Regio- and diastereoselective ring-opening reaction of epoxides with nitric oxide

Article abstract of DOI:10.1080/00397910600908769

Ring-opening reactions of epoxides with nitric oxide afforded syn or anti α-hydroxy nitrates in high regio- and diastereoselectivities in good yields. Copyright Taylor & Francis Group, LLC.

Full text of DOI:10.1080/00397910600908769

Synthetic Communicationsw, 36: 3149–3152, 2006
Copyright # Taylor & Francis Group, LLC
ISSN 0039-7911 print/1532-2432 online
DOI: 10.1080/00397910600908769
Regio- and Diastereoselective Ring-Opening
Reaction of Epoxides with Nitric Oxide
Yuan Fan and Xiaojie Shang
State Key Laboratory of Applied Organic Chemistry,
Lanzhou University, Lanzhou, Gansu, China
Zhongquan Liu
State Key Laboratory of Applied Organic Chemistry,
Lanzhou University, Lanzhou, Gansu, China and Academy
of Organic Chemistry, GanNan Teachers’ College,
Ganzhou, Jiangxi, China
Longmin Wu
State Key Laboratory of Applied Organic Chemistry,
Lanzhou University, Lanzhou, Gansu, China
Abstract: Ring-opening reactions of epoxides with nitric oxide afforded syn or anti
a-hydroxy nitrates in high regio- and diastereoselectivities in good yields.
Keywords: Epoxide, nitric oxide, ring opening
The three-membered ring of epoxides is an important kind of functional
group.[1] Ring strain renders epoxides susceptible to ring-opening reactions.
This ring-opening behavior makes epoxides useful synthetic intermediates,
which fully deserve a prominent place in the arsenal of organic chemists.
Epoxides are thereby widely employed in organic synthesis. New approaches
have continuously emerged for the stereoselectivity of ring-opening
reactions.[2] Among them, ring-opening reactions of epoxides by radicals
Received in R.O.C. February 7, 2006
Address correspondence to Longmin Wu, State Key Laboratory of Applied Organic
Chemistry, Lanzhou University, Lanzhou, Gansu 730000, China. E-mail: nlaoc@lzu.
edu.cn
3149

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Y. Fan et al.
are particularly interesting.[3] We have found that the three-membered ring of
aziridines and a,b-epoxy phenyl ketones can be efficiently cleaved by NO in
high regio- and diastereoselectivities.[4] In particular, the ring-opening
reaction of a,b-epoxy phenyl ketones with NO regioselectively afforded the
C-3 ring-opened products in a highly syn-selective manner.[4c] As part of
our ongoing research project on nitric oxide (NO), further study has been
carried out to extend the substrate scope to other epoxides that have no neigh-
boring carbonyl group. The ring-opening reaction occurred regioselectively at
C-3, however, with an anti-selectivity to afford single anti a-hydroxy nitrates
in good yield. It seems that the syn- or anti-selective ring-opening patterns of
epoxides strongly depend on the substituent attached to the C-2 atom
(Scheme 1).
When a-hydroxy epoxides were used as substrates, anti a-hydroxy
nitrates were still obtained, in which the two neighboring hydroxy groups
were on the syn position. In addition, ring-opened products of cyclic
epoxides also led us to suggest that the two functional groups were newly
formed at the opposite sides of the ring. It was clear that the ring-opening
reaction of epoxides with NO gave anti a-hydroxy nitrates, which is
different from those of a,b-epoxyketones with NO, which gave only syn
products. The difference between a-carbonyl epoxides and noncarbonyl sub-
stituted epoxides with NO in the ring opening suggested that the carbonyl
group was a key factor in the reaction and the mechanisms or intermediates
of those were different.
EXPERIMENTAL
The reaction procedure was performed as previously described.[4] In a represen-
tative experiment, freshly prepared NO gas bubbled through the well-stirred 15-
mL CH2Cl2 solution of 1a (1 mmol). The reaction completed in ca. 10 h.
Isolation and purification with column chromatography yielded the product
2a (222.5 mg, 98%). The products were characterized by HRMS, fast atom
1
bombardment mass spectrometer (FAB-MS), and H and 13C NMR spec-
troscopy. High-resolution mass spectrometer (HRMS): Bruker Daltonics
Apex II FT-ICR; FAB: VG ZAB-HS; Bruker Apex II; NMR: 13C: 100 MHz,
Scheme 1.

Regio- and Diastereoselective Ring Opening Reaction of Epoxides
3151
1H: 400 MHz, Varian Mecury 400 (TMS). 2a: HRMS m/z 477.1495 (calcd. for
1
C10H13NO5 [2M þ Na]þ, 477.1485, error ¼ 2.0 ppm); H NMR (400 MHz,
CDCl3): d 7.425 (5H, s), 5.977 (1H, d, J ¼ 8.4 Hz), 3.744 (1H, m,
J ¼ 8.4 Hz, J ¼ 5.2 Hz, J ¼ 2.0 Hz, J ¼ 1.6 Hz), 3.507 (1H, t, J ¼ 6.4 Hz),
2.657 (1H, d, J ¼ 4.8 Hz), 1.909 (1H, d, J ¼ 8.0 Hz), 1.224 (3H, d,
J ¼ 6.4 Hz); 13C NMR (100 MHz, CDCl3): d 134.7, 129.5, 129.0, 127.4,
Table 1. Ring-opening reaction of epoxides with NO in CH2Cl2 at ambient tempera-
ture
Entry
1
Epoxidea
Productb
RT (h)c Yield (%)d
1a
1b
1c
1d
1e
2a
2b
2c
2d
2e
10
10
12
12
12
98
90
82
81
83
2
3
4
5
6
7
1f
2f
12
12
85
80
1g
2g
aEpoxides having a chiral center are racemic isomers.
bProducts are the corresponding racemic isomers.
cReaction time.
dIsolated yields after column chromatography.

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Y. Fan et al.
1
86.8, 75.6, 66.0, 20.4; 2f: FAB: m/z 162.1 [M þ 1]þ; H NMR (400 MHz,
CDCl3): d 4.809 (1H, m, J ¼ 12.8 Hz, J ¼ 9.6 Hz, J ¼ 4.4 Hz), 3.675 (1H,
m, J ¼ 10.8 Hz, J ¼ 8.8 Hz, J ¼ 4.8 Hz, J ¼ 2.0 Hz), 2.430 (1H, s), 2.190
(1H, m), 2.174 (1H, m), 1.830 (2H, m), 1.447 (4H, m); 13C NMR (100 MHz,
CDCl3): d 87.2, 70.5, 33.0, 28.7, 23.7, 23.4; 2g: HRMS m/z 379.2084 (calcd.
1
for C8H15NO4 [2M þ H]þ, 379.2075, error ¼ 2.4 ppm); H NMR (400 MHz,
CDCl3): d 5.190 (1H, m, J ¼ 8.8 Hz, J ¼ 7.6 Hz, J ¼ 7.2 Hz), 3.903 (1H, m,
J ¼ 9.2 Hz, J ¼ 7.2 Hz, J ¼ 6.8 Hz, J ¼ 2.4 Hz), 2.380 (1H, s), 1.919
(8H, m), 1.585 (4H, m); 13C NMR (100 MHz, CDCl3): d 89.6, 71.4, 30.3,
29.0, 26.0, 25.2, 25.1, 22.5.
The reaction of the epoxide 1 with NO afforded the corresponding anti
a-hydroxy nitrates compound 2 in good yields. The coupling constant of
the vicinal hydrogen atoms is the distinct difference in the ring-opened
products anti and syn a-hydroxy nitrates. In the former, the datum is ca.
8.4 ppm, whereas it is 3.6 Hz in the latter. The results are collected in Table 1.
In conclusion, this work reports a novel ring-opening method for
epoxides. The ring-opening reaction of non-vicinal-carbonyl substituted
epoxides with NO produced anti a-hydroxy nitrates in high regioselectivity
in good to excellent yields.
ACKNOWLEDGMENT
We thank the National Natural Science Foundation of China (Grant No.
20272022) for financial support.
REFERENCES
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Acc. Chem. Res. 2004, 37, 497–505; (b) Benjamin, S. L.; Kevin, B. Metal-catalyzed
epoxidations of alkenes with hydrogen peroxide. Chem. Rev. 2002, 103,
2457–2473.
2. For review, see Jacobsen, E. N. Asymmetric catalysis of epoxide ring-opening
reactions. Acc. Chem. Res. 2000, 33, 421–431.
¨
3. For reviews, see Gansauer, A.; Lauterbach, T.; Narayan, S. Strained heterocycles in
radical chemistry. Angew. Chem. Int. Ed. 2003, 42, 5556–5573.
4. (a) Liu, Z.-Q.; Fan, Y.; Li, R.; Zhou, B.; Wu, L.-M. Regio- and stereoselective ring-
opening of aziridines with nitric oxide. Tetrahedron Lett. 2005, 46, 1023–1025;
(b) Liu, Z.; Zhou, B.; Liu, Z.; Wu, L. Electrophilic reaction of nitric oxide with
Wittig reagents. Tetrahedron Lett. 2005, 46, 1095–1097; (c) Liu, Z.; Li, R.;
Yang, D.; Wu, L. Ring-opening of 2,3-epoxy phenyl ketones upon reaction with
nitric oxide. Tetrahedron Lett. 2004, 45, 1565–1566.