Benzylic-acetoxylation of alkylbenzenes with PhI(OAc)2 in the presence of catalytic amounts of TsNH2 and I2

Article abstract of DOI:10.1016/j.tetlet.2011.06.036

Treatment of alkylbenzenes with (diacetoxyiodo)benzene in the presence of catalytic amounts of p-toluenesulfonamide or p-nitrobenzenesulfonamide, and molecular iodine in 1,2-dichloroethane at 60 °C gave the corresponding (α-acetoxy)alkylbenzenes in good to moderate yields. The present reaction is a simple method for the introduction of an acetoxy group to the benzylic position of alkylbenzenes.

Full text of DOI:10.1016/j.tetlet.2011.06.036

Tetrahedron Letters 52 (2011) 4303–4307
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Tetrahedron Letters
journal homepage: www.elsevier.com/locate/tetlet
Benzylic-acetoxylation of alkylbenzenes with PhI(OAc)2 in the presence
of catalytic amounts of TsNH2 and I2
⇑
Haruka Baba, Katsuhiko Moriyama, Hideo Togo
Graduate School of Science, Chiba University, Yayoi-cho 1-33, Inage-ku, Chiba 263-8522, Japan
a r t i c l e i n f o
a b s t r a c t
Article history:
Treatment of alkylbenzenes with (diacetoxyiodo)benzene in the presence of catalytic amounts of
Received 16 May 2011
Revised 7 June 2011
Accepted 8 June 2011
Available online 16 June 2011
p-toluenesulfonamide or p-nitrobenzenesulfonamide, and molecular iodine in 1,2-dichloroethane at
60 °C gave the corresponding (a-acetoxy)alkylbenzenes in good to moderate yields. The present reaction
is a simple method for the introduction of an acetoxy group to the benzylic position of alkylbenzenes.
Ó 2011 Elsevier Ltd. All rights reserved.
Keywords:
(Diacetoxyiodo)benzene
(Dibenzoyloxyiodo)benzene
Alkylbenzene
p-Toluenesulfonamide
p-Nitrobenzenesulfonamide
(a
-Acetoxy)alkylbenzene
Molecular iodine
(Diacetoxyiodo)benzene (DIB) is one of the most useful hyper-
valent iodine reagents for organic synthesis because it can serve
as an alternative to toxic heavy-metal reagents.1 The advantages
of DIB are as follows: it is a non-metal oxidant and it can be used
for not only polar reactions, but also radical reactions to generate
oxygen-centered radicals, nitrogen-centered radicals, and carbon-
centered radicals.2 For the radical reactions, a DIB-molecular iodine
(I2) system is used and the initial formation of acetyl hypoiodite
(CH3CO2I) from the reaction of DIB and I2 is the key step.3 Synthetic
studies of alkoxyl radicals derived from substrates, such as steroi-
dal alcohols and sugars, with DIB and I2 have been well carried out
by Suarez et al.2 We have also examined the synthetic utility of
nitrogen-centered radicals for the construction of tetrahydroquin-
olines, benzosultams, and saccharins from sulfonamides with DIB
and I2 under irradiation with a tungsten lamp,4 and oxygen-
centered radicals for the construction of chromans from 3-aryl-
propanols with DIB and I2 under irradiation with a tungsten lamp.5
The formation of tetrahydroquinolines, benzosultams, and chro-
mans proceeds through the intramolecular cyclization of the
formed sulfonamidyl radicals and alkoxyl radicals onto their aro-
ethylbenzene with DIB, I2, and p-toluenesulfonamide in 1,2-dichlo-
roethane gave a mixture of -(p-toluenesulfonylamido)ethylben-
zene and -(acetoxy)ethylbenzene in 5% and 4% yields,
respectively.6 We have also reported the preparation of
-(p-tolu-
enesulfonylamido)alkylbenzenes from alkylbenzenes with p-tolu-
enesulfonamide and 1,3-diiodo-5,5-dimethylhydantoin (DIH),
which works as synthon of a DIB and I2 system.7 Here, as part of
our synthetic study of DIB for organic synthesis,4,5 we would like
to report the benzylic-acetoxylation of alkylbenzenes with DIB in
the presence of catalytic amounts of p-toluenesulfonamide and
I2. To the best of our knowledge, the following methods for the
a
a
a
practical preparation of
a-(acetoxy)alkylbenzenes from alkylben-
zenes are known, such as K2S2O8 with transition metal salts in
AcOH at 115 °C,8a K2S2O8/LiBr (cat.)/AcONa in AcOH at 115 °C,8b
CAN (cerium ammonium nitrate, cat.)/KBrO3 in AcOH at
90–110 °C,8c NHPI (N-hydroxyphthalimide, cat.)/Co(OAc)2 (cat.)
/HNO3 (cat.) under air in AcOH at 80 °C,8d DDQ (2,3-dichloro-5,6-
dicyano-1,4-benzoquinone) in AcOH under ultrasonic irradiation,8e
NaIO4/LiBr(cat.) in AcOH at 90–110 °C,8f and related reactions.8g,h
The Pd(OAc)2-catalyzed
a-acetoxylation of alkylbenzenes with
matic rings. Recently, the
with DIB, I2, and p-toluenesulfonamide at 50 °C without solvent
a
-sulfonylamidation of alkylbenzenes
DIB in AcOH at 100 °C, and the Pd(OAc)2/CuI-catalyzed a-acetoxy-
lation of alkylbenzenes with oxygen in AcOH were also reported.9
However, there are several drawbacks such as toxicity and/or the
high cost of some transition metals.
was reported to provide a-(p-toluenesulfonylamido)alkylbenzenes
in moderate to good yields.6 In those reactions, the reaction of
The present reaction was carried out as follows: ethylbenzene 1a,
DIB, I2, and p-toluenesulfonamide were added to 1,2-dichloroethane
under an argon atmosphere. The mixture was warmed at 60 °C for
2 h. After the reaction, the mixture was poured into satd aq sodium
⇑
Corresponding author. Tel./fax: +81 43 290 2792.
E-mail address: togo@faculty.chiba-u.jp (H. Togo).
0040-4039/$ - see front matter Ó 2011 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tetlet.2011.06.036

4304
H. Baba et al. / Tetrahedron Letters 52 (2011) 4303–4307
Table 2
sulfite solution and extracted with diethyl ether. After removal of
the ether solvent, the residue was subjected to preparative TLC on
a-Acetoxylation of alkylbenzenes with a DIBÁI2ÁArSO2NH2 system
silica gel to give
in Table 1 (entry 5).10 In the absence of either I2 or p-toluenesulfon-
amide under the same conditions, -(acetoxy)ethylbenzene was not
a-(acetoxy)ethylbenzene 2a in 63% yield as shown
a
formed at all (entries 8 and 11). This suggests that I2 and p-toluene-
sulfonamide, respectively, work as catalysts in the present reaction.
Instead of using DIB as the oxidant, [bis(trifluoroacetoxy)iodo]ben-
zene was employed. However, [bis(trifluoroacetoxy)iodo]benzene
did not work at all, whereas p-chloro[(diacetoxy)iodo]benzene
and p-methyl[(diacetoxy)iodo]benzene worked to generate
a-
(acetoxy)ethylbenzene 2a in moderate yields (entries 13–15).
OxoneÒ tBuOCl, and DIH (1,3-diiodo-5,5-dimethylhydantoin) also
,
did not work at all as an oxidant, respectively (entries 16ꢀ18). When
acetonitrile and carbon tetrachloride instead of 1,2-dichloroethane
as solvent were used, the yield of
a-(acetoxy)ethylbenzene was
decreased to ꢀ30% yield (entries 19 and 20). The same treatment
of ethylbenzene with DIB, I2, and p-toluenesulfonamide in 1,2-
dichloroethane under irradiation conditions with a tungsten lamp
provided
with warming conditions at 60 °C (entries 5 and 21). When [bis(ben-
zoyloxy)iodo]benzene was used instead of DIB, -(benzoyloxy)eth-
ylbenzene 3a was obtained in good yield (entry 22). These results
indicate that the acetoxy group of -(acetoxy)ethylbenzene 2a
a-(acetoxy)ethylbenzene in almost the same yield as that
Entry
R1
R2
Yielda (%)
2
3
a
A1
A2
A1
a
1
2
H
Br
CH3
CH3
63
66
73
72
67
61
comes from the acetoxy group of DIB. Based on these results, other
3
4
5
C(CH3)3
C2H5
CO2CH3
CH3
CH3
CH3
66
68
58
38 (44)b
48
29 (51)b
59
43 (27)b
37
Table 1
a
-Acetoxylation of ethylbenzene with a DIBÁI2ÁTsNH2 system
6
7
8
9
10
11
12
13
NO2
CON(CH3)2
CH3
CH3
27
35
28
54
60
31
42
57
81
29
35
39
57
45
30
48
61
52 (25)c
42
H
H
H
H
H
Ph
CH2CH3
(CH2)2CH3
(CH2)2OAc
(CH2)2Br
(CH2)6CH3
(CH2)3CH3
48
27
36
52
Entry
DIB (equiv)
I2 (equiv)
TsNH2 (equiv)
AcOH (mL)
Yield (%)
64
1a
2b
3b
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19i
20j
21k
22
2.0
2.0
1.5
2.0
2.5
3.0
2.5
2.5
2.5
2.5
2.5
2.5
2.5c
2.5d
2.5e
2.0f
2.0g
2.0h
2.5
2.5
2.5
2.5l
0.2
0.2
0.2
0.2
0.2
0.2
0.1
0
0.2
0.2
0.2
0.5
0.2
0.2
0.2
0.2
0.2
0.2
0.2
0.2
0.2
0.2
0.2
0.2
0.2
0.2
0.2
0.2
0.2
0.2
0.3
0.1
0
0.5
0.2
0.2
0.2
0.2
0.2
0.2
0.2
0.2
0.2
0.2
1
1
1
0
0
0
0
0
0
0
0
0
1
0
0
1
1
1
0
0
0
0
25
50
42
57
63
59
47
0
61
43
0
24
0
56
50
0
0
3
33
29
61
67m
14
61 (9)d
48 (13)d
51 (11)e
15
16
61
37
51
55 (1:0.7)f
63 (1:0.7)f
58 (1:0.8)g
a
Isolated yield.
Yield of compound I.
b
a
b
c
d
e
f
The reaction time was 10 min.
The reaction time was 1 h.
c
Yield of compound II.
Instead of DIB, [bis(trifluoroacetoxy)iodo]benzene was used.
Instead of DIB, p-chloro(diacetoxyiodo)benzene was used.
Instead of DIB, p-methyl(diacetoxyiodo)benzene was used.
Instead of DIB, oxone was used.
g
h
i
Instead of DIB, tBuOCl was used.
Instead of DIB, DIH was used.
CH3CN was used as solvent.
CCl4 was used as solvent.
j
d
Yield of compound III.
k
l
Irradiated with a tungsten lamp.
Instead of DIB, [bis(benzoyloxy)iodo]benzene was used.
m
Yield of 3a.

H. Baba et al. / Tetrahedron Letters 52 (2011) 4303–4307
4305
DIB in the presence of I2 and p-toluenesulfonamide generated 4-
-acetoxy)ethyl-N,N-dimethylbenzamide in 52% yield together
with 4-( -acetoxy)ethyl-N-methylbenzamide in 25% yield, which
Table 2 (continued)
(a
e
a
Yield of compound IV.
was an N-demethylated compound (entry 7). The same treatment
of fluorene and diphenylmethane with DIB, I2, and p-toluenesulfon-
amide provided the corresponding a-acetoxy compounds in good to
moderate yields (entries 14 and 15). When 1,2,3,4-tetrahydronaph-
thalene was used, a mixture of cis- and trans-1,4-diacetoxy-1,2,3,4-
tetrahydronaphthalenes was obtained in 55% yield. Moreover, when
p-nitrobenzenesulfonamide (A2), which may have stronger N–H
bond energy than that of p-toluenesulfonamide due to the presence
of an electron-withdrawing group, was used instead of p-toluene-
f
Yield of compound V.
sulfonamide (A1), the yield of
a-acetoxylated compounds was
slightly increased (from column A1 to column A2). The same treat-
ment of alkylbenzenes with [bis(benzoyloxy)iodo]benzene instead
of DIB, generated the corresponding
However, there is not so much difference in yield between DIB
a-benzoyloxy compounds 3.
g
Yield of compound VI.
and [bis(benzoyloxy)iodo]benzene.
A plausible reaction mechanism is shown in Scheme 1. The ini-
tial formation of N-iodo-p-toluenesulfonamide from the reaction of
p-toluenesulfonamide with DIB in the presence of I2 occurs, and
this is followed by homolytic N–I bond cleavage to generate a sul-
fonamidyl radical.
The sulfonamidyl radical abstracts a benzylic hydrogen atom
from alkylbenzene to provide a benzyl radical that may be oxidized
to benzylic cation with DIB. Once a benzylic cation is formed, it
alkylbenzenes, such as 4-bromo-1-ethylbenzene, 4-t-butyl-1-ethyl-
benzene, methyl 4-ethylbenzoate, 4-ethyl-N,N-dimethylbenza-
mide, n-propylbenzene, n-butylbenzene, n-octylbenzene, and
4-pentyl-1-biphenyl were treated with DIB, I2, and p-toluenesulfon-
smoothly reacts with acetic acid to give
a-(acetoxy)alkylbenzene.
Practically, the addition of galvinoxyl free radical completely re-
tarded the present reaction and ethylbenzene was obtained with
high recovery under the same conditions.
In conclusion, treatment of alkylbenzenes with DIB in the pres-
ence of catalytic amounts of I2 and p-toluenesulfonamide at 60 °C
amide at 60 °C to provide the corresponding
zenes in good to moderate yields as shown in Table 2 (entries 2, 3,
5, 7–9, 12, and 13). When 1,4-diethylbenzene was used 1- -(acet-
oxyethyl)-4-ethylbenzene was obtained in 38% yield together with
1,4-di( -acetoxy)ethylbenzene in 44% yield (entry 4). The yields of
-acetoxy compounds were low when p-nitroethylbenzene was
a-(acetoxy)alkylben-
a
gave the corresponding (
a-acetoxy)alkylbenzenes in good to mod-
a
erate yields. The present reaction is a simple method for the
a-
a
acetoxylation at the benzylic position of alkylbenzenes. Further
synthetic studies using the present reaction are under way in this
laboratory.
used (entry 6). Treatment of 4-ethyl-N,N-dimethylbenzamide with
Acknowledgments
Financial support in the form of a Grant-in-Aid for Scientific
Research (No. 20550033) from the Ministry of Education, Culture,
Sports, Science, and Technology in Japan, Iodine Research Project
in Chiba University, and Futaba Electronics Memorial Foundation
is gratefully acknowledged.
References and notes
1. Reviews: (a) Moriarty, R. M.; Vaid, R. K. Synthesis 1990, 431; (b) Stang, P. J.
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Synlett 1994, 221; (d) Kitamura, T. Yuki Gosei Kagaku Kyokaishi 1995, 53, 893;
(e) Stang, P. J.; Zhdankin, V. V. Chem. Rev. 1996, 96, 1123; (f) Umemoto, T. Chem.
Rev. 1996, 96, 1757; (g) Kita, Y.; Takada, T.; Tohma, H. Pure Appl. Chem. 1996, 68,
627; (h) Togo, H.; Hoshina, Y.; Nogami, G.; Yokoyama, M. Yuki Gosei Kagaku
Kyokaishi 1997, 55, 90; (i) Varvoglis, A. Tetrahedron 1997, 53, 1179; (j)
Zhdankin, V. V. Rev. Heteroatom Chem. 1997, 17, 133; (k) Muraki, T.; Togo, H.;
Yokoyama, M. Rev. Heteroatom Chem. 1997, 17, 213; (l) Kitamura, T.; Fujiwara,
Y. Org. Prep. Proced. Int. 1997, 29, 409; (m) Varvoglis, A.; Spyroudis, S. Synlett
1998, 221; (n) Zhdankin, V. V.; Stang, P. J. Tetrahedron 1998, 54, 10927; (o)
Moriarty, R. M.; Prakash, O. Adv. Heterocycl. Chem. 1998, 69, 1; (p) Togo, H.;
Katohgi, M. Synlett 2001, 565; (q) Zhdankin, V. V.; Stang, P. J. Chem. Rev. 2002,
102, 2523; (r) Richardson, R. D.; Wirth, T. Angew. Chem., Int. Ed. 2006, 45, 4402;
(s) Ladziata, U.; Zhdankin, V. Synlett 2007, 527; (t) Zhdankin, V. V.; Stang, P. J.
Chem. Rev. 2008, 108, 5299; (u) Merritt, E. A.; Olofsson, B. Synthesis 2011, 517.
2. Review: (a) Togo, H.; Katohgi, M. Synlett 2001, 565; Papers: (b) de Armas, P.;
Carrau, R.; Concepcion, J. I.; Francisco, C. G.; Hernandez, R.; Suarez, E.
Tetrahedron Lett. 1985, 26, 2493; (c) Freire, R.; Marrero, J. J.; Rodriguez, M. S.;
Suarez, E. Tetrahedron Lett. 1986, 27, 383; (d) Freire, R.; Hernandez, R.;
Rodriguez, M. S.; Suarez, E.; Perales, P. Tetrahedron Lett. 1987, 28, 981; (e)
Francisco, C. G.; Freire, R.; Rodriguez, M. S.; Suarez, E. Tetrahedron Lett. 1987, 28,
3397; (f) Carrau, R.; Hernandez, R.; Suarez, E.; Betancor, C. J. Chem. Soc., Perkin
Scheme 1. Plausible reaction mechanism.

4306
H. Baba et al. / Tetrahedron Letters 52 (2011) 4303–4307
Trans. 1 1987, 937; (g) Hernandez, R.; Medina, M. C.; Salazar, J. A.; Suarez, E.
Tetrahedron Lett. 1987, 28, 2533; (h) de Armas, P.; Francisco, C. G.; Hernandez,
R.; Salazar, J. A.; Suarez, E. J. Chem. Soc., Perkin Trans. 1988, 3255; (i)
1-(
a
-Benzoyloxy)ethyl-4-ethylbenzene (C17H18O2): IR (Neat): 1113, 1270,
1715 cmÀ1
;
1H NMR (CDCl3, TMS) d = 1.24 (t, J = 7.7 Hz, 3H), 1.66 (d,
1
J = 6.6 Hz, 3H), 2.64 (q, J = 7.7 Hz, 2H), 6.11 (q, J = 6.6 Hz, 1H), 7.20 (d,
J = 8.1 Hz, 2H), 7.37 (d, J = 8.1 Hz, 2H), 7.42 (t, J = 7.5 Hz, 2H), 7.57 (t,
J = 7.5 Hz, 1H), 8.07 (d, J = 7.5 Hz, 2H); 13C NMR(CDCl3, TMS) d = 15.4, 22.2,
28.5, 72.8, 126.1, 127.9, 128.2, 129.6, 130.5, 132.8, 138.9, 143.9, 165.7;
Hernandez, R.; Marrero, J. J.; Suarez, E. Tetrahedron Lett. 1988, 29, 5979; (j)
Hernandez, R.; Marrero, J. J.; Melian, D.; Suarez, E.; Melian, D. Tetrahedron Lett.
1988, 29, 6661; (k) Hernandez, R.; Marrero, J. J.; Suarez, E. Tetrahedron Lett.
1989, 30, 5501; (l) Dorta, R. L.; Francisco, C. G.; Suarez, E. Chem. Commun. 1989,
1168; (m) Arencibia, M. T.; Freire, R.; Perales, A.; Rodriguez, M. S.; Suarez, E. J.
Chem. Soc., Perkin Trans. 1 1991, 3349; (n) Boto, A.; Betancor, C.; Prange, T.;
Suarez, E. Tetrahedron Lett. 1992, 33, 6687; (o) de Armas, P.; Francisco, C. G.;
Suarez, E. Angew. Chem., Int. Ed. Engl 1992, 31, 772.
HRMS (ESI) calcd for
277.1196.
C
17H18O2Na [M+Na]+: m/z 277.1199, found m/z
1,4-Bis(a ;
-acetoxyethyl)benzene (C14H18O4): IR (Neat): 1065, 1240, 1739 cmÀ1
1H NMR (CDCl3, TMS) d = 1.52 (d, J = 6.3 Hz, 6H), 2.07 (s, 6H), 5.87 (q, J = 6.3 Hz,
2H), 7.33(s, 4 H); 13C NMR (CDCl3, TMS) d = 21.3, 22.1, 72.0, 126.3, 141.3, 170.3;
HRMS (ESI) calcd for C14H18O4Na [M+Na]+: m/z 273.1097, found m/z 273.1093.
3. (a) Ogata, Y.; Aoki, K. J. Am. Chem. Soc. 1968, 90, 6187; (b) Merkushev, E. B.;
Simakhina, N. D.; Koveshnikova, G. M. Synthesis 1980, 486.
1,4-Bis(
a
-benzoyloxyethyl)benzene (C24H22O4): IR (Neat): 1065, 1268,
;
4. (a) Togo, H.; Katohgi, M.; Yokoyama, M. Synlett 1998, 131; (b) Togo, H.;
Hoshina, Y.; Muraki, T.; Nakayama, H.; Yokoyama, M. J. Org. Chem. 1998, 63,
5193; (c) Katohgi, M.; Togo, H.; Yamaguchi, K.; Yokoyama, M. Tetrahedron 1999,
55, 14885; (d) Togo, H.; Nabana, T.; Yokoyama, M. J. Org. Chem. 2000, 65, 8391;
(e) Togo, H.; Harada, Y.; Yokoyama, M. J. Org. Chem. 2000, 65, 926.
5. (a) Muraki, T.; Togo, H.; Yokoyama, M. Tetrahedron Lett. 1996, 37, 2441; (b)
Togo, H.; Muraki, T.; Hoshina, Y.; Yamaguchi, K.; Yokoyama, M. J. Chem. Soc.,
Perkin Trans. 1 1997, 787.
1713 cmÀ1
1H NMR (CDCl3, TMS) d = 1.66 (d, J = 6.6 Hz, 6H), 6.13 (q,
J = 6.6 Hz, 2H), 7.43 (t, J = 7.3 Hz, 4H), 7.45 (s, 4H), 7.55 (t, J = 7.3 Hz, 2H),
8.07 (d, J = 7.3 Hz, 4H); 13C NMR(CDCl3, TMS) d = 22.3, 72.6, 126.3, 128.3, 129.6,
130.4, 132.9, 141.4, 165.8; HRMS (ESI) calcd for C24H22O4Na [M+Na]+:m/z
397.1410, found m/z 397.1404.
Methyl 4-(
a
-acetoxy)ethylbenzoate (C12H14O4): IR (Neat): 1067, 1236,
1719 cmÀ1
;
1H NMR (CDCl3, TMS) d = 1.53 (d, J = 6.6 Hz, 3H), 2.09 (s, 3H),
3.91 (s, 3H), 5.90 (q, J = 6.6 Hz, 1H), 7.41 (d, J = 8.2 Hz, 2H), 8.02 (d, J = 8.2 Hz,
2H); 13C NMR(CDCl3, TMS) d = 21.1, 22.1, 52.0, 71.7, 125.8, 129.5, 129.8, 146.7,
166.6, 170.1; HRMS (ESI) calcd for C12H14O4Na [M+Na]+: m/z 245.0784, found
m/z 245.0781.
6. Fan, R.; Li, W.; Pu, D.; Zhang, L. Org. Lett. 2009, 11, 1425.
7. Baba, H.; Togo, H. Tetrahedron Lett. 2010, 51, 2063.
8. (a) Belli, A.; Giordano, C.; Citterio, A. Synthesis 1980, 447; (b) Citterio, A.; Santi,
R.; Pagani, A. J. Org. Chem. 1987, 52, 4925; (c) Ganin, E.; Amer, I. J. Mol. Catal. A:
Chem. 1997, 116, 323; (d) Minisci, F.; Recupero, F.; Gambarotti, C.; Punta, C.;
Paganelli, R. Tetrahedron Lett. 2003, 44, 6919; (e) Kumar, V.; Sharma, A.;
Sharma, M.; Sharma, U. K.; Sinha, A. K. Tetrahedron 2007, 63, 9718; (f) Shaikh, T.
M.; Sudalai, A. Tetrahedron Lett. 2005, 46, 5587; (g) Lee, J. M.; Park, E. J.; Cho, S.
H.; Chang, S. J. Am. Chem. Soc. 2008, 130, 7824; (h)Other methods with metals:
Comprehensive Organic Transformation; Larock, R. C., Ed.; VCH Publishers, 1989;
p 823.
Methyl 4-(
a
;
-benzoyloxy)ethylbenzoate (C17H16O4): IR (Neat): 1110, 1263,
1713 cmÀ1
1H NMR (CDCl3, TMS) d = 1.68 (d, J = 6.5 Hz, 3H), 3.91 (s, 3H), 6.15
(q, J = 6.5 Hz, 1H), 7.45 (t, J = 7.5 Hz, 2H), 7.50 (d, J = 8.4 Hz, 2H), 7.57 (t,
J = 7.5 Hz, 1H), 8.04 (d, J = 8.4 Hz, 2H), 8.08 (d, J = 7.5 Hz, 2H); 13C NMR(CDCl3,
TMS) d = 22.3, 52.0, 72.3, 125.8, 128.3, 129.6, 129.9, 130.0, 130.1, 133.0, 146.8,
165.6, 166.6; HRMS (ESI) calcd for C17H16O4Na [M+Na]+: m/z 307.0941, found
m/z 307.0934.
4-(
a-Acetoxy)ethyl-1-nitrobenzene (C10H11O4N): IR (Neat): 1069, 1238, 1348,
9. (a) Dick, A. R.; Hull, K. L.; Sanford, M. S. J. Am. Chem. Soc. 2004, 126, 2300; (b)
Jiang, H.; Chen, H.; Wang, A.; Lin, X. Chem. Commun. 2010, 46, 7259; (c) Zhang,
S.; Luo, F.; Wang, W.; Jia, X.; Hu, M.; Cheng, J. Tetrahedron Lett. 2010, 51, 3317.
1524, 1739 cmÀ1 1H NMR (CDCl3, TMS) d = 1.55 (d, J = 6.7 Hz, 3H), 2.11 (s, 3H),
;
5.92 (q, J = 6.7 Hz, 1H), 7.51 (d, J = 8.7 Hz, 2H), 8.22 (d, J = 8.7 Hz, 2H); 13C NMR
(CDCl3, TMS) d = 21.1, 22.2, 71.2, 123.8, 126.7, 147.4, 149.0, 170.0; HRMS(APPI)
calcd for C10H10O4N [MÀH]+: m/z 208.0604, found m/z 208.0604.
10. Typical procedure for preparation of a-(acetoxy)ethylbenzene with ethylbenzene,
DIB, I2, and p-toluenesulfonamide: (Diacetoxyiodo)benzene (5 mmol, 1.61 g), I2
(0.4 mmol, 102 mg), p-toluenesulfonamide (0.4 mmol, 68.4 mg), and
ethylbenzene (2 mmol, 184 mg) were added to dichloroethane (3 mL). The
mixture was warmed at 60 °C for 2 h under an argon atmosphere. Then, the
mixture was poured into saturated aqueous sodium sulfite solution and
extracted with diethyl ether (3 Â 20 mL). The organic layer was dried over
Na2SO4. After filtration and removal of the solvent under reduced pressure, the
residue was subjected to preparative TLC on silica gel using a mixture of
4-(
a-Benzoyloxy)ethyl-1-nitrobenzene (C15H13O4N):IR (Neat): 1069, 1270,
1348, 1522, 1719 cmÀ1
;
1H NMR (CDCl3, TMS) d = 1.70 (d, J = 6.6 Hz, 3H),
6.18 (q, J = 6.6 Hz, 1H), 7.48 (t, J = 7.0 Hz, 2H), 7.56 (t, J = 7.0 Hz, 1H), 7.61 (d,
J = 8.8 Hz, 2H), 8.08 (d, J = 7.0 Hz, 2H), 8.23 (d, J = 8.8 Hz, 2H); 13C NMR (CDCl3,
TMS) d = 22.4, 71.8, 123.9, 126.7, 128.5, 129.7, 129.8, 133.3, 147.5, 149.1, 165.6;
HRMS(APPI) calcd for C15H12O4N [MÀH]+: m/z 270.0761, found m/z 270.0754.
4-(
a-Acetoxy)ethyl-N,N-dimethylbenzamide (C13H17O3N): IR (Neat): 1065,
1241, 1633, 1733, 3354, 3460 cmÀ1
;
1H NMR (CDCl3, TMS) d = 1.53 (d,
hexane and ethyl acetate (5:1) as an eluent to give
a
-(acetoxy)ethylbenzene in
J = 6.6 Hz, 3H), 2.09 (s, 3H), 3.05 (br, 6H), 5.89 (q, J = 6.6 Hz, 1H), 7.39 (q,
J = 8.5 Hz, 4H); 13C NMR(CDCl3, TMS) d = 21.3, 22.2, 35.3, 39.6, 71.8, 126.0,
127.3, 135.8, 143.1, 170.2, 171.2; HRMS (ESI) calcd for C13H17O3NNa [M+Na]+:
m/z 258.1101, found m/z 258.1095.
63% yield.
(
a
-Acetoxy)ethylbenzene (C10H12O2): IR (Neat): 1065, 1241, 1743 cmÀ1 1H NMR
;
(CDCl3, TMS) d = 1.53 (d, J = 6.6 Hz, 3H), 2.07 (s, 3H), 5.88 (q, J = 6.6 Hz, 1H),
7.26–7.36 (m, 5H); 13C NMR (CDCl3, TMS) d = 21.3, 22.1, 72.2, 126.0, 128.0,
128.4, 141.6, 170.2; HRMS (ESI) calcd for C10H12O2Na [M+Na]+: m/z 187.0730,
found m/z 187.0728.
4-(
a
-Benzoyloxy)ethyl-N,N-dimethylbenzamide (C18H19O3N): IR (Neat): 1112,
1270, 1633, 1715, 3471 cmÀ1
;
1H NMR (CDCl3, TMS) d = 1.67 (d, J = 6.6 Hz, 3H),
3.04 (br, 6H), 6.14 (q, J = 6.6 Hz, 1H), 7.41 (t, J = 7.1 Hz, 2H), 7.44 (t, J = 7.4 Hz,
4H), 7.56 (t, J = 7.1 Hz, 1H), 8.08 (d, J = 7.1 Hz, 2H); 13C NMR (CDCl3, TMS)
d = 22.4, 35.3, 39.6, 72.4, 126.0, 127.3, 128.4, 129.6, 130.3, 133.0, 135.8, 143.2,
165.7, 171.2; HRMS (ESI) calcd for C18H19O3NNa [M+Na]+: m/z 320.1257, found
m/z 320.1261.
(a ;
-Benzoyloxy)ethylbenzene (C15H14O2): IR (Neat): 1109, 1267, 1713 cmÀ1 1H
NMR (CDCl3, TMS) d = 1.67 (d, J = 6.6 Hz, 3H), 6.13 (q, J = 6.6 Hz, 1H), 7.29 (t,
J = 7.3 Hz, 1H), 7.36 (t, J = 7.5 Hz, 2H), 7.41–7.44 (m, 4H), 7.55 (t, J = 7.5 Hz, 1H),
8.07 (d, J = 7.5 Hz, 2H); 13C NMR (CDCl3, TMS) d = 22.4, 72.9, 126.0, 127.8, 128.3,
128.5, 129.6, 130.5, 132.9, 141.7, 165.7; HRMS (ESI) calcd for C15H14O2Na
[M+Na]+: m/z 249.0886, found m/z 249.0882.
(a ;
-Acetoxy)propylbenzene (C11H14O2): IR (Neat): 1072, 1236, 1736 cmÀ1 1H
NMR (CDCl3, TMS) d = 0.87 (t, J = 7.4 Hz, 3H), 1.74–1.96 (m, 2H), 2.07 (s, 3H),
5.66 (t, J = 6.9 Hz, 1H), 7.27–7.36 (m, 5H); 13C NMR(CDCl3, TMS) d = 9.8, 21.2,
29.2, 77.3, 126.5, 127.8, 128.3, 140.5, 170.4; HRMS (ESI) calcd for C11H14O2Na
[M+Na]+: m/z 201.0886, found m/z 201.0887.
4-(
a-Acetoxy)ethyl-1-bromobenzene (C10H11O2Br): IR (Neat): 599, 1071, 1241,
1735 cmÀ1
;
1H NMR (CDCl3, TMS) d = 1.51 (d, J = 6.7 Hz, 3H), 2.06 (s, 3H), 5.82
(q, J = 6.7 Hz, 1H), 7.22 (d, J = 8.3 Hz, 2H), 7.47 (d, J = 8.3 Hz, 2H); 13C
NMR(CDCl3, TMS) d = 21.2, 22.1, 71.6, 121.7, 127.8, 131.6, 140.7, 170.1;
HRMS(APPI) calcd for C10H10O2Br [MÀH]+: m/z 240.9859, found m/z 240.9854.
(a ;
-Benzoyloxy)propylbenzene (C16H16O2): IR (Neat): 1111, 1271, 1719 cmÀ1
1H NMR (CDCl3, TMS) d = 0.97 (t, J = 7.4 Hz, 3H), 1.91–2.01 (m, 1H), 2.01–2.12
(m, 1H), 5.92 (t, J = 6.9 Hz, 1H), 7.28 (t, J = 7.3 Hz, 1H), 7.34 (t, J = 7.3 Hz, 2H),
7.42 (d, J = 7.3 Hz, 2H), 7.44 (t, J = 7.4 Hz, 2H), 7.56 (t, J = 7.4 Hz, 1H), 8.09 (d,
J = 7.4 Hz, 2H); 13C NMR(CDCl3, TMS) d = 10.0, 29.5, 77.9, 126.4, 127.8, 128.3,
128.4, 129.6, 130.5, 132.9, 140.6, 165.9; HRMS (ESI) calcd for C16H16O2Na
[M+Na]+: m/z 263.1043, found m/z 263.1046.
4-(
a-Benzoyloxy)ethyl-1-bromobenzene (C15H13O2Br): IR (Neat): 711, 1109,
1270, 1718 cmÀ1
;
1H NMR (CDCl3, TMS) d = 1.65 (d, J = 6.6 Hz, 3H), 6.07 (q,
J = 6.6 Hz, 1H), 7.32 (d, J = 8.5 Hz, 2H), 7.44 (t, J = 7.5 Hz, 2H), 7.48 (d, J = 8.5 Hz,
2H), 7.56 (t, J = 7.5 Hz, 1H), 8.06 (d, J = 7.5 Hz, 2H); 13C NMR (CDCl3, TMS)
d = 22.2, 72.2, 121.7, 127.7, 128.3, 129.6, 130.2, 131.6, 133.0, 140.8, 165.6;
HRMS(APPI) calcd for C15H12O2Br [MÀH]+: m/z 303.0015, found m/z 303.0010.
(a ;
-Acetoxy)butylbenzene (C12H16O2): IR (Neat): 1025, 1237, 1736 cmÀ1 1H
1-(
a
-Acetoxy)ethyl-4-t-butylbenzene (C14H20O2): IR (Neat): 1064, 1242,
NMR (CDCl3, TMS) d = 0.92 (t, J = 7.4 Hz, 3H), 1.21–1.41 (m, 2H), 1.70–1.80 (m,
1H), 1.86–1.93 (m, 1H), 2.07 (s, 3H), 5.74 (t, J = 6.3 Hz, 1H), 7.25–7.36 (m, 5H);
13C NMR(CDCl3, TMS) d = 13.8, 18.8, 21.3, 38.4, 75.9, 126.5, 127.8, 128.4, 140.8,
170.4; HRMS (ESI) calcd for C12H16O2Na [M+Na]+: m/z 215.1043, found m/z
215.1041.
1743 cmÀ1
;
1H NMR (CDCl3, TMS) d = 1.33 (s, 9H), 1.53 (d, J = 6.6 Hz, 3H),
2.07 (s, 3H), 5.88 (q, J = 6.6 Hz, 1H), 7.28 (d, J = 8.6 Hz, 2H), 7.37 (d, J = 8.6 Hz,
2H); 13C NMR (CDCl3, TMS) d = 21.3, 21.9, 31.3, 34.4, 72.1, 125.3, 125.8, 138.5,
150.7, 170.3; HRMS (ESI) calcd for C14H20O2Na [M+Na]+: m/z 243.1356, found
m/z 243.1353.
(a ;
-Benzoyloxy)butylbenzene (C17H18O2): IR (Neat): 1111, 1272, 1718 cmÀ1 1H
1-(
a
-Benzoyloxy)ethyl-4-t-butylbenzene (C19H22O2): IR (Neat): 1110, 1270,
NMR (CDCl3, TMS) d = 0.95 (t, J = 7.4 Hz, 3H), 1.31–1.51 (m, 2H), 1.83–1.92 (m,
1H), 2.02–2.11 (m, 1H), 5.99 (t, J = 6.1 Hz, 1H), 7.28 (t, J = 7.3 Hz, 1H), 7.35 (t,
J = 7.3 Hz, 2H), 7.42 (d, J = 7.3 Hz, 2H), 7.44 (t, J = 7.5 Hz, 2H), 7.58 (t, J = 7.5 Hz,
1H), 8.08 (d, J = 7.5 Hz, 2H); 13C NMR (CDCl3, TMS) d = 13.8, 18.8, 38.7, 76.5,
126.4, 127.8, 128.3, 128.4, 129.6, 130.5, 132.9, 140.9, 165.8; HRMS (ESI) calcd
for C17H18O2Na [M+Na]+: m/z 277.1199, found m/z 277.1202.
1719 cmÀ1
;
1H NMR (CDCl3, TMS) d = 1.31 (s, 9H), 1.66 (d, J = 6.6 Hz, 3H), 6.13
(q, J = 6.6 Hz, 1H), 7.36–7.39 (m, 4H), 7.42 (t, J = 7.4 Hz, 2H), 7.54 (t, J = 7.4 Hz,
1H), 8.07 (d, J = 7.4 Hz, 2H); 13C NMR(CDCl3, TMS) d = 22.2, 31.3, 34.5, 72.7,
125.4, 125.8, 128.3, 129.6, 130.6, 132.8, 138.6, 150.8, 165.8; HRMS (ESI) calcd
for C19H22O2Na [M+Na]+: m/z 305.1512, found m/z 305.1509.
1-(
a
-Acetoxy)ethyl-4-ethylbenzene (C12H16O2): IR (Neat): 1064, 1240,
1,3-Diacetoxy-1-phenylpropane (C13H16O4): IR (Neat): 1043, 1236, 1743 cmÀ1
;
1738 cmÀ1
;
1H NMR (CDCl3, TMS) d = 1.23 (t, J = 7.8 Hz, 3H), 1.53 (d,
1H NMR (CDCl3, TMS) d = 2.04 (s, 3H), 2.06 (s, 3H), 2.06–2.15 (m, 1H), 2.21–2.30
(m, 1H), 3.98–4.04 (m, 1H), 4.10–4.19 (m, 1H), 5.85 (dd, J = 8.3 and 5.7 Hz, 1H),
7.27–7.36 (m, 5H); 13C NMR (CDCl3, TMS) d = 20.7, 21.0, 35.1, 60.5, 72.7, 126.3,
128.0, 128.5, 139.8, 170.0, 170.1; HRMS (ESI) calcd for C13H16O4Na [M+Na]+:
m/z 259.0941, found m/z 259.0938.
J = 6.6 Hz, 3H), 2.06 (s, 3H), 2.64 (q, J = 7.8 Hz, 2H), 5.86 (q, J = 6.6 Hz, 1H),
7.18 (d, J = 7.9 Hz, 2H), 7.27 (d, J = 7.9 Hz, 2H); 13C NMR(CDCl3, TMS) d = 15.4,
21.3, 22.0, 28.5, 72.1, 126.1, 127.9, 138.8, 143.9, 170.3; HRMS (ESI) calcd for
C
12H16O2Na [M+Na]+: m/z 215.1043, found m/z 215.1040.

H. Baba et al. / Tetrahedron Letters 52 (2011) 4303–4307
4307
3-Acetoxy-1-benzoyloxy-1-phenylpropane (C18H18O4): IR (Neat): 1111,
1272, 1720 cmÀ1 1H NMR (CDCl3, TMS) d = 2.00 (s, 3H), 2.20–2.30 (m, 1H),
4-(
a
-Acetoxy)pentylbiphenyl (C19H22O2): IR (Neat): 1108, 1271, 1719 cmÀ1 1H
;
;
NMR (CDCl3, TMS) d = 0.89 (t, J = 7.1 Hz, 3H), 1.20–1.30 (m, 1H), 1.30–1.39 (m,
3H), 1.76–1.84 (m, 1H), 1.90–1.98 (m, 1H), 2.09 (s, 3H), 5.76 (t, J = 7.0 Hz, 1H),
7.35 (t, J = 7.5 Hz, 1H), 7.40 (d, J = 7.5 Hz, 2H), 7.44 (t, J = 7.5 Hz, 2H), 7.58 (t,
J = 7.9 Hz, 4H); 13C NMR(CDCl3, TMS) d = 13.9, 21.3, 22.4, 27.7, 36.0, 75.9, 127.0,
127.1, 127.2, 127.3, 128.7, 137.8, 139.8, 140.7, 170.4; HRMS (ESI) calcd for
2.38–2.47 (m, 1H), 4.09–4.16 (m, 1H), 4.19–4.28 (m, 1H), 6.12 (dd, J = 8.1 and
5.4 Hz, 1H), 7.31 (t, J = 7.2 Hz, 1H), 7.36 (t, J = 7.2 Hz, 2H), 7.40–7.48 (m, 4H),
7.60 (t, J = 7.3 Hz, 1H), 8.07 (d, J = 7.3 Hz, 2H); 13C NMR(CDCl3, TMS) d = 20.9,
35.4, 60.8, 73.5, 126.3, 128.2, 128.4, 128.6, 129.6, 130.1, 133.1, 139.9, 165.6,
171.0; HRMS (ESI) calcd for C18H18O4Na [M+Na]+:m/z 321.1097, found m/z
321.1092.
C
19H22O2Na [M+Na]+: m/z 305.1512, found m/z 305.1510.
4-(
1719 cmÀ1
a-Benzoyloxy)pentylbiphenyl (C24H24O2): IR (Neat): 1108, 1271,
1-Acetoxy-4-bromo-1-phenylbutane (C12H15O2Br): IR (Neat): 1026, 1235,
;
1H NMR (CDCl3, TMS) d = 0.91 (t, J = 7.1 Hz, 3H), 1.30–1.48 (m,
1735 cmÀ1
;
1H NMR (CDCl3, TMS) d = 1.77–1.86 (m, 1H), 1.86–2.01 (m, 2H),
4H), 1.90–1.99 (m, 1H), 2.06–2.15 (m, 1H), 6.02 (t, J = 6.1 Hz, 1H), 7.34 (t,
J = 7.3 Hz, 1H), 7.40–7.51 (m, 6H), 7.54–7.60 (m, 5H), 8.10 (d, J = 7.3 Hz, 2H);
13C NMR(CDCl3, TMS) d = 14.0, 22.5, 27.7, 36.3, 76.5, 126.9, 127.0, 127.1, 127.2,
127.3, 128.3, 128.7, 129.6, 130.5, 132.9, 140.0, 140.8, 165.9; HRMS (ESI) calcd
for C24H24O2Na [M+Na]+: m/z 367.1669, found m/z 367.1667.
2.01–2.08 (m, 1H), 2.09 (s, 3H), 3.40 (t, J = 6.5 Hz, 2H), 5.76 (dd, J = 7.6 and
5.6 Hz, 1H), 7.28–7.39 (m, 5H); 13C NMR(CDCl3, TMS) d = 21.2, 28.7, 33.1, 34.8,
75.0, 126.4, 128.1, 128.5, 140.1, 170.3; HRMS(APPI) calcd for
C12H14O2Br
[MÀH]+: m/z 269.0172, found m/z 269.0196.
1-Benzoyloxy-4-bromo-1-phenylbutane (C17H17O2Br): IR (Neat): 1109, 1271,
9-Acetoxy-9H-fluorene (C15H12O2): IR (Neat): 1024, 1234, 1737 cmÀ1 1H NMR
;
1719 cmÀ1
;
1H NMR (CDCl3, TMS) d = 1.87–2.29 (m, 4H), 3.43 (t, J = 6.6 Hz, 2H),
(CDCl3, TMS) d = 2.19 (s, 3H), 6.80 (s, 1H), 7.30 (t, J = 7.6 Hz, 2H), 7.41 (t,
J = 7.6 Hz, 2H), 7.55 (d, J = 7.6 Hz, 2H), 7.67 (d, J = 7.6 Hz, 2H); 13C NMR(CDCl3,
TMS) d = 21.2, 75.1, 120.1, 125.8, 127.8, 129.4, 141.0, 142.0, 171.7; HRMS (ESI)
calcd for C15H12O2Na [M+Na]+: m/z 240.0730, found m/z 247.0733.
6.03 (dd, J = 7.8 and 5.5 Hz, 1H), 7.30 (t, J = 7.0 Hz, 1H), 7.36 (t, J = 7.0 Hz, 2H),
7.42 (d, J = 7.0 Hz, 2H), 7.45 (t, J = 7.6 Hz, 2H), 7.57 (t, J = 7.6 Hz, 1H), 8.08 (d,
J = 7.6 Hz, 2H); 13C NMR(CDCl3, TMS) d = 28.7, 33.2, 35.1, 75.6, 126.3, 128.1,
128.4, 128.6, 129.6, 130.2, 133.1, 140.2, 165.7; HRMS(APPI) calcd for
9-Benzoyloxy-9H-fluorene (C20H14O2): IR (Neat): 1262, 1451, 1724 cmÀ1 1H
;
C
17H16O2Br [MÀH]+: m/z 331.0328, found m/z 331.0351.
NMR (CDCl3, TMS) d = 7.05 (s, 1H), 7.31 (t, J = 7.8 Hz, 2H), 7.41–7.47 (m, 4H),
7.57 (t, J = 7.4 Hz, 1H), 7.63 (d, J = 7.8 Hz, 2H), 7.71 (d, J = 7.8 Hz, 2H), 8.09 (d,
J = 7.4 Hz, 2H); 13C NMR(CDCl3, TMS) d = 75.7, 120.2, 126.2, 128.0, 128.5, 128.6,
129.6, 130.1, 133.3, 141.2, 142.3, 167.4; HRMS (ESI) calcd for C20H14O2Na
[M+Na]+: m/z 309.0886, found m/z 309.0888.
(a
-Acetoxy)octylbenzene (C16H24O2): IR (Neat): 1022, 1237, 1738 cmÀ1 1H
;
NMR (CDCl3, TMS) d = 0.86 (t, J = 7.0 Hz, 3H), 1.15–1.38 (m, 10H), 1.71–1.79 (m,
1H), 1.84–1.94 (m, 1H), 2.06 (s, 3H), 5.72 (t, J = 6.5 Hz, 1H), 7.26–7.35 (m, 5H);
13C NMR(CDCl3, TMS) d = 14.0, 21.3, 22.6, 25.5, 29.1, 29.3, 31.7, 36.3, 76.1,
126.5, 127.8, 128.4, 140.8, 170.4; HRMS (ESI) calcd for C16H24O2Na [M+Na]+: m/
z 271.1669, found m/z 271.1666.
Diphenylmethyl acatate (C15H14O2): IR (Neat): 1023, 1232, 1741 cmÀ1 1H
;
NMR (CDCl3, TMS) d = 2.16 (s, 3H), 6.88 (s, 1H), 7.26–7.36 (m, 10H); 13C
NMR(CDCl3, TMS) d = 21.3, 76.8, 127.0, 127.9, 128.5, 140.2, 170.0; HRMS (ESI)
calcd for C15H14O2Na [M+Na]+:m/z 249.0886, found m/z 249.0886.
(a
-Benzoyloxy)octylbenzene (C21H26O2): IR (Neat): 1109, 1271, 1720 cmÀ1;1H
NMR (CDCl3, TMS) d = 0.86 (t, J = 6.9 Hz, 3H), 1.17–1.46 (m, 10H), 1.86–1.92 (m,
1H), 2.01–2.10 (m, 1H), 5.97 (t, J = 6.9 Hz, 1H), 7.29 (t, J = 7.2 Hz, 1H), 7.35 (t,
J = 7.2 Hz, 2H), 7.42 (d, J = 7.2 Hz, 2H), 7.45 (t, J = 7.3 Hz, 2H), 7.56 (t, J = 7.3 Hz,
1H), 8.08 (d, J = 7.3 Hz, 2H); 13C NMR(CDCl3, TMS) d = 14.1, 22.6, 25.5, 29.1, 29.3,
31.8, 36.5, 76.7, 126.4, 127.8, 128.3, 128.4, 129.6, 130.5, 132.9, 140.9,
165.9; HRMS (ESI) calcd for C21H26O2Na [M+Na]+: m/z 333.1825, found m/z
333.1819.
Diphenylmethyl benzoate (C20H16O2): IR (Neat): 1107, 1265, 1712 cmÀ1 1H
;
NMR (CDCl3, TMS) d = 7.12 (s, 1H), 7.29 (t, J = 7.3 Hz, 2H), 7.32–7.38 (m, 4H),
7.42–7.47 (m,
NMR(CDCl3, TMS) d = 77.3, 127.0, 127.8, 128.3, 128.4, 129.6, 129.9, 133.0,
140.2, 165.4; HRMS (ESI) calcd for C20H16O2Na [M+Na]+: m/z 311.1043, found
m/z 311.1041.
6
H), 7.57 (t, J = 7.3 Hz, 1H), 8.14 (d, J = 7.3 Hz, 2H); 13C