Synthesis of fullerene oxides containing both 6,6-closed epoxide and 5,6-open ether moieties through thermolysis of fullerene peroxides

Article abstract of DOI:10.1021/jo9000977

Thermolysis of the fullerene hexaadduct C₆₀(OO ^tBu)₆ results in cleavage of two O-O bonds and elimination of two tert-butoxy groups to form two isomeric products with the formula C ₆₀(O)₂(OO^t

Full text of DOI:10.1021/jo9000977

to convert fullerenes into various fullerene oxides.2 In most cases
the 6,6-closed epoxides were produced. The first epoxide C70O
was isolated directly from fullerene soot by Diederich et al.3
Photooxidation of C60 generated the first C60 oxide C60O as the
only isolable product.4 Both of these two oxides were deter-
mined to be the epoxide isomer instead of the ether (oxaho-
mofullerene). Although theoretical calculations predicted the
ether isomer to be of comparable stability with the epoxide,5 it
remained unknown until 2001 when Weisman and co-workers
uncovered that photolysis and thermolysis of the ozonide C60(O3)
yields the ether and epoxide isomer, respectively.6 A closely
related oxahomofullerene derivative C60F18O was reported by
Taylor et al. in which the oxygen atom is inserted into a
fluorinated 5,6-junction.7 Contrary to pristine C60, the 6,6-
junction in multiple fullerene adducts can also be inserted with
an oxygen to form the ether structure.8
Synthesis of Fullerene Oxides Containing Both
6,6-Closed Epoxide and 5,6-Open Ether Moieties
through Thermolysis of Fullerene Peroxides
Jiayao Yao,† Dazhi Yang,† Zuo Xiao,† Liangbing Gan,*,†,‡
and Zheming Wang*,†
Beijing National Laboratory for Molecular Sciences, Key
Laboratory of Bioorganic Chemistry and Molecular
Engineering of the Ministry of Education, College of
Chemistry and Molecular Engineering, Peking UniVersity,
Beijing 100871, China, and State Key Laboratory of
Organometallic Chemistry, Shanghai Institute of Organic
Chemistry, Chinese Academy of Sciences, 354 Fenglin Lu,
Shanghai 200032, China
gan@pku.edu.cn; zmw@pku.edu.cn
Fullerene multioxides C60On can be readily produced through
classical oxidants such as m-chloroperoxybenzoic acid.2f,h These
multioxides are usually complex mixtures. Isolation and struc-
tural assignment are quite challenging. Electronic and 13C NMR
spectra were obtained for several triepoxides.9 The data suggest
that these epoxy groups are most likely located at adjacent
positions. Diannulene and epoxyannulene structures were
proposed as possible isomers for fullerene dioxide C60O2, but
their low yield and instability prevented full characterization.10
So far just one isomer of the dioxide C60O2 has been character-
ized by single-crystal X-ray analysis, which showed two epoxy
groups on the same hexagon.2f Here we report the preparation
and single-crystal X-ray structure of a fullerene derivative
containing an epoxy group at the 6,6-junction and an ether
moiety at the 5,6-junction.
ReceiVed January 15, 2009
Thermolysis of the fullerene hexaadduct C60(OOtBu)6 results
in cleavage of two O-O bonds and elimination of two tert-
butoxy groups to form two isomeric products with the
formula C60(O)2(OOtBu)4 in comparable yields. The two
oxygen atoms exist as two epoxy groups in one isomer 3,
and as an epoxy and an ether group in the other isomer 2.
Addition of hydroxylamine to 2 opens both the epoxy and
the ether moieties to give a cage-opened keto-ketoxime
derivative.
(3) Diederich, F.; Ettl, R.; Rubin, Y.; Whetten, R. L.; Beck, R.; Alvarez,
M.; Anz, S.; Sensharma, D.; Wudl, F.; Khemani, K. C.; Koch, A. Science 1991,
252, 548.
(4) Creegan, K. M.; Robbins, J. L.; Robbins, W. K.; Millar, J. M.; Sherwood,
R. D.; Tindall, P. J.; Cox, D. M.; Smith, A. B., III.; McCauley, J. P., Jr.; Jones,
D. R.; Gallagher, R. T. J. Am. Chem. Soc. 1992, 114, 1103.
(5) (a) Raghavachari, K. Chem. Phys. Lett. 1992, 195, 221. (b) Menon, M.;
Subbaswamy, K. R. Chem. Phys. Lett. 1993, 201, 321. (c) Wang, B.-C.; Chen,
L.; Chou, Y.-M. J. Mol. Struct. 1998, 422, 153. (d) Wang, B.-C.; Chen, L.; Lee
K.-J.; Cheng, C.-Y. J. Mol. Struct. 1999, 469, 127. (e) Manoharan, M. J. Org.
Chem. 2000, 65, 1093. (f) Huang, Y.-S.; Wang, G.-W. J. Mol. Struct.
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Fullerene oxides are among the most intensively studied
fullerene derivatives.1 A number of methods have been reported
(6) (a) Weisman, R. B.; Heymann, D.; Bachino, S. M. J. Am. Chem. Soc.
2001, 123, 9720. (b) Tsyboulski, D.; Heymann D.; Bachino, S. M.; Alemany
L. B.; Weisman, R. B. J. Am. Chem. Soc. 2004, 126, 7350.
(7) Boltalina, O. V.; Troshin, P. A.; de La Vaissiere, B.; Fowler, P. W.;
Sandall, J. P. B.; Hitchcock, P. B.; Taylor, R. J. Chem. Soc., Chem. Commun.
2000, 1325.
(8) Huang, S. H.; Xiao, Z.; Wang, F. D.; Zhou, J.; Yuan, G.; Zhang, S. W.;
ChenZ. F.; Thiel, W.; Schleyer, P. v. R.; Zhang, X.; Hu, X. Q.; Chen, B. C.;
Gan, L. B. Chem.sEur. J. 2005, 11, 5449.
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G.; Kappes, M. M. J. Chem. Phys. 1994, 101(4), 3243. (b) Fusco, C.; Seraglia,
R.; Lucchini, R. C. J. Org. Chem. 1999, 64, 8363. (c) Tajima, Y.; Takeuchi, K.
J. Org. Chem. 2002, 67, 1696.
(10) Heymann, D.; Bachilo, S. M.; Aronson, S. Fullerenes, Nanotubes Carbon
Nanostruct. 2005, 13, 73.
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Cheng, H.; Li, X. L.; Shang, G. J. Am. Chem. Soc. 2002, 124, 13384. (b) Gan,
L. B. Pure Appl. Chem. 2006, 78, 841. (c) Xiao, Z.; Yao, J. Y.; Yang, D. Z.;
Wang, F. D.; Huang, S. H.; Gan, L. B.; Jia, Z. S.; Jiang, Z. P.; Yang, X. B.;
Zheng, B.; Yuan, G.; Zhang, S. W.; Wang, Z. M. J. Am. Chem. Soc. 2007, 129,
16149. (d) Zhang, G. H.; Huang, S. H.; Xiao, Z.; Chen, Q.; Gan, L. B.; Wang,
Z. M. J. Am. Chem. Soc. 2008, 130, 12614.
† Peking University.
‡ Chinese Academy of Sciences.
(1) For review articles, see: (a) Heymann, D.; Weisman, R. B. C. R. Chim.
2006, 9, 1107. (b) Heymann, D. Fullerenes, Nanotubes Carbon Nanostruct. 2004,
12, 715. (c) Taylor, R. Proc. Electrochem. Soc. 1997, 97 (14), 281.
(2) (a) Wood, J. M.; Kahr, B.; Hoke, S. H., II.; Dejarme, L.; Cooks, R. G.;
Ben-Amotz, D. J. Am. Chem. Soc. 1991, 314, 5907. (b) Kalsbeck. W. A.; Thorp,
H. H. J. Electroanal. Chem. 1991, 314, 363. (c) Elemes, Y.; Silverman, S. K.;
Sheu, C.; Kao, M.; Foote, C. S.; Alvarez, M. M.; Whetten, R. L. Angew. Chem.,
Int. Ed. Engl. 1992, 31, 351. (d) Heymann, D.; Chibante, L. P. F. Chem. Phys.
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McElvany S. W.; Callahan J. H.; Ross M. M.; Lamb L. D.; Huffman, D. R.;
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3528 J. Org. Chem. 2009, 74, 3528–3531
10.1021/jo9000977 CCC: $40.75 2009 American Chemical Society
Published on Web 03/31/2009

SCHEME 1. Thermolysis of Fullerene-Mixed Peroxide
SCHEME 2. Possible Mechanism of the Thermolysis
In search of fullerene skeleton modification methods, we have
been investigating the chemistry of fullerene-mixed peroxides11
such as the hexa-adduct 1,11c which can be easily prepared from
tert-butylhydrogen peroxide and C60. To test its thermal stability,
we heated 1 in chlorobenzene. Two isomeric products were
isolated, namely epoxy ether 2 and the diepoxide 3 (Scheme
1). Addition of some C60 improves the selectivity of the
thermolysis, probably by trapping reactive decomposition spe-
cies. Heating isolated pure 2 or 3 could not lead to their
interconversion, instead giving a complicated mixture of
decomposition products. The diepoxide 3 is a known compound
that was synthesized by epoxidation of the monoepoxide
derivative C60(O)(OOtBu)4 with m-CPBA in our previous
report.12
SCHEME 3. Reactions of Compound 2
Scheme 2 shows a possible pathway for the thermolysis of
compound 1. Heating results in homolysis of the O-O bond
on the central pentagon, which is the most reactive site among
the six peroxo groups due to steric reasons. In our previous
study, we have shown that cleavage of the O-tBu bond on the
central pentagon is dominant under irradiation,11c which eventu-
ally leads to cage-opened compounds. In the second step, the
oxygen radical in A either inserts into an adjacent 5,6-junction
to form the pentadienyl radical B or adds to the diene moiety
to form the allyl radical C. Further cleavage of another O-O
bond from intermediates B and C produces compounds 2 and
3, respectively. The comparable yields of compounds 2 and 3
indicate that the two radical intermediates B and C have similar
stability. There is no product observed corresponding to
intermediate D. Insertion at the 6,6-junction of radical A is not
favorable because the steric strain would lift the oxygen-bound
carbon above the central pentagon, thus destabilizing the
cyclopentadienyl radical in D.
The presence of the ether moiety in compound 2 greatly
affects the reactivity of the epoxide group. Tris(pentafluorophe-
nyl)boron catalyzed the addition of water to 2 to form the acetal
4 (Scheme 3). Amino nucleophiles hydrazine and p-anisidine
added directly to form analogous aminoacetals 5a and 5b,
respectively. Addition of hydroxylamine resulted in the cage-
opened derivative 6, in which both the epoxide and ether
moieties were cleaved. Hydroxylamine probably attacks the
same ether carbon as in the formation of 4 and 5, but the
hydroxylaminoacetal is apparently not stable and rearranges into
the keto-ketoxime 6.
(12) Huang, S. H.; Xiao, Z.; Wang, F. D.; Gan, L. B.; Zhang, X.; Hu, X. Q.;
Zhang, S. W.; Lu, M. J.; Pan, J. Q.; Xu, L. J. Org. Chem. 2004, 69, 2442.
J. Org. Chem. Vol. 74, No. 9, 2009 3529

cage-opened fullerenes. Further work is in progress to prepare
cage-opened fullerene and heterofullerene derivatives by using
fullerene peroxides.
Experimental Section
All the reagents were used as received. Dichloromethane was
distilled over phosphorus pentaoxide. Other solvents were used as
received. Compound 1 was prepared according to the improved
procedure in ref 11c. Caution: Peroxides are potentially explosive
compounds, care must be taken to avoid possible explosion.
Compound 2. C60 (83 mg, 0.12 mmol) was added to a stirred
solution of compound 1 (290 mg, 0.23 mmol) in chlorobenzene
(97 mL) in the dark at 100 °C. After the mixture was stirred for 65
min, the solution was evaporated. The residue was chromatographed
on a silica gel column (30 mm × 50 mm) eluting with CH2Cl2/
CS2 (4:1). The first band was unreacted C60. The second band was
collected and evaporated to give compound 2 (52 mg, 0.047 mmol,
20%), and the third band was collected and evaporated to give
compound 3 (65 mg, 0.059 mmol, 25%).
1H NMR (400 MHz, CDCl3) δ 1.48 (18H), 1.41 (18H); 13C NMR
(100 MHz, CDCl3) all signals represent 2C except as noted, δ
168.99, 149.48, 148.70, 148.56, 148.40, 148.36, 148.06, 147.97
(1C), 147.70, 147.49, 147.44, 147.17, 146.72, 146.36, 146.24,
145.49 (1C), 145.12, 144.96, 144.25, 144.15, 142.97 (4C), 142.33,
142.21 (4C), 139.95, 138.93, 124.63, 90.51, 84.30, 82.37, 81.73,
67.66 (1C), 67.56 (1C), 26.57, 26.23; IR (microscope) 2798, 2923,
2850, 1363, 1193, 1015 cm-1; ESI-MS m/z (rel intensity) 1131 (100,
M + Na+); ESI-HRMS 1131.2237 calcd for C76H36NaO10 1131.2201.
Crystals of 2·CS2 suitable for X-ray diffraction were obtained
from slow evaporation in a mixture of CS2 and ethanol. Crystal
data: monoclinic, space group P21/c, a ) 18.9125(3) Å, b )
14.3843(2) Å, c ) 20.3313(4) Å, ꢀ ) 108.279(1)°, volume )
5251.9(2) Å3; final R indices [I > 2σ(I)] R1 ) 0.0586, wR2 ) 0.1429.
One of the four tert-butylperoxo groups is disordered into two
orientations (crystallographic data have been deposited in the
Cambridge Crystallographic Data Centre as deposition number
CCDC-652052).
Compound 4. Tris(pentafluorophenyl)borane (3 mg, 0.0059
mmol) was added to a stirred solution of compound 2 (27 mg, 0.024
mmol) in CH2Cl2 (10 mL) at 30 °C. After 10 min, the solution
was directly transferred onto a silica gel column (20 mm × 30
mm) and eluted with toluene/petroleum ether/AcOEt (10:10:1). The
first band was a trace amount of unreacted 2. The second band
was collected and evaporated to give compound 4 (15 mg, 0.013
mmol, 55%).
1H NMR (400 MHz, CDCl3) δ 5.68 (s, 1H), 3.62 (s, 1H), 1.45
(s, 18H), 1.41 (s, 9H), 1.33 (s, 9H); 13C NMR (100 MHz, CDCl3)
all signals represent 1C except as noted, δ 155.03, 149.73, 149.06,
148.99, 148.87, 148.60 (2C), 148.50, 148.45, 148.30, 148.24,
148.20, 147.91 (2C), 147.87 (2C), 147.83, 147.68, 147.61 (2C),
147.46, 147.06 (2C), 146.93, 143.86, 146.38, 146.26, 146.20,
145.71, 145.61, 145.43, 145.15, 145.01, 144.80, 144.69, 144.65,
144.51, 144.41, 144.10, 144.02, 143.71, 143.25, 143.17, 143.15,
142.91, 142.39, 140.46, 140.44, 139.39, 138.88, 137.93, 133.26,
125.61, 122.88, 105.83, 94.19, 92.62, 84.02, 82.76, 82.10, 82.06,
82.03, 80.62, 72.60, 26.87, 26.81, 26.67, 26.64; FT-IR (microscope)
3397 (broad), 2977, 2926, 2854, 1364, 1241, 1191, 1102, 1087,
1060 cm-1; ESI-MS m/z (rel intensity) 1149 (100, M + Na+); ESI-
HRMS 1149.2338, calcd for C76H38NaO11 1149.2306.
Compound 5a. N2H4 ·H2O (85%) (1 µL) was added to a stirred
solution of compound 2 (25 mg, 0.023mmol) in CH2Cl2 (6 mL).
After 1 min, the solution was directly transferred to a silica gel
column (20 mm × 30 mm) and eluted with toluene/petroleum ether/
AcOEt (10:10:1). The first band was a trace amount of unreacted
2. The elutent was then changed to toluene/petroleum ether/AcOEt
(5:5:1). The second band was collected and evaporated to give
compound 5a (18 mg, 0.016 mmol, 70%).
FIGURE 1. Structure of compounds 2 (above) and 6 (below). For
clarity hydrogen atoms on the tert-butyl groups were omitted. The
structure of 6 has a position exchange disorder involving the carbonyl
and the ketooxime group. Color scheme: gray C, red O, blue N, and
green H.
Spectroscopic data are in agreement with the structures
depicted in Schemes 1 and 3. The epoxy ether 2 has Cs
symmetry. Its pyran sp2 carbons appeared at 167.0 and 124.6
ppm, which are quite different from other sp2 carbons on the
cage ranging from 138.9 to 149.5 ppm. The two sp3 epoxy
carbons appear at 67.7 and 67.6 ppm. The presence of the acetal
moiety was deduced from the unique signal at 105.8, 103.1,
and 97.4 ppm for compounds 4, 5a, and 5b, respectively. This
acetal carbon showed relatively higher intensity due to the NOE
of OH or NH proton, a common phenomenon observed before
for other fullerene acetal moieties.8 The keto-ketoxime 6 showed
a carbonyl peak at 190.4 ppm. The hydrogen in 6 appeared at
1
6.26 ppm as a sharp signal on the H NMR spectrum, and its
corresponding carbon appeared at 39.7 ppm on the 13C NMR
spectrum. But the location of the hydrogen in 6 could not be
identified from these NMR data. The hydrogen could be adjacent
to the ketoxime group as shown in Scheme 3 or adjacent to the
carbonyl group. A disorder in the X-ray structure of 6 prevented
us from distinguishing the two possible structures (see below).
Single-crystal X-ray structures were determined for com-
pounds 2 and 6 as shown in Figure 1. The pyran moiety in 2
adopts a distorted boat conformation. The ether oxygen at the
5,6-junction is tilted toward the 6-membered ring. The distance
between the two carbons bonded to the ether oxygen is 2.228
Å. The epoxide C-C bond length is 1.524 Å. Double bonds
on the pyran ring are the shortest on the cage (1.324 and 1.333
Å). The structure of 6 is disordered in the cage-opened region.
The presence of the ketooxime and carbonyl groups is clearly
observed, but the two groups are disordered in the two positions.
Therefore it is impossible to determine which one is adjacent
to the H-bound sp3 carbon. The structure shown in Figure 1
represents one of the possible structures. The distance between
the carbonyl and ketooxime carbons is 2.768 Å.
In summary, thermolysis of fullerene peroxide was found to
induce homolysis of the O-O bond. The resulting fullerene-
bound oxygen radical forms either an epoxy or an ether moiety
at the same 5,6-junction, which could serve as a precursor for
3530 J. Org. Chem. Vol. 74, No. 9, 2009

1H NMR (400 MHz, CDCl3) δ 5.21 (s, 1H), 3.66 (s, 1H), 1.47
(s, 9H), 1.45 (s, 9H), 1.43 (s, 9H), 1.25 (s, 9H); 13C NMR (100
MHz, CDCl3) all signals represent 1C except as noted, δ 155.54,
149.81, 149.05, 148.96, 148.84, 148.62, 148.51, 148.50, 148.35
(2C), 148.28, 148.25 (2C), 148.17, 147.95, 147.87, 147.81, 147.78,
147.68, 147.46, 147.14, 147.08, 147.06, 146.87, 146.44, 146.42,
146.28 (2C), 145.80, 145.76, 145.52, 145.35, 145.26, 145.15,
144.79, 144. 69 (2C), 144.37, 144.03, 143.96, 143.80, 143.29,
143.16, 143.07, 142.52, 142.22, 142.20, 140.55, 140.19, 139.45,
138.09, 132.47, 124.49, 121.96, 103.10, 94.50, 93.14, 84.05, 82.99,
82.14, 82.05, 81.96, 80.84, 72.54, 26.97, 26.83, 26.69, 26.66; FT-
IR (microscope) 3534, 3375, 2978, 2977, 1365, 1258, 1241, 1191,
1089, 1056, 1021, 805 cm-1; ESI-MS m/z (rel intensity) 1141 (97,
M + H+); ESI-HRMS did not show molecular ion signal.
Compound 5b. p-anisidine (300 mg, 2.42 mmol) was added to
a stirred solution of compound 2 (42 mg, 0.038 mmol) in toluene
(5 mL) at 50 °C. After 50 min, the solution was directly transferred
onto a silica gel column (20 mm × 30 mm) and eluted with toluene/
petroleum ether/AcOEt (10:10:1). The first band was a trace amount
of unreacted 2. The second band was collected and evaporated to
give compound 5b (29 mg, 0.024 mmol, 62%).
min, the solution was directly transferred onto a silica gel column
(20 mm × 30 mm) and eluted with toluene/petroleum ether/AcOEt
(10:10:1). The first band was a trace amount of unreacted 2. The
elutent was then changed to toluene/petroleum ether/AcOEt (5:5:
1). The second band was collected and evaporated to give compound
6 (6 mg, 0.0053 mmol, 58%).
1H NMR (400 MHz, CDCl3) δ 6.26 (s, 1H), 3.9 (broad, 1H),
1.43 (s, 9H), 1.37 (s, 9H), 1.34 (s, 9H), 1.31 (s, 9H); 13C NMR
(100 MHz, CDCl3) all signals represent 1C except as noted, δ
190.21, 150.42, 149.54, 149.33, 149.20, 149.13, 149.03, 148.93,
148.88, 148.81, 148.72, 148.69, 148.61 (2C), 148.60, 148.48,
148.41, 148.37, 148.21, 148.09, 148.08, 147.97, 147.70, 147.55,
147.14, 146.47, 145.84, 144.96, 144.82, 144.77, 144.75, 144.73,
144.68, 144.65, 144.38, 144.29, 144.25, 144.04, 143.84, 143.58,
143.09, 142.56 (2C), 142.05, 141.50, 141.19, 140.66, 140.56,
140.08, 139.70, 137.08, 134.65, 134.62, 91.15, 88.42, 87.15, 85.68,
82.74, 81.97, 81.68, 81.48, 73.67, 39.63, 26.95 (3C), 26.72 (9C);
FT-IR (microscope) 3525, 3320, 2978, 2928, 1730, 1456, 1388,
1365, 1191, 1065, 1010, 733 cm-1; ESI-MS m/z (rel intensity) 1164
(100, M + Na+); ESI-HRMS 1142.2616, calcd for C76H40NO11
1142.2596.
1H NMR (400 MHz, CDCl3) δ 7.49-7.47 (d, 2H), 6.99-6.97
(d, 2H), 6.04 (s, 1H), 3.88 (s, 3H), 3.66 (s, 1H), 1.48 (s, 9H), 1.37
(s, 9H), 1.33 (s, 9H), 1.11 (s, 9H); 13C NMR (100 MHz, CDCl3)
all signals represent 1C except as noted, δ 155.94, 154.18, 149.75,
149.03, 148.98, 148.80, 148.62, 148.48, 148.47, 148.35, 148.28,
148.23 (3C), 148.18 (3C), 147.87, 147.82, 147.81, 147.60, 147.45,
147.39, 147.08, 147.05 (2C), 146.47, 146.31, 145.78 (2C), 145.65,
145.53, 145.47, 145.26, 145.19, 144.77, 144.50 (2C), 144.34,
144.17, 143.97, 143.95, 143.31, 143.26, 143.17, 142.98, 142.14,
141.29, 140.23, 140.15, 139.34, 138.19, 137.19, 132.77, 124.64,
122.03, 121.59, 114.12, 114.04, 97.38, 96.20, 93.36, 84.38, 82.08,
82.06, 81.90, 81.55, 80.58, 72.56, 55.77, 26.90, 26.66, 26.55, 26.40;
FT-IR (microscope) 3535, 2978, 2931, 1512, 1365, 1244, 1191,
1086, 1054, 1022, 872 cm-1; ESI-MS m/z (rel intensity) 1232 (100,
M + H+); ESI-HRMS did not show molecular ion signal.
Crystals of 6·5H2O·3CDCl3 suitable for X-ray diffraction were
obtained from slow evaporation in CDCl3 in the NMR tube. Crystal
data: monoclinic, space group P 21/c, a ) 13.9150(2) Å, b )
25.7935(4) Å, c ) 22.4441(4) Å, ꢀ ) 117.0560(10)°, volume )
7174.0(2) Å3; final R indices [I > 2σ(I)] R1 ) 0.1066, wR2 ) 0.3136
(crystallographic data have been deposited in the Cambridge
Crystallographic Data Centre as deposition number CCDC-716211).
Acknowledgment. This work is supported by NNSFC
(Grants 20632010, 20821062, and 20772004) and the Major
State Basic Research Development Program (2006CB806201).
Supporting Information Available: Selected spectroscopic
data for all the new compounds and crystallographic data for 2
and 6. This material is available free of charge via the Internet
at http://pubs.acs.org.
Compound 6. To a stirred solution of compound 2 (10 mg,
0.0090 mmol) in CH2Cl2 (3 mL) was added a solution of
NH2OH·HCl (3.48 mg, 0.05 mmol) and K2CO3 (3.45 mg, 0.025
mmol) dissolved in 50 µL of water at room temperature. After 12
JO9000977
J. Org. Chem. Vol. 74, No. 9, 2009 3531