Catalytic asymmetric dihydroxylation of olefins with recyclable osmate-exchanged chloroapatite catalyst

Article abstract of DOI:10.1016/j.tetlet.2007.02.030

An osmate-exchanged chloroapatite (CAP-OsO₄) catalyst was prepared by an ion-exchange technique. CAP-OsO₄ efficiently catalyses asymmetric dihydroxylation of olefins including α,β-unsaturated esters and amides to afford the corresponding diols in high yields and enantioselectivities. The catalyst was reused for several cycles with consistent activity.

Full text of DOI:10.1016/j.tetlet.2007.02.030

Tetrahedron Letters 48 (2007) 2493–2496
Catalytic asymmetric dihydroxylation of olefins with
recyclable osmate-exchanged chloroapatite catalyst
Sanjay K. Dehury* and V. S. Hariharakrishnan*
SMS Pharma Research Center, C-23, Industrial Estate, Sanath Nagar, Hyderabad 500 018, India
Received 5 January 2007; revised 30 January 2007; accepted 8 February 2007
Available online 13 February 2007
Abstract—An osmate-exchanged chloroapatite (CAP-OsO4) catalyst was prepared by an ion-exchange technique. CAP-OsO4 effi-
ciently catalyses asymmetric dihydroxylation of olefins including a,b-unsaturated esters and amides to afford the corresponding
diols in high yields and enantioselectivities. The catalyst was reused for several cycles with consistent activity.
Ó 2007 Published by Elsevier Ltd.
Osmium catalyzed asymmetric dihydroxylation of
olefins, developed by Sharpless, is a very useful method
for the preparation of vicinal diols.1 In many instances,
the chiral diol units are often utilized as key structural
constituents of natural products, examples include the
synthesis of bicalutamide, diltiazem hydrochloride, and
the Taxol C-13 side chain. Nevertheless, the synthetic
utility provided by asymmetric dihydroxylation is
restricted by the high cost and toxicity due to the con-
tamination of osmium in the product. Kobayashi and
co-workers2 has developed a technique, named micro-
encapsulation, where osmium tetroxide is encapsulated
in polymer capsules. Jacobs and co-workers3 have de-
scribed immobilization of osmium tetroxide by covalent
anchoring and Yao4 has used the combination of ionic
liquids and 4-(dimethylamino)pyridine for dihydroxyl-
ation of olefins. Recently, Choudary et al. have not only
immobilized osmium tetroxide on layered double
hydroxide5 via ion-exchange but also developed the
counterionic stabilization technique6 for heterogeneiza-
tion of osmium tetroxide on nanocrystalline MgO by
for achiral dihydroxylation.
apatites are already in use in several organic
transformations.7
As a result of the above, and in conjunction with our
experience on catalytic organic transformations,8 we
believe that osmium tetroxide supported on a biocom-
patible exchanger such as chloroapatite may function
efficiently as a heterogeneous catalyst for asymmetric
dihydroxylation. In addition, the basicity provided
by chloroapatite may favor the hydrolysis of the
osmium–glycolate complex, thus enhancing the turnover
frequency of the catalyst. We herein disclose the
preparation of an osmate-exchanged chloroapatite
(CAP-OsO4) catalyst and its utility in asymmetric
dihydroxylation of olefins (Scheme 1).
In order to generalize the scope of the ion-exchange
technique for the heterogeneization of the osmate cata-
lyst through immobilization, chloroapatite and its ana-
logues including fluoroapatite and hydroxyapatite were
evaluated for dihydroxylation reactions. In the case of
chloroapatite,9 the Clꢀ ions were exchanged with
Recently, there has been research interest on weakly
amphoteric apatites as supports, mainly because of the
fact that various types of cations and anions can be
readily introduced into the framework of apatites due
to their large ion-exchange ability and such exchanged
OH
CAP-OsO4
(DHQD)2PHAL
R
R
R'
R'
t-BuOH-H2O
NMO, RT
OH
Keywords: Apatite; Asymmetric dihydroxylation; Diols; Osmium
tetroxide; a,b-Unsaturated amides.
Corresponding authors. Tel./fax: +91 40 23814709; e-mail addresses:
sanjay@smspharma.com; krishnan@smspharma.com
Yield: 71-96%
ee: 90-97%
*
Scheme 1.
0040-4039/$ - see front matter Ó 2007 Published by Elsevier Ltd.
doi:10.1016/j.tetlet.2007.02.030

2494
S. K. Dehury, V. S. Hariharakrishnan / Tetrahedron Letters 48 (2007) 2493–2496
ions to afford CAP-OsO4.10 The osmium
1–8) was added and the reaction was run for the period
of time given in the Table. Work-up afforded the corre-
sponding diols in high yields (71–96%) and enantiomeric
excess (90–97%). The recovered catalyst and ligand were
recycled five times without significant loss of activity
and selectivities as presented in Figure 1. Further, to
the filtrate, fresh aliquots of substrate and NMO were
added and the mixture was stirred for 48 h; however,
no product formation was observed. In addition, an
iodometry test confirmed the absence of leached
osmium.2b
2ꢀ
OsO4
content in the CAP-OsO4 catalyst was 0.786 mmol/g
as determined by SEM–EDX and confirmed by quanti-
tative analysis of potassium chloride formed in the
exchange process. However, the hydroxyapatite and
fluoroapatite analogues of CAP-OsO4, were obtained
with very low osmium content.
In a typical reaction,11 to a mixture of CAP-OsO4,
(DHQD)2PHAL and N-methylmorpholine-N-oxide
(NMO) in tBuOH–water (1:1), an olefin (Table 1, entries
Table 1. CAP-OsO4 catalyzed asymmetric dihydroxylation of olefins
Entry
Substrate
Product
Absol. Config.
Time (h)
12
Isolated yield (%)
93
eea (%)
OH
OH
O
O
O
O
1
2S,3R
95
OMe
OMe
OMe
OMe
OH
OH
2b
2R,3S
2S,3R
2R,3S
12
12
12
92
89
87
92
93
90
OH
O
O
OMe
3
OMe
OH
MeO
MeO
MeO
MeO
OH
O
O
4b
OMe
OMe
OH
OH
OH
OH
5
6
R
12
12
96
94
96
97
R,R
OH
HO
NH
NH
7c
S
S
24
24
73
90
92
O
O
OH
HO
NH
NH
8c
71
O
O
OH
NC
NC
CF3
CF3
a The ee was determined by HPLC analysis using Diacel Chiralcel OJ column.
b Reaction in the presence of (DHQ)2PHAL.
t
c Reaction in the presence of 2.5 mol % of OsO4, 3 mol % of (DHQD)2PHAL and 1 mol equiv of PhSO2NH2 in 1:1 BuOH–H2O.

S. K. Dehury, V. S. Hariharakrishnan / Tetrahedron Letters 48 (2007) 2493–2496
2495
References and notes
100
75
50
25
0
1. (a) Kolbe, H. C.; VanNieuwenhze, M. S.; Sharpless, K. B.
Chem. Rev. 1994, 94, 2483–2547; (b) Wai, J. S. M.; Marko,
I. E.; Svendsen, J. S.; Finn, M. G.; Jacobsen, E. N.;
Sharpless, K. B. J. Am. Chem. Soc. 1989, 111, 1123–1125;
(c) Wang, Z.-M.; Sharpless, K. B. J. Org. Chem. 1994, 59,
8302–8303; (d) Lu, X.; Xu, Z.; Yang, G. Org. Process Res.
Dev. 2000, 4, 575–576.
2. (a) Nagayama, S.; Endo, M.; Kobayashi, S. J. Org. Chem.
1998, 63, 6094–6095; (b) Kobayashi, S.; Endo, M.;
Nagayama, S. J. Am. Chem. Soc. 1999, 121, 11229–
11230; (c) Kobayashi, S.; Ishida, T.; Akiyama, R. Org.
Lett. 2001, 3, 2649–2652; (d) Ishida, T.; Akiyama, R.;
Kobayashi, S. Adv. Synth. Catal. 2003, 345, 576–579.
3. Severeyns, A.; De Vos, D. E.; Fiermans, L.; Verpoort, F.;
Grobet, P. J.; Jacobs, P. A. Angew. Chem., Int. Ed. 2001,
40, 586–589.
Yield (%)
ee (%)
1
2
3
4
5
Cycles
Figure 1. Recycling of the CAP-OsO4 catalyst for the asymmetric
dihydroxylation of methyl cinnamate.
4. Yao, Q. Org. Lett. 2002, 4, 2197–2200.
5. (a) Choudary, B. M.; Chowdari, N. S.; Jyothi, K.; Kantam,
M. L. J. Am. Chem. Soc. 2002, 124, 5341–5345; (b)
Choudary, B. M.; Chowdari, N. S.; Kantam, M. L.;
Raghavan, K. V. J. Am. Chem. Soc. 2001, 123, 9220–9221;
(c) Choudary, B. M.; Chowdari, N. S.; Madhi, S.; Kantam,
M. L. Angew. Chem., Int. Ed. 2001, 40, 4620–4623.
6. (a) Choudary, B. M.; Jyothi, K.; Kantam, M. L.;
Sreedhar, B. Adv. Synth. Catal. 2004, 346, 45–48; (b)
Choudary, B. M.; Jyothi, K.; Roy, M.; Kantam, M. L.;
Sreedhar, B. Adv. Synth. Catal. 2004, 346, 1471–1480.
7. (a) Yamaguchi, K.; Mori, K.; Mizugaki, T.; Ebitani, K.;
Kaneda, K. J. Am. Chem. Soc. 2000, 122, 7144–7145; (b)
Mori, K.; Yamaguchi, K.; Hara, T.; Mizugaki, T.;
Ebitani, K.; Kaneda, K. J. Am. Chem. Soc. 2002, 124,
11572–11573; (c) Mori, K.; Hara, T.; Mizugaki, T.;
Ebitani, K.; Kaneda, K. J. Am. Chem. Soc. 2003, 125,
11460–11461; (d) Mori, K.; Hara, T.; Mizugaki, T.;
Ebitani, K.; Kaneda, K. J. Am. Chem. Soc. 2004, 126,
10657–10666.
Moreover, various olefins (Table 1, entries 1–6) were suc-
cessfully screened in asymmetric dihydroxylation reac-
tions using CAP-OsO4. In some cases, (DHQ)2PHAL
was used as the ligand and the corresponding diols were
isolated in high yields and enantiomeric excesses (Table
1, entries 2 and 4).
In order to broaden the synthetic utility of the present
process, we studied the asymmetric dihydroxylation of
a,b-unsaturated amides. The rate of osmylation of elec-
tron deficient olefins such as a,b-unsaturated carbonyls
can be very low, while unsaturated esters still give
satisfactory reaction rates at room temperature under
standard asymmetric dihydroxylation conditions.
Unsaturated amides, although more electron rich than
the corresponding esters, react sluggishly presumably
due to the problems of osmate ester hydrolysis. How-
ever, a dramatic increase in the turnover rate could be
achieved by increasing the amount of osmate and ligand
fivefold in the presence of methane sulfonamide as an
additive.12 Thus, a,b-unsaturated amides (Table 1,
entries 7–8) were subjected to CAP-OsO4 catalyzed
asymmetric dihydroxylation. In the absence of any addi-
tive, the products were isolated in low yields. On using
methane sulfonamide, the reaction did not proceed with
much better alacrity. However, increasing the amount of
catalyst and ligand threefold and using benzene sulfon-
amide as an additive were found to be very effective
affording the desired products in good yields and high
enantiomeric excesses.
8. (a) Chaudhuri, M. K.; Dehury, S. K.; Hussain, S.
Tetrahedron Lett. 2005, 46, 6247–6251; (b) Kantam, M.
L.; Haritha, Y.; Neeraja, V.; Kavita, V. B.; Chaudhuri, M.
K.; Dehury, S. K. Adv. Synth. Catal. 2005, 347, 641–645;
(c) Chaudhuri, M. K.; Dehury, S. K.; Duarah, A.; Gogoi,
N. M.; Hussain, S.; Kantam, M. L. Adv. Synth. Catal.
2005, 347, 1349–1352.
9. Preparation of chloroapatite: Ca(NO3)2Æ4H2O (15.576 g,
0.066 mol) dissolved in water (60 mL) was brought to pH
11–12 with concentrated NH4OH and then diluted to
120 mL with water. A solution of (NH4)2HPO4 (5.28 g,
0.04 mol) and NH4Cl (0.713 g, 0.013) in 100 mL of water
was brought to pH 11–12 with concentrated NH4OH and
thereafter diluted to 160 mL with water. The calcium
solution was vigorously stirred at room temperature, and
the phosphate solution was added dropwise over a period
of 30 min to produce a milky, somewhat gelatinous
precipitate, which was then stirred and boiled for 10 min.
The precipitate was filtered, washed, dried at 80 °C
overnight, and calcined at 500 °C for 3 h. All the synthetic
steps were carried out using doubly distilled water.
10. Preparation of CAP-OsO4 catalyst: 1.5 g of chloroapatite
was suspended in 150 mL of 1.87 mmol (0.689 g) aqueous
potassium osmate solution and stirred at 25 °C for 12 h
under a nitrogen atmosphere. The solid catalyst was
filtered, washed thoroughly with 500 mL of water and
vacuum dried to obtain 1.916 g of CAP-OsO4 (0.786 mmol
of Os per g as determined by SEM–EDX).
In conclusion, CAP-OsO4 was prepared by a very simple
ion-exchange technique using chloroapatite as the sup-
port, and was found to be very efficient and reusable
for the asymmetric dihydroxylation of a variety of
olefins.
Acknowledgment
We gratefully acknowledge Mr. P. Ramesh Babu,
CMD, SMS Pharmaceuticals Ltd for unrestricted
support.
11. Procedure for asymmetric dihydroxylation of methyl cinna-
mate: CAP-OsO4 (100.2 mg, 0.08 mmol), (DHQD)2PHAL
(78.0 mg, 0.1 mmol), and N-methylmorpholine-N-oxide

2496
S. K. Dehury, V. S. Hariharakrishnan / Tetrahedron Letters 48 (2007) 2493–2496
(NMO, 15.0 mmol) were taken in a round bottomed flask
CDCl3): d (ppm) 3.32 (br s, 2H), 3.81 (s, 3H), 4.36 (d,
J = 2.8 Hz, 1H) 5.01 (d, J = 2.8 Hz, 1H), 7.36 (m, 5H);
13C NMR (50 MHz, CDCl3): d (ppm) 52.8, 74.4, 74.7,
126.2, 128.1, 128.4, 139.9, 173.1; HPLC (Daicel Chiralcel
OJ, 10% iPrOH in hexane, flow rate 1.0 mL/min):
tR = 19.1 (minor), tR = 26.7 (major). The chiral ligand
was recovered from the aqueous layer.
containing tBuOH–water (1:1, 60 mL) and stirred at room
temperature. To this mixture was added methyl cinnamate
(1.62 g, 10 mmol) slowly over 12 h. After completion of
the reaction, the CAP-OsO4 catalyst was filtered and
washed with methanol. Ethyl acetate and 1 N HCl were
added to the combined filtrates. After removing the
solvent, the crude material was chromatographed on silica
gel with EtOAc–hexanes to afford the corresponding cis-
12. Bennani, Y. L.; Sharpless, K. B. Tetrahedron Lett. 1993,
34, 2079–2082.
13. Denis, J. N.; Correa, A.; Greene, A. E. J. Org. Chem.
1990, 55, 1957–1959.
25
diol. Yield: 1.82 g (93%); ee: 95%; ½aꢁD ꢀ10.60 (c 1.0
1
CHCl3) [lit.13 ꢀ10.7 (c 1.0, CHCl3)]; H NMR (200 MHz,