mL, excess). The
mixture was stirred for another 10 min and filtered followed by
careful washing with EtOAc. The solvent was removed under re-
Mp 92–94 °C; Rf = 0.12 (hexane–EtOAc, 2:1).
FT-IR (KBr): 3323, 2961, 2927, 2883, 1714, 1452, 1277, 1124, 906,
719 cm–1.
3
1H NMR (500 MHz, CDCl3): d = 0.96 [t, J = 6.7 Hz, 3 H, C5-
CH(OH)CH2CH3], 1.40 [dq, 3J = 6.7, 6.7 Hz,
2 H, C5-
CH(OH)CH2CH3], 1.80 (m, 1 H, C3-Ha), 2.02 (m, 3 H, C3-Hb, C4-
H2), 3.80 [m, 1 H, C5-CH(OH)CH2CH3], 3.86 (m, 1 H, C5-H), 3.97
(td, 3J = 2.9, 4.8 Hz, 1 H, C2-H), 4.11 [m, 1 H, C2-
3
2
CH(OH)CH2OBz], 4.39 [dd, J = 5.0 Hz, J = 11.4 Hz, 1 H, C2-
Synthesis 2007, No. 17, 2751–2754 © Thieme Stuttgart · New York

2754
S. Göhler et al.
PRACTICAL SYNTHETIC PROCEDURES
3
2
CH(OH)CH2OBz], 4.43 [dd, J = 7.0 Hz, J = 11.4 Hz, 1 H, C2-
Angew. Chem. 2001, 113, 4628. With OsO4: (i) de
Champdoré, M.; Lasalvia, M.; Piccialli, V. Tetrahedron
Lett. 1998, 39, 9781. (j) Donohoe, T. J.; Butterworth, S.
Angew. Chem. Int. Ed. 2003, 42, 948; Angew. Chem. 2003,
115, 978.
4
3
CH(OH)CH2OBz], 7.41 (ddd, J = 1.4 Hz, J = 8.3, 7.0 Hz, 2 H,
Ar), 7.54 (tt, 4J = 1.4 Hz, 3J = 7.0 Hz, 1 H, Ar), 8.03 (ddd, 4J = 1.4,
1.4 Hz, 3J = 8.3 Hz, 2 H, Ar).
13C NMR (125 MHz, CDCl3): d = 10.4 [C5-CH(OH)CH2CH3],
24.2 (C3), 26.3 (C4), 28.6 [C5-CH(OH)CH2CH3], 67.0 [C2-
CH(OH)CH2OBz], 72.3 [C2-CH(OH)CH2OBz], 74.2 [C5-
CH(OH)CH2CH3], 78.9 (C2), 88.9 (C5), 128.4 (Ar), 129.8 (Ar),
130.0 (Ar), 133.1 (Ar), 166.8 (C=O).
(2) For a review on the mechanistically related oxidative
cyclization of bishomoallylic alcohols, see: Hartung, J.;
Greb, M. J. Organomet. Chem. 2002, 661, 67.
(3) Oxidation in Organic Chemistry, ACS Monograph Series
No. 186; Hudlicky, M., Ed.; American Chemical Society:
Washington DC, 1990.
(4) (a) Kocieński, P. J.; Brown, R. C. D.; Pommier, A.; Procter,
M.; Schmidt, B. J. Chem. Soc., Perkin Trans. 1 1998, 9.
(b) Cecil, A. R. L.; Brown, R. C. D. Org. Lett. 2002, 4, 3715.
(c) Lygo, B.; Slack, D.; Wilson, C. Tetrahedron Lett. 2005,
46, 6629. (d) Göksel, H.; Stark, C. B. W. Org. Lett. 2006, 8,
3433.
(5) (a) Roth, S.; Göhler, S.; Cheng, H.; Stark, C. B. W. Eur. J.
Org. Chem. 2005, 4109. (b) Göhler, S.; Stark, C. B. W. Org.
Biomol. Chem. 2007, 5, 1605.
MS (pos. FAB): m/z (%) = 57 (81, [C3H5O]+), 59 (37, [C3H7O]+), 77
(70, [Ph]+), 105 (100, [PhCO]+), 277 (5, [MH – H2O]+), 295 (6, [M
+ H]+), 317 (8, [M + Na]+).
HRMS: m/z [M – OH]+ calcd for C16H21O4: 277.144; found:
277.144.
Anal. Calcd for C16H22O5: C, 65.29; H, 7.53. Found C, 65.15; H,
7.41.
Acknowledgment
(6) Roth, S.; Stark, C. B. W. Angew. Chem. Int. Ed. 2006, 45,
This research was generously supported by the Deutsche For-
schungsgemeinschaft (Grant-No.: STA 634/1-1), and by PhD fel-
lowships to S.G. from the Fonds der Chemischen Industrie and to
S.R. from the Ernst-Schering-Stiftung. We are grateful to Prof.
H.-U. Reissig (Freie Universität Berlin, Germany) for helpful dis-
cussions and ongoing support.
6218; Angew. Chem. 2006, 118, 6364.
(7) For details see ref. 4d; cf. also: Neogi, P.; Doundoulakis, T.;
Yazbak, A.; Sinha, S. C.; Sinha, S. C.; Keinan, E. J. Am.
Chem. Soc. 1998, 120, 11279.
(8) For a recent review on RuO4-catalyzed oxidations, see:
Plietker, B. Synthesis 2005, 2453.
(9) Zhong, Y.-L.; Shing, T. K. M. J. Org. Chem. 1997, 62, 2622;
see also ref. 5 and 6.
References
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Chem. 1981, 46, 3936. (b) Albarella, L.; Musumeci, D.;
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46, 1623. With KMnO4: (e) Klein, E.; Rojahn, W.
Tetrahedron 1965, 21, 2353. (f) Walba, D. M.; Wand, M.
D.; Wilkes, M. C. J. Am. Chem. Soc. 1979, 101, 4396.
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(b) Nakazaki, M.; Naemura, K.; Makimura, M.; Matsuda,
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Synthesis 2007, No. 17, 2751–2754 © Thieme Stuttgart · New York