An efficient one step dihydroxylation of 1,2-glycals with oxone in acetone

Article abstract of DOI:10.1016/S0040-4039(02)02774-0

A number of glycals have been converted into the corresponding 1,2-diols in fair to good yields. The reaction appears to proceed via the corresponding epoxide which opens in situ.

Full text of DOI:10.1016/S0040-4039(02)02774-0

TETRAHEDRON
LETTERS
Pergamon
Tetrahedron Letters 44 (2003) 907–909
An efficient one step dihydroxylation of 1,2-glycals with oxone
ꢀ
in acetone
Shikha Rani and Yashwant D. Vankar*
Department of Chemistry, Indian Institute of Technology Kanpur 208 016, India
Received 1 October 2002; revised 27 November 2002; accepted 6 December 2002
Abstract—A number of glycals have been converted into the corresponding 1,2-diols in fair to good yields. The reaction appears
to proceed via the corresponding epoxide which opens in situ. © 2003 Elsevier Science Ltd. All rights reserved.
1
0
Differentially protected sugar 1,2-diols (Scheme 1) are
useful intermediates in a variety of organic transforma-
tions. They are, for example, used in the synthesis of
our work was in progress Danishefsky et al. published
on the formation of such diols using a similar strategy.
2
chiral polyols and related natural products, in the
In connection with another project we had the opportu-
nity to study the reactions of glycals with oxone in
acetone without isolating dimethyl dioxirane and we
have now found that in one step, 1,2-diols are obtained
in fair to good yields. Five examples (Table 1) of
differently protected glycals were studied and these
gave moderate to good yields of the corresponding
diols (almost a 1:1 anomeric mixture of the diols) which
were characterised as their acetates. It was found that
the stereochemistry at C-2 is equatorial in every case. It
is noteworthy that under these conditions acid labile
acetonide protection survived (entry 4, Table 1). There
is one report in the literature where hydroxylation of
olefins using oxone in strongly acidic aqueous medium
is described. We therefore examined reactions of simple
olefins with Oxone in acetone under the present condi-
tions. Although the dihydroxylation did occur (Table
3
4
synthesis of O-glycosides, C-glycosides and in
intramolecular O-glycosylations as introduced by
5
6
7
Hindsgaul, Stork and Bols. One of the most com-
2,8
monly used methods of preparing sugar derived 1,2-
diols involves conversion of the corresponding
acetobromosugars to ortho esters followed by hydroly-
sis. However, one of the drawbacks of this method is
the necessity of using an excess of s-collidine as the
solvent in the step leading to the formation of the ortho
11
ester. Recently, OsO /NMO mediated dihydroxylation
4
3a,c
of 1,2-glycals has been reported
as an alternative to
1
2
the above method to obtain such 1,2-diols. In addition,
hydrolytic opening of 1,2-glycal epoxides could be con-
sidered an alternative for the formation of 1,2-diols
since glycal epoxides are now readily available by the
9
epoxidation of glycals using dimethyl dioxirane. While
Scheme 1.
ꢀ
Transformations in Carbohydrate Chemistry, Part 5. For Part 4, see Ref. 1.
*
Corresponding author. Fax: 0091-512-590007; e-mail: vankar@iitk.ac.in
0
040-4039/03/$ - see front matter © 2003 Elsevier Science Ltd. All rights reserved.
PII: S0040-4039(02)02774-0

9
08
S. Rani, Y. D. Vankar / Tetrahedron Letters 44 (2003) 907–909
1
), the conversion to products was generally low. The
and the corresponding epoxides are more reactive
towards ring opening.
example using cyclohexene was chosen to assess the
stereochemical outcome of the reaction. The corre-
sponding diol was acetylated and the diacetate was
found to be trans indicating clearly that the reaction
proceeds via an epoxide.
8a
Lichtenthaler et al. in their pioneering work have
shown that ulosyl bromides are useful intermediates in
carboydrate chemistry. Typically, synthesis of ulosyl
bromides involves bromination of the corresponding
enol acetates which in turn are obtained from the
corresponding ortho esters. In the present work, we
converted a 1,2-diacetate into the corresponding bro-
moacetate (Scheme 1) using red P/Br2 followed by
elimination of the elements of HBr using DBU as a
base to obtain the enol acetate. This enol acetate was
readily converted into the ulosyl bromide by bromina-
Interestingly, among the non-carbohydrate substrates,
cyclohexene gave a good yield of the diol, but stilbene
gave an epoxide (entry 10, Table 1). In other cases the
reaction was incomplete. It is clear that formation of
epoxides and their subsequent opening is better with
glycals as substrates. This is, however, not surprising
since glycals are more nucleophilic than simple olefins
Table 1. Dihydroxylation of 1,2-glycals and olefins using Oxone in acetone

S. Rani, Y. D. Vankar / Tetrahedron Letters 44 (2003) 907–909
909
tion with NBS as reported by Lichtenthaler. The
present sequence of reactions is, therefore, useful and
offers a convenient alternative to the existing method of
preparing 1,2-diols, enol acetates as well as ulosyl bro-
mides. Overall, we believe that this one step conversion
of glycals into the corresponding 1,2-diols should find
wide application in organic synthesis.
7. Bols, M. Chem. Commun. 1992, 913.
8. (a) Lichtenthaler, F. W.; Schneider-Adams, T. J. Org.
Chem. 1994, 59, 6728; (b) Broder, W.; Kunz, H. Carbo-
hydr. Res. 1993, 249, 221; (c) Schmidt, R. R.; Effen-
berger, G. Carbohydr. Res. 1987, 171, 59; (d) Wu, E.;
Wu, Q. Carbohydr. Res. 1993, 250, 327.
9. Danishefsky, S. J.; Halcomb, R. L. J. Am. Chem. Soc.
1989, 111, 6661.
Typical experimental procedure: To a solution of triben-
zyl glucal (100 mg, 0.24 mmol) in 2 mL of an acetone-
water (2:0.5) mixture, was added a mixture of Oxone
10. Iserloh, U.; Dudkin, V.; Wang, Z.-G.; Danishefsky, S. J.
Tetrahedron Lett. 2002, 43, 7027.
11. Spectral and analytical data of the two new diacetates
(
442 mg, 3 mmol) and NaHCO (121 mg, 6 mmol)
are: (corresponding to entry 3, Table 1): [h] =+34.6° (c
3
D
1
−
1
slowly at 20–25°C in small portions over a period of
0–60 min in a stoppered flask with continuous stirring.
1.1, CH Cl ). IR (neat) w : 1754 cm . H NMR
2 2 max
3
(CDCl 400 MHz): l 7.18–7.28 (m, 10H, Ar-H), 6.2 (d,
3
After the reaction was complete (TLC monitoring),
acetone was evaporated and the remaining semi-solid
mass was filtered and washed with EtOAc (3×15 mL).
The organic layer was washed with water (2×15 mL),
and brine (15 mL) and dried over Na SO . Evaporation
of solvent gave the diol which was purified by column
chromatography. Acetylation of the diol was done in
the usual manner and the product characterised by
spectroscopic and analytical means.
1H, J 3.7 Hz, H-1 a-anomer), 5.52 (d, 1H, J 8.3 Hz, H-1
b-anomer), 4.97 (t, 1H, J1,2 8.3 J2,3 9.0 Hz, H-2 b-
anomer), 4.92 (dd, 1H, J1,2 3.7 J2,3 10.0 Hz, H-2 a-
anomer), 4.59–4.81 (m, 4H, CH Ph), 3.93 (t, 1H, J
2
2,3
10.0, J3,4 9.7 Hz, H-3 a-anomer), 3.64 (t, 1H, J2,3 9, J3,4
9.3 Hz, H-3 b-anomer), 3.7–3.89 (m, 3H, H-6, H-6%, H-4),
3.36–3.39 (m, 1H, H-5), 2.04 and 1.91 (2s, 6H, 2×
-OCOCH3 a-anomer), 2.01 and 1.87 (2s, 6H, 2×
-OCOCH b-anomer), 0.8–0.84 (m, 9H, (CH ) −SiMe −),
2
4
3
3 3
2
13
−
1
0.02–0.01 (m, 6H, (CH ) Siꢀ). C NMR (100 MHz): l
69.87, 169.42, 169.09, 138.32, 138.07, 138.00, 128.46,
3
2
Acknowledgements
128.44, 128.42, 128.39, 127.94, 127.87, 127.85, 127.77,
1
7
27.70, 127.59, 92.08, 89.96, 82.57, 79.84, 77.09, 76.84,
6.50, 75.45, 75.30, 75.18, 75.01, 74.11, 72.08, 71.95,
We thank the department of Science and Technology,
New Delhi for financial support through a project
61.50, 61.44, 29.64, 25.84, 20.90, 20.83, 20.73, 20.64,
+
18.25, –5.13, –5.45. ESI: m/z 576 (M+NH
for C30
7.53%.
) . Anal. calcd
H O Si: C, 64.49; H, 7.58%. Found: C, 64.47; H,
42 8
4
(
SP/S1/G-21/2001). One of us (SR) thanks the Council
of Scientific and Industrial Research, New Delhi for a
Senior Research Fellowship. We thank the referee who
pointed out Ref. 12 to us.
(Diacetate corresponding to entry 4, Table 1): [h]
=+48°
(c 1.25, CH Cl ). IR (neat) wmax: 1757 cm . H NMR
2 2
D
−
1
1
(
CDCl 400 MHz): l 7.26–7.35 (m, 5H, Ar-H), 6.23 (d,
3
1
H, J 3.9 Hz, H-1 a-anomer), 5.64 (d, 1H, J 8.0 Hz, H-1
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26
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8
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