Facile preparation of fullerenyl boronic esters

Article abstract of DOI:10.1016/j.tet.2012.03.092

The fullerendiol C₆₀(OH)₂(OOt-Bu)₄ 1 reacts with various arylboronic acids ArB(OH)₂ to form fullerene-containing boronic esters C₆₀(O₂BAr)(OOt-Bu) ₄ in up to 95% yield depending on the structure of aryl group. Bis(pinacolato)diboron (B(OCMe₂)₂)₂ also reacts with 1 to form C₆₀(O₂BB(OCMe₂) ₂)(OOt-Bu)₄. The bisboronic ester C₆₀(O)(O ₂BAr)₂(OOt-Bu)₂ was also obtained starting from a tetrahydroxyl fullerene derivative C₆₀(O)(OH)₄(OOt-Bu) ₂. The fullerenyl boronic esters are moderately stable in air. Single crystal X-ray structure of C₆₀(O₂BPh)(OOt-Bu)₄ was obtained.

Full text of DOI:10.1016/j.tet.2012.03.092

Tetrahedron 68 (2012) 5193e5196
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Facile preparation of fullerenyl boronic esters
,b,
Zhifei Dai a, Zhongping Jiang a, Gang Zhang a, Nana Xin a, Liangbing Gan a
*
a 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
b State Key Laboratory of Organometallic Chemistry, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, 354 Fenglin Lu, Shanghai 200032, China
a r t i c l e i n f o
a b s t r a c t
Article history:
The fullerendiol C60(OH)2(OOt-Bu)4 1 reacts with various arylboronic acids ArB(OH)2 to form fullerene-
containing boronic esters C60(O2BAr)(OOt-Bu)4 in up to 95% yield depending on the structure of aryl
group. Bis(pinacolato)diboron (B(OCMe2)2)2 also reacts with 1 to form C60(O2BB(OCMe2)2)(OOt-Bu)4. The
bisboronic ester C60(O)(O2BAr)2(OOt-Bu)2 was also obtained starting from a tetrahydroxyl fullerene
derivative C60(O)(OH)4(OOt-Bu)2. The fullerenyl boronic esters are moderately stable in air. Single crystal
X-ray structure of C60(O2BPh)(OOt-Bu)4 was obtained.
Received 9 February 2012
Received in revised form 17 March 2012
Accepted 22 March 2012
Available online 29 March 2012
Keywords:
Fullerene
Ó 2012 Elsevier Ltd. All rights reserved.
Boronic ester
Boronic acid
Peroxide
Ferrocene
1. Introduction
2. Results and discussion
Numerous fullerene derivatives have been prepared over the
past twenty years.1 Introduction of a suitable addend has limited
Boronic esters are widely used in SuzukieMiyaura coupling
reactions.18 They are readily prepared from boronic acid and alco-
hol. Vicinal diol esters of alkyl and arylboronic acids, such as pinacol
esters are particularly useful because of their enhanced stability.
We have reported the fullerene diol 1 through Lewis acid catalyzed
hydrolysis of the epoxide precursor C60(O)(OOt-Bu)4.19 In an at-
tempt to prepare fullerene-containing boronic esters, we treated 1
with phenylboric acid. The reaction was quite efficient giving the
boronic ester 2 in excellent yield after stirring at rt for 50 min
(Scheme 1).
effect on the
p conjugation and cage structure, yet can greatly
enhance the solubility in organic solvents or water.2 Thus fullerene
derivatives exhibit improved functional properties in many cases
compared to the pristine fullerene.3 For example, the best known
material in fullerene based solar cell is a C60 derivative,4 namely
PCBM prepared by addition of an azo compound to C60 followed by
extrusion of nitrogen under heating.
Among all the reported fullerene derivatives, methano-5 and
pyrrolidinofullerenes6 are the most intensively investigated ful-
lerene derivatives because of their easy preparation procedure and
good stability. Other fullerene derivatives include epimino-,7 ep-
oxy-,8 pyrazolino-,9 lactono-,10 isoquinolino-,11 and various [4þ2]
DielseAlder adducts.12 Methods are still being developed in the
literature for the preparation of new fullerene derivatives.13 To the
best of our knowledge, fullerene-containing boronic esters remain
unknown.14 We have reported the preparation of fullerene-mixed
peroxides.15 Further investigations have led to a number of cage
skeleton modified fullerene derivatives, such as open-cage16 and
azafullerenes.17 Here we report the preparation of fullerenyl bo-
ronic esters through reaction of fullerenol with arylboronic acid.
* Corresponding author. Tel.: þ86 10 62753427; fax: þ86 10 62751708; e-mail
Scheme 1. Formation of fullerenyl boronic esters.
address: gan@pku.edu.cn (L. Gan).
0040-4020/$ e see front matter Ó 2012 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2012.03.092

5194
Z. Dai et al. / Tetrahedron 68 (2012) 5193e5196
The boronic esterification reaction can be extended to other
can be stored for weeks with little change. In our previous study, we
have reported the preparation of 8 through treatment of the epoxide
precursor C60(O)(OOt-Bu)4 with BF3 in the presence of moisture.14
boronic acids as shown in Scheme 1. Furan-2-ylboronic acids gave
good yields, but the thiophen-2-ylboronic acid afforded the corre-
sponding ester in only 25% yield. The major products of the thio-
phen-2-ylboronic acid reaction with 1 are complex mixtures.
Reduction of the peroxo groups in 1 by the thiophen-2-ylboronic
acid and subsequent reactions may be responsible for the forma-
tion of complex byproducts and low yield of 2d. In the reaction with
ferrocenylboronic acid, a byproduct 4 was also obtained (Scheme 2).
Apparently compound 4 was produced from decomposition of the
ferrocenyl moiety.20 The cyclopentadienylboric ester 4 is less polar
than the ferrocenylboronic ester 3 and eluted as the first band on
silica gel column.
Scheme 4. Decomposition of fullerenyl boronic esters.
Spectroscopic data are in agreement with the structures
depicted in the Schemes. All the new compounds showed Cs sym-
metry on the NMR spectra. For compounds 2e5, there are two
singlet signals for the four tert-butylperoxo groups on the 1H NMR
spectra. On the 13C NMR spectra, the 54 sp2 fullerene cage carbons
appeared as 28 signals, two of which are half intensity corre-
sponding to the two unique carbons on the mirror plane. Com-
pounds 7a and 7b are slightly different in that they have 52 sp2
fullerene cage carbons. The HRMS also showed the expected mo-
lecular ion signals.
To further confirm the structural assignment, we obtained the
single crystal X-ray structure for compound 2a (Fig. 1). Suitable
single crystals were obtained from slow evaporation of a mixture
solution CS2/CHCl3/MeOH. The structure indicates the phenyl ring
is almost coplanar with the dioxaborolane ring. The dihedral angle
between the two planes is 5.9ꢀ. The CeC bond of the dioxaborolane
ꢀ
ring is the longest at 1.57 A. Double bonds on the cyclopentadiene
ꢀ
ring are the shortest on the cage (1.33 and 1.34 A).
Scheme 2. Reactions with ferrocenylboronic acid and bis(pinacolato)diboron.
The bis(pinacolato)diboron also reacted with 1 smoothly at rt in
dichloromethane (Scheme2). Asabove no catalystwasneededfor the
transesterification process. Attempts to replace the second pinacol
moiety with 1 failed probably due to steric hindrance. The presenceof
the four tert-butylperoxo groups makes the dumbbell product too
crowded. After the successful reactions with the fullerene diol 1, we
then treated the fullerenol 621 with four hydroxyl groups with bo-
ronic acids, and obtained the fullerene bisboronic esters 7 (Scheme 3).
The yields of compounds 7 are comparable to the diol derivatives 2.
Fig. 1. X-ray structure of 2a. For clarity hydrogen atoms are not shown. Ellipsoids were
drawn at 50% level. Grey-carbon, red-oxygen, purple-boron.
In summary, fullerene-containing boronic esters have been
prepared through the reaction between vicinal fullerendiol and
arylboronic acid. Yields of the reactions range from moderate to
excellent depending on the structure of the aryl group. Preliminary
tests indicate that the fullerenyl boronic esters are reactive towards
various reagents. Potential applications of fullerenyl boronic esters
may include protection of hydroxyl groups in fullerene derivatives
and coupling reagents in SuzukieMiyaura reaction.
3. Experimental section
3.1. General
Scheme 3. Formation of fullerenyl bisboronic esters.
Compared to the analogous 1,3-dioxolane fullerene deriva-
tives,14a,22 the fullerenyl boronic esters are moderately stable. Upon
storage in air for one week, the borate 8 could be detected
(Scheme 4). Under nitrogen atmosphere, the fullerenyl boronic esters
All reagents were used as received. Dichloromethane (DCM) was
distilled from phosphorus pentoxide. Chloroform was treated with

Z. Dai et al. / Tetrahedron 68 (2012) 5193e5196
5195
concentrated H2SO4, washed with water to remove ethanol, and
dried with anhydrous K2CO3. Other solvents were used as received.
The reactions were carried out in air. The NMR spectra were
obtained at 25 ꢀC unless noted. Compounds 119 and 621 were pre-
pared as reported before.
7.67 (d, J¼8.80 Hz, 1H), 7.61 (s, 1H), 7.43 (t, J¼7.30 Hz, 1H), 7.31 (t,
J¼3.86 Hz, 1H), 1.50 (s, 18H), 1.20 (s, 18H). 13C NMR: (CDCl3,
100 MHz, all signals represent 2C except noted):
d 150.86, 149.70,
149.16, 148.68, 148.34, 148.31 (1C), 148.17, 148.12, 147.61, 147.34,
147.30 (1C), 147.28, 146.92, 145.63, 145.31, 145.27, 145.25, 145.17,
144.87, 144.47, 144.20, 143.81, 143.51, 143.34, 142.99, 141.20, 139.69,
127.32, 126.38, 122.94, 122.16, 121.06, 112.07, 91.49 (1C), 85.23 (1C),
82.27, 82.03 (4C-(CH3)3), 80.87, 26.76 (6CH3), 26.53 (6CH3). FT-IR
(microscope): 2979, 2928, 2854, 1592, 1568, 1474, 1387, 1364,
1331, 1314, 1294, 1258, 1243, 1192, 1167, 1143, 1121, 1105, 1092, 1072,
1042, 1023, 1005 cmꢁ1. ESI-HRMS (m/z): C84H45BNO11 (MþNHþ4 ),
calculated: 1254.3093 found: 1254.3097.
3.2. Caution
A large amount of peroxides is involved in some of the reactions.
Care must be taken to avoid possible explosion.
3.2.1. Compound 2a. To
a solution of compound 1 (100 mg,
0.09 mmol) in DCM (20 mL) was added phenylboronic acid (55 mg,
0.45 mmol). The resulting solution was stirred at rt in dark for 50 min.
The solution was chromatographed on silica gel eluting with toluene
to yield the compound 2a as an orange solid (103 mg, 94%). 1H NMR
3.2.5. Compound 2d. To
a solution of compound 1 (32 mg,
0.029 mmol) in DCM (10 mL) was added 2-thiophenylboronic acid
(8.2 mg, 0.064 mmol). The resulting solution was stirred at rt in dark
for 50 min. The solution was chromatographed on silica gel eluting
with toluene/petroleum ether (bp 60e90 ꢀC) (1:1) to yield the
compound 2d as an orange solid (8.7 mg, 25%). 1H NMR (CDCl3,
(300 MHz, CDCl3):
18H), 1.17 (s, 18H). 13C NMR: (CDCl3, 75 MHz, all signals represent 2C
except noted): 151.23, 150.14, 149.24, 149.21, 148.75, 148.39 (3C),
d 8.00e8.06 (m, 2H), 7.40e7.60 (m, 3H), 1.52 (s,
d
148.25, 148.11, 147.66, 147.40, 147.36 (4C), 147.01, 145.95, 145.74,
145.44 (4C), 145.21, 144.98, 144.57, 144.30, 143.85, 143.57, 143.30,
143.12,141.30, 139.59,135.35,131.90,127.87, 91.50, 85.18, 82.37, 82.04,
81.87, 80.86, 26.71 (6CH3), 26.53 ppm (6CH3); FT-IR (microscope):
2980, 2931, 2870, 1393, 1361, 1192, 1095, 1026, 1008, 871, 757,
698 cmꢁ1; ESI-MS: (m/z, %): 1214 (100) (MþNHþ4 ), 1235 (30) (MþK)þ.
400 MHz):
1H), 1.50 (s, 18H), 1.20 (s, 18H). 13C NMR: (CDCl3, 100 MHz, all signals
represent 2C except noted): 151.03, 149.99, 149.17, 149.14, 148.68,
d
7.89 (d, J¼3.08 Hz, 1H), 7.75 (d, J¼4.56 Hz, 1H), 7.28 (m,
d
148.33, 148.31(1C), 148.19, 148.07, 147.60, 147.34, 147.33 (1C), 147.29,
146.94, 145.70, 145.66, 145.35, 145.32, 145.17, 144.90, 144.48, 144.23,
143.78, 143.50, 143.27, 143.05, 141.23, 139.57, 138.53, 133.49 (1C),
128.28 (1C), 91.43 (1C), 85.16 (1C), 82.34, 82.05 (C-(CH3)3), 81.90 (C-
(CH3)3), 80.88, 26.76 (6CH3), 26.51 (6CH3). FT-IR (microscope): 2979,
2924, 2852,1523,1464,1426,1386,1364,1314,1288,1261,1231,1193,
1142, 1121, 1105, 1092, 1059, 1037, 1024, 1004 cmꢁ1. ESI-HRMS (m/z):
C80H43BNO10S (MþNHþ4 ) calculated: 1220.2708, found: 1220.2713.
3.2.2. Crystal data for compound 2a. C83H42BCl3O10, T¼123(2) K,
Monoclinic, space group P2(1)/n, Unit cell dimensions:
3
ꢀ
ꢀ
ꢀ
ꢀ
a¼15.234(3) A, b¼15.951(3) A, c¼23.808(5) A, V¼5740(2) A . Z¼4,
rcalcd¼1.523 Mg/m3. Reflections collected/unique 53,676/13,141
[R(int)¼0.05564]. Final R indices [I>2 (I)] R1¼0.0672, wR2¼0.1904.
s
CCDC 703261.
3.2.6. Compound 3. To a solution of compound 1(305 mg, 0.27 mmol)
in DCM (65 mL) was added ferrocenylboronic acid (253 mg,1.1 mmol).
The resulting solutionwas stirred at rt in dark for 10 h. The solvent was
evaporated. The residue was dissolved in about 5 mL CHCl3 and pre-
cipitated by adding methanol. The process was repeated three times to
remove unreacted ferrocenylboronic acid. The solid was then chro-
matographed on silica gel eluting with toluene/petroleum ether (bp
60e90 ꢀC) (1:1) to yield the first band as compound 3 (orange solid,
247 mg, 69%), the second red band was eluted as compound 4 (orange
solid, 54 mg, 17%). Characterization data for compound 3: 1H NMR
3.2.3. Compound 2b. To
a solution of compound 1 (85 mg,
0.077 mmol) in DCM (10 mL) was added 2-furanylboronic acid
(36 mg, 0.32 mmol). The resulting solution was stirred at rt in dark
for 90 min. The solvent was evaporated. The residue was dissolved in
about 2 mL CHCl3 and precipitated by adding methanol. The process
was repeated three times to remove unreacted 2-furanylboronic
acid. The solid was then chromatographed on silica gel eluting
with toluene/petroleum ether (bp 60e90 ꢀC)/ethyl acetate (10:10:1)
to remove unknown impurities, and then toluene/ethyl acetate
(10:7) to yield the compound 2b as an orange solid (79 mg, 86%). 1H
(CDCl3, 400 MHz):
(s,1H),1.51 (s,18H),1.28 (s,18H).13C NMR: (CDCl3,100 MHz, all signals
represent 2C except where noted): 150.90, 150.13, 149.16, 149.12,
d
4.60 (t, J¼1.44 Hz, 2H), 4.48 (t, J¼1.54 Hz, 2H), 4.16
NMR (400 MHz, CDCl3):
1H), 1.48(s, 18H), 1.21(s, 18H). 13C NMR: (CDCl3, 100 MHz, all signals
represent 2C except noted): 151.09, 149.73, 149.14, 149.13, 148.66,
d
7.76 (s,1H), 7.32 (d, J¼2.48 Hz,1H), 6.53 (s,
d
148.64, 148.25 (3C), 148.20, 147.57, 147.53, 147.33, 147.29, 147.28 (1C),
146.91, 145.97, 145.78, 145.63, 145.61, 145.44, 144.99, 144.50, 143.97,
143.60, 143.39, 143.16, 142.99, 141.28, 138.66, 91.24 (1C), 85.11 (1C),
82.96, 82.09 (C-(CH3)3), 82.04 (C-(CH3)3), 80.78, 73.82, 72.22, 68.93
(5C), 67.89 (1C), 26.94 (6CH3), 26.82 (6CH3). FT-IR (microscope): 2979,
2926, 2852, 1483, 1385, 1364, 1319, 1268, 1243, 1192, 1127, 1105, 1092,
1038, 1023, 1005, 870, 816, 752 cmꢁ1. ESI-HRMS (m/z): C86H45BFeO10
(MþHþ) calculated: 1304.2465, found: 1304.2444.
d
148.34,148.30 (1C),148.16,148.10,147.79,147.58,147.33,147.27 (3C),
146.93, 145.63, 145.52, 145.27, 145.24, 145.11, 144.85, 144.44, 144.21,
143.78, 143.50, 143.30, 142.97, 141.22, 139.64, 124.82 (1C), 110.62
(1C), 91.39 (1C), 84.99 (1C), 82.26, 82.00 (C-(CH3)3), 81.98 (C-(CH3)3),
80.87, 26.73 (6CH3), 26.45 (6CH3). FT-IR (microscope): 2980, 2929,
2854,1578,1484,1364,1338,1303,1243,1231,1192,1165,1122,1096,
1077, 1042, 1024, 1004 cmꢁ1. HRMS (m/z): C80H43BNO11 (MþNHþ4 )
calculated: 1204.2936, found: 1204.2937.
3.2.7. Characterization data for compound 4. 1H NMR (CDCl3,
400 MHz):
NMR: (CDCl3,100 MHz, all signals represent 2C except where noted):
d 150.93, 150.22, 149.17, 149.12, 148.63, 148.27 (3C), 148.21, 147.57
d C
4.86 (s, 2H); 4.74 (s, 2H); 1.53 (s, 18H); 1.30 (s, 18H). 13
3.2.4. Compound 2c. To
a solution of compound 1 (95 mg,
0.085 mmol) in DCM (20 mL) was added 2-benzofuranylboronic
acid (28 mg, 0.17 mmol). The resulting solution was stirred at rt
in dark for 90 min. The solvent was evaporated. The residue was
dissolved in about 2 mL CHCl3 and precipitated by adding metha-
nol. The process was repeated three times to remove unreacted 2-
benzofuranylboronic acid. The solid was then chromatographed on
silica gel eluting with toluene/petroleum ether (bp 60e90 ꢀC)/ethyl
acetate (10:10:1) to remove unknown impurities, and then toluene/
ethyl acetate (10:7) to yield the compound 2c as an orange solid
(4C),147.35,147.31,147.29 (1C),146.93,146.04,145.76,145.66,145.64,
145.47, 144.99, 144.50, 144.00, 143.61, 143.41, 143.18, 143.00, 141.33,
138.66, 91.34, 85.15, 82.98, 82.05 (C-(CH3)3), 82.01 (C-(CH3)3), 80.81,
74.67, 73.67, 26.98 (6CH3), 26.86 (6CH3). Molecular ion signal was not
observed in the Mass spectrum because of unstability.
3.2.8. Compound 5. To
a solution of compound 1 (160 mg,
0.14 mmol) in DCM (20 mL) was added bis(pinacolato)diboron
(75 mg, 0.25 mmol). The resulting solution was stirred at rt in dark
(101 mg, 95%). 1H NMR (400 MHz, CDCl3):
d
7.73 (d, J¼7.72 Hz, 1H),

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Z. Dai et al. / Tetrahedron 68 (2012) 5193e5196
for 30 min. The solvent was evaporated. The residue was dissolved
in about 3 mL CHCl3 and precipitated by adding methanol. The
process was repeated three times to remove unreacted bis(pina-
colato)diboron. The solid was then chromatographed on silica gel
eluting with DCM/petroleum ether (bp 60e90 ꢀC) (1:3) to yield the
compound 7 as an orange solid (84 mg, 46%). 1H NMR (CDCl3,
Supplementary data
Selected spectroscopic data for new compounds and crystal-
lographic data for 2a including CIF file. Supplementary data re-
lated to this article can be found online at doi:10.1016/
j.tet.2012.03.092.
400 MHz):
d
1.45 (s, 18H), 1.38 (s, 18H), 1.32 (s, 12H). 13C NMR:
150.67,
(CDCl3, 100 MHz, all signals represent 2C except noted):
d
149.94, 149.12, 149.09, 148.63, 148.31, 148.28 (1C), 148.11, 148.09,
147.56, 147.31, 147.28, 147.23 (1C), 146.89, 145.68, 145.47, 145.43,
145.31, 145.23, 144.87, 144.40, 144.22, 143.74, 143.45, 143.13, 143.06,
141.44, 139.26, 91.45 (1C), 85.10 (1C), 83.88, 82.36 (C-(CH3)3), 81.86
(C-(CH3)3), 81.80, 80.85, 26.86 (6CH3), 26.75 (6CH3), 25.00. FT-IR
(microscope): 2980, 2929, 2869, 2248, 1465, 1388, 1364, 1292,
1261, 1193, 1169, 1130, 1105, 1043, 1023, 1003, 926, 908, 872, 853,
752, 733 cmꢁ1. ESI-HRMS (m/z): C82H52B2NO2 (MþNH4þ) calculated:
1264.3676, found: 1264.3693.
References and notes
1. For recent books: (a) Fullerenes: From Synthesis to Optoelectronic Properties;
Guldi, D. M., Martin, N., Eds.; Kluwer Academic: Dordrecht, The Netherlands,
2002; (b) Hirsch, A. The Chemistry of Fullerenes; Wiley-VCH: Weinheim, Ger-
many, 2005; (c) Fullerenes. Principles and Applications; Langa, F., Nierengarten,
J.-F., Eds.; RSC: Cambridge, United Kingdom, 2007.
2. Semenov, K. N.; Charykov, N. A.; Keskinov, V. A.; Piartman, A. K.; Blokhin, A. A.;
Kopyrin, A. A. J. Chem. Eng. Data 2010, 55, 13.
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Mater. Chem. 2002, Vol. 12; (c) Bosi, S.; Da Ros, T.; Spalluto, G.; Prato, M. Eur. J.
Med. Chem. 2003, 38, 913; (d) Ma, H. L.; Liang, X.-J. Sci. China: Chem. 2010, 53,
2233.
3.2.9. Compound 7a. To
a solution of compound 6 (60 mg,
4. (a) Brabec, C. J.; Gowrisanker, S.; Halls, J. J. M.; Laird, D.; Jia, S. J.; Williams, S. P.
Adv. Mater. 2010, 22, 3839.
5. (a) Bingel, C. Chem. Ber. 1993, 126, 1957; (b) Diederich, F.; Isaacs, L.; Philp, D.
Chem. Soc. Rev. 1994, 23, 243.
6. (a) Maggini, M.; Scorrano, G.; Prato, M. J. Am. Chem. Soc. 1993, 115, 9798; (b)
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0.061 mmol) in CHCl3 (12 mL) was added phenylboronic acid
(32 mg, 0.26 mmol). The resulting solution was stirred at rt in dark
for 20 min. The solution was chromatographed on silica gel eluting
with toluene to yield the compound 7a as an orange solid (66 mg,
93%). 1H NMR (CDCl3, 600 MHz)
d
1.26 (s, 18H), 7.52 (t, J¼7.50 Hz,
7. Miller, G. P. C. R. Chim. 2006, 9, 952.
4H), 7.60 (t, J¼7.20 Hz, 2H), 8.15 (d, J¼7.20 Hz, 4H). 13C NMR: (CDCl3,
8. Heymann, D. Fullerenes, Nanotubes, Carbon Nanostruct. 2004, 12, 715.
9. Delgado, J. L.; Martin, N.; de la Cruzc, P.; Langa, F. Chem. Soc. Rev. 2011, 40, 5232.
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150 MHz, all signals represent 2C except noted)
d 149.86, 149.39,
149.00, 148.82, 148.63 (1C), 148.58, 148.43, 148.33, 148.09, 148.01,
147.59, 147.43 (1C), 146.77, 146.34, 146.32, 145.35, 145.18, 145.10
(4C), 144.98, 144.81, 144.78, 144.28, 144.22, 144.19, 139.09, 137.83,
136.03 (4C), 132.64 (2C), 128.36 (4C), 88.16, 87.51, 82.62, 81.05,
75.74 (1C), 64.88 (1C), 27.14 (6CH3). FT-IR (microscope): 3080, 3056,
3023, 2980, 2926, 2852, 1604, 1499, 1439, 1396, 1360, 1260, 1191,
1095, 1029, 1011, 759, 697, 640 cmꢁ1. ESI-HRMS: C80H29B2O9
(MþHþ) calculated: 1155.2015, found: 1155.2021.
11. Chuang, S.-C.; Rajeshkumar, V.; Cheng, C.-A.; Deng, J.-C.; Wang, G.-W. J. Org.
Chem. 2011, 76, 1599.
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3.2.10. Compound 7b. To
a solution of compound 6 (60 mg,
0.061 mmol) in CHCl3 (12 mL) was added 4-chlorophenylboronic acid
(38 mg, 0.24 mmol). The resulting solution was stirred at rt in dark for
5 min. The solution was chromatographed on silica gel eluting with
toluene to yield the compound 7b as an orange solid (68 mg, 91%). 1H
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NMR (CDCl3, 400 MHz)
d
1.24 (s,18H), 7.50 (d, J¼8.40 Hz, 4H), 8.07 (d,
J¼8.40 Hz, 4H). 13C NMR: (CDCl3, 100 MHz, all signals represent 2C
except noted)
d 149.46, 148.97, 148.56, 148.42, 148.23 (1C), 148.16,
147.99,147.77,147.66,147.57,147.15,147.00 (1C),146.11,145.83,145.63,
144.94, 144.77, 144.70, 144.61, 144.47, 144.36, 144.33, 143.81, 143.74,
143.68, 138.67, 138.62, 137.29, 136.93 (4C), 128.37 (4C), 87.77, 87.11,
82.24, 80.57, 75.18 (1C), 64.50 (1C), 26.70 (6CH3). FT-IR (microscope):
3041, 2979, 2930, 2869, 1597, 1395, 1360, 1256, 1190, 1095, 1047, 1017,
961, 921, 825, 760, 724, 642 cmꢁ1. ESI-HRMS: C80H30B2Cl2NO9
(MþNHþ4 ) calculated: 1240.1502, found: 1240.1490.
20. For
a recent example about decomposition of ferrocene, see: Amara, D.;
Grinblat, J.; Margel, S. J. Mater. Chem. 2012, 22, 2188.
21. Zhang, G.; Liu, Y.; Liang, D. H.; Gan, L. B.; Li, Y. L. Angew. Chem., Int. Ed. 2010, 49,
5293.
Acknowledgements
22. (a) Wang, G.-W.; Shu, L.-H.; Wu, S.-H.; Wu, H.-M.; Lao, X.-F. J. Chem. Soc., Chem.
Commun. 1995, 1071; (b) Li, F.-B.; Liu, T.-X.; You, X.; Wang, G.-W. Org. Lett. 2010,
12, 3258.
This work is supported by NSFC (20972003, 21132007) and the
Major State Basic Research Development Program (2011CB808401).