Highly facile biomimetic regioselective ring opening of epoxides to halohydrins in the presence of β-cyclodextrin

Article abstract of DOI:10.1016/S0040-4020(02)00614-2

Highly regioselective ring opening of epoxides to halohydrins has been carried out in impressive yields with hydrogen and lithium halides in presence of β-cyclodextrin using water as solvent.

Full text of DOI:10.1016/S0040-4020(02)00614-2

TETRAHEDRON
Pergamon
Tetrahedron 58 92002) 6003±6008
Highly facile biomimetic regioselective ring opening of epoxides
to halohydrins in the presence of b-cyclodextrinq
M. Arjun Reddy, K. Surendra, N. Bhanumathi and K. Rama Raop
Organic Chemistry Division I, Indian Institute of Chemical Technology, Hyderabad 500 007, India
Received 4 January 2002; revised 20 May 2002; accepted 13 June 2002
AbstractÐHighly regioselective ring opening of epoxides to halohydrins has been carried out in impressive yields with hydrogen and
lithium halides in presence of b-cyclodextrin using water as solvent. q 2002 Elsevier Science Ltd. All rights reserved.
1. Introduction
tial appeared to be from the easily accessible epoxides and
inexpensive hydrogen halides if the disadvantages asso-
ciated with this method such as unwanted byproduct forma-
tion and low regioselectivities can be overcome. The best
choice appeared to be through supramolecular catalysis
involving cyclodextrins and using water as solvent. Such
reactions do not generate any toxic waste products either
9Scheme 1).
There is continued interest in the regioselective ring
opening of oxiranes to vicinal halohydrins due to their
signi®cance1 especially in the synthesis of halogenated
marine natural products2 and in various organic synthetic
transformations.3 But the most general method of preparing
these vic-halohydrins by the ring opening of epoxides with
hydrogen halides suffers from various disadvantages such
as pharmacologically inactive halohydrins, unwanted
byproducts and low regioselectivity.4 This has spurred
research in different directions ranging from elemental
halogens,5 metal halides such as LiX,6 TiCl4±LiX,7 CeCl3
7H2O±NaI,8 to chlorosilanes,9 haloboranes10 etc. However,
these reagents also suffer from various disadvantages such
as in situ preparation of reagents, longer reaction times
9up to several days in some cases), re¯ux temperatures,
hygroscopic nature of catalysts etc. In view of these limi-
tations, there is still the need for a widely applicable and
alternate approach, preferably using water as solvent which
is gaining increasing importance in the present day organic
synthesis. Amongst various approaches, the most attractive
methodology with wide applicability and industrial poten-
Cyclodextrins are cyclic oligosaccharides possessing hydro-
phobic cavities which bind substrates selectively and cata-
lyze chemical reactions with high selectivity. They catalyze
reactions by supramolecular catalysis involving reversible
formation of host±guest complexes by non-covalent
bonding as seen in enzymes. Complexation depends on
the size, shape and hydrophobicity of the guest molecule.
Thus mimicking of biochemical selectivity that shows shape
and substrate selectivity will be superior to chemical selec-
tivity. Our earlier expertise in the ®eld of biomimetic
modeling of organic chemical reactions11 prompted us to
attempt the regioselective ring opening of epoxides with
hydrogen halides in the presence of b-cyclodextrin
9b-CD) as this is one of the most useful synthetic transfor-
mations with a variety of applications.
2. Results and discussion
The reaction was carried out by the in situ formation of the
b-CD complex of the epoxide 91) in water followed by the
addition of hydrogen halide or lithium halide and stirring at
room temperature to give the corresponding halohydrins 92)
in impressive yields 9Tables 1and 2). The reaction goes
smoothly at room temperature without the formation of
any side products or rearrangements. The catalyst can be
easily recovered and reused. b-CD has been chosen as the
catalyst since it is inexpensive and easily accessible.
However, these reactions do take place with a-CD. Though
inclusion complexation takes place in situ during the
Scheme 1.
q IICT Communication No. 02.01.03.
Keywords: epoxides; hydrogen halides and lithium halides; cyclodextrin;
supramolecular catalysis; water.
p
Corresponding author. Tel.: 191-40-7160123/24; fax: 191-40-7160757;
e-mail: ramaraok@iict.ap.nic.in
0040±4020/02/$ - see front matter q 2002 Elsevier Science Ltd. All rights reserved.
PII: S0040-4020902)00614-2

6004
M. A. Reddy et al. / Tetrahedron 58 &2002) 6003±6008
Table 1. Biomimetic synthesis of halohydrins from oxiranes and hydrogen halides
Entry
Epoxide 91)
Reagent
Producta 92)
Yieldb 9%)
1HCl
2
3
2a. XˆCl
96
90
89
HBr
HI
2b. XˆBr
2c. XˆI
4
5
6
HCl
HBr
HI
2d. XˆCl
2e. XˆBr
2f. XˆI
94
88
90
7
8
9
HCl
HBr
HI
2g. XˆCl
2h. XˆBr
2i. XˆI
92
94
89
10
11
1
HCl
HBr
2
2j. XˆCl
2k. XˆBr
2l. XˆI
98
92
90
HI
13
14
1
HCl
HBr
5
2m. XˆCl
2n. XˆBr
2o. XˆI
93
90
95
HI
16
17
1
HCl
HBr
8
2p. XˆCl
2q. XˆBr
2r. XˆI
90
88
87
HI
19
20
21HI
HCl
HBr
2s. XˆCl
2t. XˆBr
2u. XˆI
88
90
84
22
23
24
HCl
HBr
HI
2v. XˆCl
2w. XˆBr
2x. XˆI
92
90
87
25
26
27
HCl
HBr
HI
2y. XˆCl
2z. XˆBr
2z0. XˆI
89
91
95
a
All products were characterized by 1H NMR, Mass and IR spectra data.
Isolated yields.
b

M. A. Reddy et al. / Tetrahedron 58 &2002) 6003±6008
Table 2. Biomimetic synthesis of halohydrins from oxiranes and lithium halides
6005
Entry
Epoxide 91)
Reagent
Producta 92)
Yieldb 9%)
1LiCl
2
3
2a. XˆCl
89
85
82
LiBr
LiI
2b. XˆBr
2c. XˆI
4
5
6
LiCl
LiBr
LiI
2d. XˆCl
2e. XˆBr
2f. XˆI
90
81
85
7
8
9
LiCl
LiBr
LiI
2g. XˆCl
2h. XˆBr
2i. XˆI
85
90
87
10
11
12
LiCl
LiBr
LiI
2j. XˆCl
2k. XˆBr
2l. XˆI
94
89
86
13
14
15
LiCl
LiBr
LiI
2m. XˆCl
2n. XˆBr
2o. XˆI
89
82
84
16
17
18
LiCl
LiBr
LiI
2p. XˆCl
2q. XˆBr
2r. XˆI
87
81
85
19
20
21LiI
LiCl
LiBr
2s. XˆCl
2t. XˆBr
2u. XˆI
78
84
75
22
23
24
LiCl
LiBr
LiI
2v. XˆCl
2w. XˆBr
2x. XˆI
85
82
79
25
26
27
LiCl
LiBr
LiI
2y. XˆCl
2z. XˆBr
2z0. XˆI
83
80
77
a
All products were characterized by 1H NMR, Mass and IR spectra data.
Isolated yields.
b

6006
M. A. Reddy et al. / Tetrahedron 58 &2002) 6003±6008
reaction, the complexes have been isolated and charac-
anhydrous sodium sulfate and the solvent was removed in
vacuum. The crude product was puri®ed by silica gel
column chromatography using ethyl acetate: hexane 92:8)
as eluent. All the products were characterized by 1H NMR,
IR, and Mass spectral data and compared with the data
reported in the literature for the authentic samples.
1
terized by powder X-ray12 and H NMR studies.13 Here,
the role of CD appears to be not only to activate the
epoxides but also to promote highly regioselective ring
opening due to inclusion complex formation. Thus, in this
new biomimetic methodology, chloro, bromo and iodo-
hydrins can be obtained in high yields. Since these reactions
are taking place in the microenvironment of cyclodextrin,
high selectivities are obtained without any side product
formation. Especially notable is the selectivity obtained
with styrene epoxides 9entries 13±18) where the halide
ion attacked the terminal carbon whereas in the procedures
reported so far, either the halide ion attacked the benzylic
carbon or mixtures were obtained. In this methodology even
the acid sensitive ether linkages in 2a±2i are left intact due
to microenvironmental effect in spite of the epoxides being
opened with hydrogen halides. Though these reactions can
also be carried out using lithium halides, the yields obtained
were comparatively lower. However, other metal halides
such as NaX, KX did not work out.
4.2.1. 1-Chloro-3-phenoxy-2-propanol *2a).8 1H NMR
9CDCl3, 200 MHz) d 2.50 9d, 1H, Jˆ3.2 Hz), 3.70±3.85
9m, 2H), 4.10±4.15 9m, 2H), 4.18±4.25 9m, 1H), 6.90±7.0
9m, 3H), 7.30±7.40 9m, 2H); MS 9EI) m/z: 186 9M1); IR
9KBr) 3450 cm21
.
4
1
4.2.2. 1-Bromo-3-phenoxy-2-propanol *2b).1 H NMR
9CDCl3, 200 MHz) d 2.45 9d, 1H, Jˆ3.0 Hz), 3.75±3.80
9m, 2H), 4.05±4.10 9m, 2H), 4.15±4.20 9m, 1H), 6.90±
7.05 9m, 3H), 7.30±7.35 9m, 2H); MS 9EI) m/z: 230 9M1);
IR 9KBr) 3500 cm21
.
4
1
4.2.3. 1-Iodo-3-phenoxy-2-propanol *2c).1 H NMR
9CDCl3, 200 MHz) d 2.40 9brs, 1H), 3.30±3.55 9m, 2H),
3.80±4.10 9m, 3H), 6.75±7.0 9m, 3H), 7.15±7.35 9m, 2H);
MS 9EI) m/z: 278 9M1); IR 9KBr) 3500 cm21
.
3. Conclusion
4.2.4. 1-Chloro-3-*4-chlorophenoxy)-2-propanol *2d).17
1H NMR 9CDCl3, 200 MHz) d 2.40 9d, 1H, Jˆ3.2 Hz),
3.70±3.80 9m, 2H), 4.05±4.15 9m, 2H), 4.19±4.25 9m,
1H), 6.85 9d, 2H, Jˆ9.2 Hz), 7.25 9d, 2H, Jˆ9.2 Hz); MS
Thus, it has been shown for the ®rst time that halohydrins
with high synthetic potential can be made in a biomimetic
fashion with high regioselectivity from the easily accessible
epoxides and inexpensive hydrogen halides in the presence
of b-CD. Thus, this high selectivity, which was not possible
with earlier methods could be achieved due to the inclu-
sion complex formation of epoxides with b-cyclodextrin
which then reacted with hydrogen halides. Further potential
applications of this reaction are under study.
9EI) m/z: 220 9M1); IR 9KBr) 3510 cm21
.
4.2.5. 1-Bromo-3-*4-chlorophenoxy)-2-propanol *2e).17
1H NMR 9CDCl3, 200 MHz) d 2.05 9d, 1H, Jˆ3.2 Hz),
3.45±3.60 9m, 2H), 3.95±4.05 9m, 2H), 4.10±4.20 9m,
1H), 6.75 9d, 2H, Jˆ8.2 Hz), 7.20 9d, 2H, Jˆ8.2 Hz); MS
9EI) m/z: 264 9M1); IR 9KBr) 3515 cm21
.
4. Experimental
4.1. General
7
1
4.2.6. 1-Iodo-3-*4-chlorophenoxy)-2-propanol *2f).1
H
NMR 9CDCl3, 200 MHz) d 2.40 9brs, 1H), 3.35±3.40 9m,
1H), 3.45±3.50 9m, 1H), 3.95±4.0 9m, 1H), 4.05±4.10 9m,
All reagents were purchased from Fluka or SD Fine
Chemicals and were used with out further puri®cation.
Silica gel 9100±200 mesh) for chromatography was
purchased from SD Fine Chemicals and compounds were
visualized on analytical thin layer chromatograms 9TLC) by
UV light 9254 nm). Optical rotations were measured in
2H), 6.85 9d, 2H, Jˆ8.2 Hz), 7.25 9d, 2H, Jˆ8.2 Hz); MS
1
9EI) m/z: 31 2 9M ); IR 9KBr) 3540 cm21
.
4.2.7. 1-Chloro-3-*4-acetylphenoxy)-2-propanol *2g).
Pale yellow liquid, H NMR 9CDCl3, 200 MHz) d 2.55 9s,
1
3H), 3.0 9brs, 1H), 3.75±3.80 9m, 2H), 4.0±4.40 9m, 3H),
6.90 9d, 2H, Jˆ7.6 Hz), 7.95 9d, 2H, Jˆ7.6 Hz). 13C NMR
9CDCl3, 50 MHz) d 26.21, 45.69, 68.78, 69.61, 114.25,
130.65, 162.31, 197.47; MS 9EI) m/z 228 9M1). Anal.
calcd for C11H13ClO3: C, 57.78; H, 5.73. Found: C, 57.80;
H, 5.68.
1
chloroform. H NMR spectra were recorded at 200, 300 or
400 MHz. Chemical shifts are given in ppm relative to
tetramethylsilane 9TMS), which is used as internal standard
and coupling constants 9J) are reported in Hz. IR absorp-
tions 9in cm21) and the molecular ions and/or base peaks in
MS are given.
4.2.8. 1-Bromo-3-*4-acetylphenoxy)-2-propanol *2h).
White Solid, mp 64±668C; H NMR 9CDCl3, 200 MHz) d
1
4.2. General procedure for the preparation of
halohydrins from the corresponding epoxides
2.55 9s, 3H), 3.45±3.65 9m, 2H), 4.10±4.20 9m, 3H), 6.90 9d,
2H, Jˆ7.6 Hz), 7.90 9d, 2H, Jˆ7.6 Hz), 13C NMR 9CDCl3,
50 MHz) d 26.11, 34.53, 69.05, 69.33, 114.09, 130.46,
162.08, 197.12; MS 9EI) m/z 273 9M1). Anal. calcd for
C11H13BrO3: C, 48.37, H, 4.80. Found: C, 48.45; H, 4.75.
b-Cyclodextrin 91mmol) was dissolved in water 925 mL) at
608C, epoxide 91mmol) dissolved in methanol/acetone
91mL) was added slowly with stirring and cooled to room
temperature. Then 1.5 mmol of hydrogenhalide or lithium
halide was added and stirring at room temperature was
continued 912 h in case of hydrogenhalide or 24 h for
lithium halide). It was extracted with ethyl acetate
93£25 mL) and ®ltered. The organic layer was dried over
4.2.9.
1-Iodo-3-*4-acetylphenoxy)-2-propanol
*2i).
1
Yellow solid, mp 68±708C; H NMR 9CDCl3, 200 MHz)
d 2.55 9s, 3H), 3.30±3.50 9m, 2H), 3.90±4.10 9m, 3H),
6.90 9d, 2H, Jˆ7.8 Hz), 7.90 9d, 2H, Jˆ7.8 Hz), 13C NMR

M. A. Reddy et al. / Tetrahedron 58 &2002) 6003±6008
6007
9CDCl3, 50 MHz) d 8.84, 26.21, 69.12, 70.57, 114.66,
130.64, 162.75, 196.96; MS 9EI) m/z 320 9M1). Anal.
calcd for C11H13IO3: C, 41.27; H, 4.09. Found: C, 41.34;
H, 4.10.
4.80±4.88 9m, 1H), 7.20±7.40 9m, 4H); MS 9EI) m/z: 282
9M1); IR 9KBr) 3460, 2960 cm21
.
4.2.19. 2-Chloro cyclohexanol *2s).8 1H NMR 9CDCl3,
200 MHz) d 1.20±1.40 9m, 3H), 1.60±1.85 9m, 3H),
2.10±2.20 9m, 1H), 2.30±2.40 9m, 1H), 3.50±3.60 9m,
1H), 3.90±4.00 9m, 1H); MS 9EI) m/z: 134 9M1); IR
4.2.10. 1-Chloro-3-*4-methoxyphenyl)-2-propanol *2j).
Pale yellow liquid, H NMR 9CDCl3, 200 MHz) d 2.80 9d,
1
9KBr) 3430, 2960 cm21
.
2H, Jˆ7.8 Hz), 3.50 9dd, 1H, Jˆ5.2, 9.6 Hz), 3.60 9dd, 1H,
Jˆ4.4, 9.6 Hz), 3.80 9s, 3H), 3.90±4.0 9m, 1H), 6.80 9d, 2H,
Jˆ8.0 Hz), 7.12 9d, 2H, Jˆ8.0 Hz); 13C NMR 9CDCl3,
50 MHz) d 40.20, 47.80, 55.10, 72.10, 116.50, 130.10,
131.22, 158.32; MS 9EI) m/z: 200 9M1); IR 9KBr)
3485 cm21. Anal. calcd for C10H13ClO2: C, 59.86; H, 6.53.
Found: C, 59.72; H, 6.44.
4
1
4.2.20. 2-Bromo cyclohexanol *2t).1 H NMR 9CDCl3,
200 MHz) d 1.20±1.45 9m, 3H), 1.60±1.80 9m, 3H),
2.10±2.25 9m, 1H), 2.30±2.40 9m, 1H), 3.55±3.65 9m,
1H), 3.80±3.95 9m, 1H); MS 9EI) m/z: 178 9M1); IR
9KBr) 3432, 2965 cm21
.
4.2.21. 2-Iodo cyclohexanol *2u).1 H NMR 9CDCl3,
200 MHz) d 1.20±1.60 9m, 4H), 1.80±1.90 9m, 1H), 2.0±
2.20 9m, 2H), 2.40±2.50 9m, 1H), 3.50±3.65 9m, 1H), 3.95±
4.05 9m, 1H); MS 9EI) m/z: 226 9M1); IR 9KBr) 3425,
4
1
4.2.11. 1-Bromo-3-*4-methoxyphenyl)-2-propanol *2k).
Pale yellow liquid, H NMR 9CDCl3, 200 MHz) d 2.05
1
9brs, 1H), 2.85 9d, 2H, Jˆ6.2 Hz), 3.35 9dd, 1H, Jˆ4.8,
9.6 Hz), 3.55 9dd, 1H, Jˆ3.8, 9.6 Hz), 3.80 9s, 3H), 3.95±
4.0 9m, 1H). 6.85 9d, 2H, Jˆ8.6 Hz), 7.15 9d, 2H,
2960 cm21
.
Jˆ8.6 Hz); 13C NMR 9CDCl3, 50 MHz)
d
39.10,
4.2.22. 1,3-Dichloro-2-propanol *2v).8 1H NMR 9CDCl3,
200 MHz) d 2.50 9brs, 1H), 3.60±3.80 9m, 4H), 4.0±4.10
9m, 1H); MS 9EI) m/z 128 9M1).
41.42, 55.10, 70.05, 116.22, 130.10, 131.05, 158.10;
MS 9EI) m/z: 244 9M1); IR 9KBr) 3480 cm21. Anal.
calcd for C10H13BrO2: C, 49.00, H, 5.35, Found. C, 48.88;
H, 5.18.
4.2.23. 1-Bromo-3-chloro-2-propanol *2w).6b 1H NMR
9CDCl3, 200 MHz) d 2.70 9brs, 1H), 3.55 9d, 2H,
Jˆ4.2 Hz), 3.65±3.75 9m, 2H), 3.95±4.05 9m, 1H); MS
9EI) m/z 171 9M1).
4.2.12. 1-Iodo-3-*4-methoxyphenyl)-2-propanol *2l). Pale
yellow liquid, 1H NMR 9CDCl3, 200 MHz) d 1.90 9brs, 1H),
2.85 9d, 2H, Jˆ6.2, 9.2 Hz), 3.25 9dd, 1H, Jˆ4.6, 9.2 Hz),
3.35 9dd, 1H, Jˆ3.8, 9.2 Hz), 3.60±3.75 9m, 1H), 3.80 9s,
3H), 6.85 9d, 2H, Jˆ8.2 Hz), 7.15 9d, 2H, Jˆ8.2 Hz); 13C
NMR 9CDCl3, 50 MHz) d 14.67, 41.66, 55.10, 71.62,
113.92, 128.98, 130.12, 158.25; MS 9EI) m/z: 292 9M1);
IR 9KBr) 3560 cm21. Anal. calcd for C10H13IO2: C, 41.12;
H, 4.49. Found: C, 41.18, H, 4.42.
4.2.24. 1-Chloro-3-iodo-2-propanol *2x).8 1H NMR
9CDCl3, 200 MHz) d 2.45 9brs, 1H), 3.30±3.45 9m, 2H),
3.60±3.70 9m, 2H), 3.72±3.85 9m, 1H); MS 9EI) m/z 220
9M1).
4.2.25. 1-Chloro-2-butanol *2y).8 1H NMR 9CDCl3,
200 MHz) d 0.95 9t, 3H, Jˆ7.1 Hz), 1.50±1.65 9m, 2H),
2.20 9brs, 1H), 3.35 9dd, 1H, Jˆ6.0, 7.1Hz), 3.55 9dd, 1H,
Jˆ3.6, 7.1 Hz), 4.10±4.20 9m, 1H); MS 9EI) m/z 108 9M1).
4.2.26. 1-Bromo-2-butanol *2z).6a 1H NMR 9CDCl3,
200 MHz) d 0.95 9t, 3H, Jˆ7.4 Hz), 1.50±1.60 9m, 2H),
2.20 9brs, 1H), 3.30±3.40 9m, 1H), 3.45±3.55 9m, 1H),
4.0±4.10 9m, 1H); MS 9EI) m/z 153 9M1).
4.2.13. 2-Chloro-1-phenylethanol *2m).8 1H NMR
9CDCl3, 200 MHz) d 2.50 9brs, 1H), 3.45±3.60 9m, 2H),
4.98 9dd, 1H, Jˆ3.6, 9.6 Hz), 7.25±7.45 9m, 5H); MS 9EI)
m/z: 156 9M1); IR 9KBr) 3460, 2935 cm21
.
4
4.2.14. 2-Bromo-1-phenylethanol *2n).1
H1 NMR
9CDCl3, 200 MHz) d 2.80 9brs, 1H), 3.45±3.65 9m, 2H),
4.90 9dd, 1H, Jˆ3.2, 9.4 Hz), 7.25±7.40 9m, 5H); MS 9EI)
m/z: 200 9M1); IR 9KBr) 3415, 2940 cm21
.
4.2.27. 1-Iodo-2-butanol *2z0).8 1H NMR 9CDCl3,
200 MHz) d 0.95 9t, 3H, Jˆ7.2 Hz), 1.55±1.70 9m, 2H),
3.05±3.25 9m, 1H), 3.30±3.50 9m, 1H), 3.75±3.80 9m,
1H); MS 9EI) m/z 200 9M1).
4
1
4.2.15. 2-Iodo-1-phenylethanol *2o).1 H NMR 9CDCl3,
200 MHz) d 2.50 9brs, 1H), 3.39±3.50 9m, 2H), 4.75 9m,
1H), 7.25±7.40 9m, 5H); MS 9EI) m/z: 248 9M1); IR 9KBr)
3398, 2930 cm21
.
Acknowledgements
5
1
4.2.16. 2-Chloro-1-*4-chlorophenyl) ethanol *2p).1
NMR 9CDCl3, 200 MHz) d 3.40±3.65 9m, 2H), 4.98 9m,
H
M. A. R. thanks CSIR, New Delhi, India for the award of a
fellowship.
1H), 7.25±7.40 9m, 4H); MS 9EI) m/z: 190 9M1); IR
9KBr) 3382, 2933 cm21
.
5
1
H
4.2.17. 2-Bromo-1-*4-chlorophenyl) ethanol *2q).1
References
NMR 9CDCl3, 200 MHz) d 2.50 9brs, 1H), 3.50±3.60 9m,
2H), 4.85 9m, 1H), 7.25±7.40 9m, 4H); MS 9EI) m/z: 234
1. For a review see: Bartlett, P. A. Asymmetric Synthesis;
Morrison, J. D., Ed.; Academic: Orlando, FL, 1984; Vol. 3,
p 411.
9M1); IR 9KBr) 3450, 2960 cm21
.
4.2.18. 2-Iodo-1-*4-chlorophenyl)ethanol *2r).1 6 1H NMR
9CDCl3, 200 MHz) d 2.45 9brs, 1H), 3.45±3.50 9m, 2H),
2. For reviews see: 9a) Moore, R. E. Marine Natural Products;
Scheuer, P. J., Ed.; Academic: New York, 1978; Vol. 1

6008
M. A. Reddy et al. / Tetrahedron 58 &2002) 6003±6008
Chapter 2. 9b). Fenical, W. Marine Natural Products; Scheuer,
P. J., Ed.; Academic: New York, 1980; Vol. 2, p 174.
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