Site-selective suzuki-miyaura reactions of the bis(triflate) of 5,10-dihydroxy-11 H -benzo[ b ]fluoren-11-one

Article abstract of DOI:10.1055/s-0030-1259076

5,10-Diaryl-11H-benzo[b]fluoren-11-ones were prepared by Suzuki-Miyaura reactions of the bis(triflate) of 5,10-dihydroxy-11H-benzo[b]fluoren-11-one. The reactions proceed with excellent site-selectivity. The first attack occurs at position 10, due to elec

Full text of DOI:10.1055/s-0030-1259076

LETTER
3031
Site-Selective Suzuki–Miyaura Reactions of the Bis(triflate) of 5,10-dihydroxy-
11H-benzo[b]fluoren-11-one
Suzuki–Miyaura
R
h
eactions of
B
a
is(triflate)
z
of 5,10-dih
w
ydroxy-11
H
-benzo
a
[
b
]
fluoren-
n
11-one Ali Salman,a Munawar Hussain,a Alexander Villinger,a Peter Langer*a,b
a
Institut für Chemie, Universität Rostock, Albert Einstein Str. 3a, 18059 Rostock, Germany
Leibniz-Institut für Katalyse an der Universität Rostock e.V., Albert Einstein Str. 29a, 18059 Rostock, Germany
Fax +49(381)4986412; E-mail: peter.langer@uni-rostock.de
b
Received 19 October 2010
have recently reported a synthetic approach to functional-
ized fluorenones based on formal [3+3]-cyclizations of
1,3-bis(silyloxy)-1,3-butadienes.16 Due to the importance
of fluorenones and benzofluorenones, the development of
efficient and regioselective methods for the synthesis of
aryl-substituted derivatives is of considerable current
importance. Herein, we report a convenient approach
to 5,10-diaryl-11H-benzo[b]fluoren-11-ones by site-
selective17 Suzuki–Miyaura reactions of the bis(triflate)18
of 5,10-dihydroxy-11H-benzo[b]fluoren-11-one. These
reactions provide a convenient access to products which
are difficult to prepare by other methods.
Abstract: 5,10-Diaryl-11H-benzo[b]fluoren-11-ones were pre-
pared by Suzuki–Miyaura reactions of the bis(triflate) of 5,10-dihy-
droxy-11H-benzo[b]fluoren-11-one. The reactions proceed with
excellent site-selectivity. The first attack occurs at position 10, due
to electronic reasons.
Key words: catalysis, palladium, Suzuki–Miyaura reaction, regio-
selectivity, fluorenones
Natural and synthetic fluorenones exhibit a broad spec-
trum of biological activities and also occur in many natu-
ral products. This includes, for example, dengibsin,
dengibsinin, or dendroflorin isolated from the orchidee
Dendrobium gibsonii Lindl.1 Fluorenones are of great
pharmacological importance.2 They have been used as
probes for the redox activity of DNA.3 Amidofluorenone
derivatives have been shown to act as telomerase inhibi-
tors.4 Kinamycin derivatives of the family of kinamycin
natural products have been reported to display antitumor
and antimicrobial activity against Gram-positive bacte-
ria.5 In recent years, new kinamycin analogues, containing
a 6,6,5,6-ring system, have also been isolated. For exam-
ple, kinafluorenone (A; Figure 1) was found to be a major
metabolite of a mutant strain of Streptomyces mu-
rayamaensis. The fluorenone alkaloid cauliphine (B;
Figure 1), which possesses antimyocardial ischemia ac-
tivity, has also been isolated from Caulophyllum robust-
um.6 Arylated fluorenones, fluorenes and benzo-
fluorenones along with their oligomers and polymers have
been studied extensively for the development of organic
light-emitting devices (OLEDs).7 Fluorenones are also
important compounds in photochemistry.8
HO
HO
OH
Me
N
OH
Me
O
O
MeO
OH
OMe
A
B
Figure 1 Fluorenone natural products: A: a major metabolite isola-
ted from mutant strain of Streptomyces murayamaensis; B: cauliphine,
a fluorenone alkaloid with antimyocardial ischemia activity
The reaction of 5,10-dihydroxy-11H-benzo[b]fluoren-11-
one (1) with triflic anhydride (2.4 equiv) afforded the
bis(triflate) 2 (Scheme 1).19
OH
OTf
i
OH
O
OTf
O
Fluorenones have been prepared by intramolecular
Friedel–Crafts acylations of biaryls,9 by [4+2]-cycloaddi-
tions of conjugated enynes,10 by oxidation of fluorenes,11
based on remote aromatic metalations,12 by reaction of
malonic acid dinitrile with aromatic aldehydes and meth-
ylketones,13 by Suzuki reaction of boronic acids of benzo-
ic acid amides with aryl triflates and subsequent
cyclization,14 by acid-mediated intramolecular Friedel–
Crafts cyclization of 2-methoxycarbonylbiaryls, and by
Suzuki reactions of salicylate-derived enol triflates.15 We
2
1
Scheme 1 Synthesis of 2. Reagents and conditions: (i) CH2Cl2, 1
(1.0 equiv), –78 °C, pyridine (4.0 equiv), Tf2O (2.4 equiv), –78 → 20
°C, 14 h.
The Suzuki–Miyaura reaction of 2 with arylboronic acids
3a–f (2.4 equiv) afforded the 5,10-diaryl-11H-ben-
zo[b]fluoren-11-ones 4a–f in 70–85% yield (Scheme 2,
Table 1). The yield of product 4c, derived from the (less
reactive) electron-poor arylboronic acid 3c, was lower
than the yields of the other products. The best yields were
obtained when the reactions were carried out using
SYNLETT 2010, No. 20, pp 3031–3034
x
x
.x
x
.2
0
1
1
Advanced online publication: 25.11.2011
DOI: 10.1055/s-0030-1259076; Art ID: G31610ST
© Georg Thieme Verlag Stuttgart · New York

3032
G. A. Salman et al.
LETTER
OTf
Table 2 Synthesis of 5a–i
Ar
Ar
ArB(OH)2
Yield of 5 (%)a
3a–f
3
a
b
c
d
e
f
5
a
b
c
d
e
f
Ar
i
4-MeOC6H4
4-t-BuC6H4
4-ClC6H4
90
76
78
87
80
85
88
75
70
OTf
O
O
2
4a–f
Scheme 2 Synthesis of 4a–f. Reagents and conditions: (i) 2 (1.0
equiv), 3a–f (2.2 equiv), Pd(PPh3)4 (6 mol%), K3PO4 (3.0 equiv), 1,4-
dioxane, 90 °C, 10 h.
3,5-Me2C6H3
3-MeC6H4
4-EtC6H4
Table 1 Synthesis of 4a–f
3,4
a
Ar
Yield of 4 (%)a
g
h
i
g
h
i
3,5-(MeO)2C6H3
4-FC6H4
4-MeOC6H4
4-t-BuC6H4
4-ClC6H4
3,5-Me2C6H3
3-MeC6H4
4-EtC6H4
80
75
70
85
78
75
b
c
4-CF3C6H4
a Yields of isolated products.
d
e
Ar2
OTf
1) Ar1B(OH)2
2) Ar2B(OH)2
f
i, ii
a Yields of isolated products.
OTf
O
Ar1
O
6a–e
2
Pd(PPh3)4 as the catalyst and K3PO4 as the base and when
1,4-dioxane was used as the solvent.20,21
Scheme 4 Synthesis of 6a–e. Reagents and conditions: (i) 2 (1.0
equiv), 3a,b,g (1.0 equiv), Pd(PPh3)4 (3 mol%), K3PO4 (3 equiv), 1,4-
dioxane, 60 °C, 10 h; (ii) 3b,d,e,f (1.1 equiv), Pd(PPh3)4 (3 mol%), 90
°C, 10 h.
The Suzuki–Miyaura reaction of 2 with arylboronic acids
3a–i (1.0 equiv) afforded the 10-aryl-5-trifluoromethyl-
sulfonyloxy-11H-benzo[b]fluoren-11-ones 5a–i in good
yields (Scheme 3, Table 2).20,22 The yields of reactions of
electron-rich arylboronic acids were higher than those of
electron-poor arylboronic acids. During the optimization,
it proved to be important to carry out the reaction at 60 °C
instead of 90 °C.
Table 3 Synthesis of 6a–e
3
6
a
b
c
Ar1
Ar2
Yield of 6 (%)a
a,d
g,b
g,e
b,d
g,f
4-MeOC6H4
3,4-(MeO)2C6H3
3,4-(MeO)2C6H3
4-t-BuC6H4
3,5-Me2C6H3
4-t-BuC6H4
3-MeC6H4
3,5-Me2C6H3
4-EtC6H4
72
75
77
80
65
OTf
OTf
ArB(OH)2
3a–i
i
d
e
OTf
O
Ar
O
3,4-(MeO)2C6H3
2
5a–i
a Yields of isolated products.
Scheme 3 Synthesis of 5a–i. Reagents and conditions: (i) 2 (1.0
equiv), 3a–i (1.1 equiv), Pd(PPh3)4 (3 mol%), K3PO4 (2 equiv), 1,4-
dioxane, 60 °C, 10 h.
The first attack of palladium(0)-catalyzed cross-coupling
reactions generally occurs at the electronically more defi-
cient and sterically less hindered position.25 Position 10 of
bis(triflate) 2 is sterically more hindered than position 5
because of the neighborhood of the carbonyl group
(Scheme 5). Therefore, the site-selective formation of 5a–
i and 6a–e can be explained by electronic reasons. In ad-
dition, chelation of the catalyst by the carbonyl group
might play a role. A related site-selectivity has been pre-
viously observed for the bis(triflates) of alizarin and phe-
nyl 1,4-dihydroxynaphthoate.18b,d
The one-pot reaction of 2 with two different arylboronic
acids (sequential addition) afforded the 5,10-diaryl-11H-
benzo[b]fluoren-11-ones 6a–e containing two different
aryl groups (Scheme 4, Table 3).20,23 During the optimiza-
tion, it proved to be important to carry out the first step of
the one-pot reaction at 60 °C and the second step at 90 °C.
All products were characterized by spectroscopic meth-
ods. The constitution was established by 2D NMR exper-
iments (HMBC, NOESY). The structure of 5a was
independently confirmed by X-ray crystal structure anal-
ysis (Figure 2).24
In conclusion, we have reported an efficient synthesis of
5,10-diaryl-11H-benzo[b]fluoren-11-ones by Suzuki–
Miyaura reactions of the bis(triflate) of 5,10-dihydroxy-
Synlett 2010, No. 20, 3031–3034 © Thieme Stuttgart · New York

LETTER
Suzuki–Miyaura Reactions of the Bis(triflate) of 5,10-dihydroxy-11H-benzo[b]fluoren-11-one
3033
(6) Wang, S.; Wen, B.; Wang, N.; Liu, J.; He, L. Arch. Pharm.
Res. 2009, 32, 2009.
(7) Goel, A.; Chaurasia, S.; Dixit, M.; Kumar, V.; Parakash, S.;
Jena, B.; Verma, J. K.; Jain, M.; Anand, R. S.; Manoharan,
S. Org. Lett. 2009, 11, 1289; and references cited therein.
(8) Tilly, D.; Samanta, S. S.; Faigl, F.; Mortier, J. Tetrahedron
Lett. 2002, 43, 8347.
(9) (a) Underwood, H. W.; Kochmann, E. L. J. Am. Chem. Soc.
1924, 46, 2073. (b) Lemal, D. M.; Gosselink, E. P.;
McGregor, S. D. J. Am. Chem. Soc. 1966, 88, 582.
(c) Bandyopadhyay, T. K.; Bhattacharya, A. J. Indian J.
Chem. Sect. B 1980, 19, 439. (d) Kym, P. R.; Hummert,
K. L.; Nilsson, A. G.; Lubin, M.; Katzenellenbogen, J. A.
J. Med. Chem. 1996, 39, 4897. (e) Gruber, J.; Li, R. W. C.;
Aguiar, L. H.; Benvenho, J. M. C.; Adriano, R. V.;
Lessmann, R.; Huemmelgen, I. A. J. Mater. Chem. 2005, 15,
517. (f) Olah, G. A.; Mathew, T.; Farnia, M.; Prakash, S.
Synlett 1999, 1067.
(10) Danheiser, L. R.; Gould, E. A.; Pradilla, F. R.; Helgason,
L. A. J. Org. Chem. 1994, 59, 5514.
(11) (a) Murahashi, S.-I.; Komiya, N.; Oda, Y.; Kuwabara, T.;
Naota, T. J. Org. Chem. 2000, 65, 9186. (b) Lippert, E.;
Walter, H. Angew. Chem. 1959, 71, 429.
Figure 2 Crystal structure of 5a
(12) Fu, J.-M.; Zhao, B.-P.; Sharp, M. J.; Snieckus, V. J. Org.
Chem. 1991, 56, 1683.
(13) Yu, Z.; Velasco, D. Tetrahedron Lett. 1999, 40, 3229.
(14) Ciske, F. L.; Jones, W. D. Jr. Synthesis 1998, 1195.
(15) Schmidt, J. M.; Tremblay, G. B.; Page, M.; Mercure, J.;
Feher, M.; Dunn-Dufault, R.; Peter, M. G.; Redden, P. R.
J. Med. Chem. 2003, 46, 1289.
sterically less hindered
electronically less deficient
OTf
OTf
O
(16) Reim, S.; Lau, M.; Adeel, M.; Hussain, I.; Yawer, M. A.;
Riahi, A.; Ahmed, Z.; Fischer, C.; Reinke, H.; Langer, P.
Synthesis 2009, 445.
sterically more hindered
electronically more deficient
(17) For reviews of cross-coupling reactions of polyhalogenated
heterocycles, see: (a) Schröter, S.; Stock, C.; Bach, T.
Tetrahedron 2005, 61, 2245. (b) Schnürch, M.; Flasik, R.;
Khan, A. F.; Spina, M.; Mihovilovic, M. D.; Stanetty, P. Eur.
J. Org. Chem. 2006, 3283.
Scheme 5 Possible explanation for the site-selectivity of the reac-
tions of bis(triflate) 2
11H-benzo[b]fluoren-11-one. The site-selectivity in favor
(18) For Suzuki–Miyaura reactions of bis(triflates) from our
laboratory, see, for example: (a) Methyl 2,5-dihydroxy-
benzoate: Nawaz, M.; Ibad, M. F.; Abid, O.-U.-R.;
Khera, R. A.; Villinger, A.; Langer, P. Synlett 2010, 150.
(b) Alizarin: Mahal, A.; Villinger, A.; Langer, P. Synlett
2010, 1085. (c) 3,4-Dihydroxybenzophenone: Nawaz, M.;
Khera, R. A.; Malik, I.; Ibad, M. F.; Abid, O.-U. R.;
Villinger, A.; Langer, P. Synlett 2010, 979. (d) Phenyl 1,4-
dihydroxynaphthoate: Abid, O.-U.-R.; Ibad, M. F.; Nawaz,
M.; Ali, A.; Sher, M.; Rama, N. H.; Villinger, A.; Langer, P.
Tetrahedron Lett. 2010, 51, 1541.
of position 10 can be explained by electronic reasons.
Acknowledgment
Financial support by the DAAD (scholarship for G.A.S.) and by the
States of Pakistan and Mecklenburg-Vorpommern (scholarships for
M. H.) is gratefully acknowledged.
References and Notes
(19) Synthesis of 11-Oxo-11H-benzo[b]fluorene-5,10-diyl
Bis(trifluoromethanesulfonate) (2): To a solution of 1 (2.0
g, 7.6 mmol) in CH2Cl2 (80 mL) was added pyridine (2.5
mL, 30.5 mmol), at 20 °C under an argon atmosphere. After
stirring for 10 min, Tf2O (3.0 mL, 18 mmol) was added at
–78 °C. The mixture was allowed to warm to 20 °C and
stirred overnight. The reaction mixture was filtered and the
filtrate was concentrated in vacuo. The residue was purified
by chromatography (flash silica gel, heptanes–EtOAc)
without aqueous work up to give 2 as a yellow solid (3.5 g,
88%); mp 186–188 °C. 1H NMR (300 MHz, CDCl3): d =
7.43 (t, 1 H, J = 7.7 Hz, ArH), 7.59–7.79 (m, 4 H, ArH), 8.01
(1) (a) Talapatra, S. K.; Bose, S.; Malliks Asok, K.; Talapatra,
B. Tetrahedron 1985, 41, 2765. (b) Sargent, M. V. J. Chem.
Soc., Perkin Trans. 1 1987, 2553. (c) Fan, C.; Wang, W.;
Wang, Y.; Qin, G.; Zhao, W. Phytochemistry 2001, 57,
1255. (d) Wu, X. Y.; Qin, G. W.; Fan, D. J.; Xu, R. S.
Phytochemistry 1994, 36, 477.
(2) Campo, M. A.; Larock, R. C. J. Org. Chem. 2002, 67, 5616;
and references cited therein.
(3) Tierney, M. T.; Grinstaff, M. W. J. Org. Chem. 2000, 65,
5355.
(4) Perry, P. J.; Read, M. A.; Davies, R. T.; Gowan, S. M.;
Reszka, A. P.; Wood, A. A.; Kelland, L. R.; Neidle, S.
J. Med. Chem. 1999, 42, 2679.
(5) (a) Gould, S. J.; Melville, C. R.; Cone, M. C.; Chen, J.;
Carney, J. R. J. Org. Chem. 1997, 62, 320. (b) Mal, D.;
Hazra, N. K. Tetrahedron Lett. 1996, 37, 2641; and
references cited therein. (c) Cragoe, E. J.; Marangos, P. J.;
Weimann, T. R. U.S. Patent, 6251898 BI, 2001.
(t, 2 H, J = 8.0 Hz, ArH), 8.10 (d, 1 H, J = 8.3 Hz, ArH). 19
NMR (282.4 MHz, CDCl3): d = –72.29, –72.3. 13C NMR
(75.5 MHz, CDCl3): d = 118.6 (q, JF,C = 320.5 Hz, CF3),
F
118.7 (q, JF,C = 321.4 Hz, CF3), 122.8, 124.0, 125.36 (CH),
128.2 (C), 129.4, 131.2, 131.3 (CH), 132.0, 135.7 (C), 135.9
(CH), 136.8, 140.2, 141.2 (C), 187.2 (CO). IR (KBr): 3085,
Synlett 2010, No. 20, 3031–3034 © Thieme Stuttgart · New York

3034
G. A. Salman et al.
LETTER
2926, 2854 (w), 1721 (m), 1635, 1600, 1591, 1581, 1516,
1466 (w), 1435, 1405 (m), 1391, 1337, 1289, 1274, 1241
(w), 1203 (s), 1173 (m), 1128 (s), 1082 (m), 1043 (w), 1011,
975 (m), 891 (s), 865, 814, 782 (m), 760, 747, 722 (s), 688
(m), 662, 651, 638 (w), 621, 595, 590 (s), 570, 528 (m) cm–
1. GC–MS (EI, 70 eV): m/z (%) = 526 (53) [M+], 393 (77),
329 (99), 301 (100). HRMS (EI, 70 eV): m/z calcd for
C19H8O7S2F6: 525.96101; found: 525.961568
–72.47. 13C NMR (75.5 MHz, CDCl3): d = 55.9, 56.0 (OMe),
110.9, 112.9 (CH), 118.7 (q, JF,C = 321.6 Hz, CF3), 122.1,
124.5, 125.0 (CH), 126.6 (C), 128.0 (CH), 129.4 (C), 129.5,
129.9 (CH), 130.3 (C), 130.4 (CH), 130.9 (C), 135.1 (CH),
135.7, 136.5, 137.7, 140.3, 141.5, 148.8, 149.2 (C), 190.3
(CO). IR (KBr): 3076, 3012, 2966, 2939, 2919, 2838, 2249
(w), 1718 (s), 1623, 1600, 1579 (w), 1517, 1511 (m), 1468,
1448 (w), 1404 (s), 1374, 1345, 1334, 1319, 1297, 1255 (w),
1215 (s), 1172 (m), 1134 (s), 1090, 1054 (w), 1020 (m), 998
(s), 963 (m), 913 (w), 892 (m), 866 (w), 817, 804 (s), 788,
777 (w), 758 (s), 745 (w), 722 (s), 687 (m), 665 (w), 653, 647
(m), 629, 611 (s), 589, 559 (w) cm–1. GC–MS (EI, 70 eV):
m/z (%) = 514 (28) [M+], 381 (100), 353 (4). HRMS (EI, 70
eV): m/z calcd for C26H17O6F3S: 514.06925; found:
514.070130.
(20) General Procedure for Suzuki–Miyaura Reactions: A
1,4-dioxane solution (4–5 mL/0.3 mmol of 2) of K3PO4
(1.5–2.0 equiv), Pd(PPh3)4 (3 mol% per cross-coupling) and
arylboronic acid 3 (1.0–1.1 equiv per cross-coupling) was
stirred at 60–90 °C for 10 h. After cooling to 20 °C, distilled
H2O was added. The organic and the aqueous layers were
separated and the latter was extracted with CH2Cl2. The
combined organic layers were dried (Na2SO4), filtered and
the filtrate was concentrated in vacuo. The residue was
purified by column chromatography.
(23) Synthesis of 5-(3,5-Dimethylphenyl)-10-(4-
methoxyphenyl)-11H-benzo[b]fluoren-11-one (6a):
Starting with 2 (150 mg, 0.28 mmol), 4-methoxy-
(21) Synthesis of 5,10-Bis(4-methoxyphenyl)-11H-benzo[b]-
fluoren-11-one (4a): Starting with 2 (150 mg, 0.28 mmol),
4-methoxyphenylboronic acid (3a; 96 mg, 0.63 mmol),
Pd(PPh3)4 (19 mg, 6 mol%), K3PO4 (178 mg, 0.84 mmol)
and 1,4-dioxane (5 mL), 4a was isolated as a yellow solid
(100 mg, 80%); mp 243–245 °C. 1H NMR (300 MHz,
CDCl3): d = 3.85 (s, 3 H, OMe), 3.90 (s, 3 H, OMe), 6.31–
6.36 (m, 1 H, ArH), 7.02 (d, 2 H, J = 8.4 Hz, ArH), 7.07–7.12
(m, 4 H, ArH), 7.25–7.31 (m, 5 H, ArH), 7.35 (td, 1 H, J =
1.4, 8.1 Hz, ArH), 7.43–7.46 (m, 1 H, ArH), 7.50–7.58 (m, 1
H, ArH), 7.63–7.66 (m, 1 H, ArH). 13C NMR (75.5 MHz,
CDCl3): d = 55.3, 55.4 (OMe), 113.6, 114.8, 123.8, 123.9,
126.5, 127.1 (CH), 127.8, 128.4 (C), 128.5, 129.0 (CH),
129.8 (C), 130.9, 131.0 (CH), 133.9, 134.0 (C), 134.3 (CH),
135.8, 136.8, 137.2, 140.5, 144.5, 159.4, 159.6 (C), 192.6
(CO). IR (KBr): 3064, 2997, 2952, 2929, 2849, 2831 (w),
1704 (s), 1606, 1589 (m), 1579 (w), 1510 (s), 1462, 1441,
1410, 1361, 1335, 1311 (w), 1286 (m), 1243 (s), 1215, 1191
(m), 1173 (s), 1107, 1086, 1048 (w), 1034, 1026 (m), 1005
(w), 963 (m), 932, 899 (w), 870, 830, 805, 791 (m), 759, 727
(s), 693, 681, 655, 633 (w), 623, 596 (m), 573 (w), 559, 531
(m) cm–1. GC–MS (EI, 70 eV): m/z (%) = 442 (100) [M+],
441 (28), 411 (6), 326 (5). HRMS (EI, 70 eV): m/z calcd for
C31H22O3: 442.15635; found: 442.155487.
phenylboronic acid (3a; 43 mg, 0.28 mmol), Pd(PPh3)4 (10
mg, 3 mol%), K3PO4 (119 mg, 0.56 mmol), 1,4-dioxane (5
mL), and 3,5-dimethylphenylboronic acid (3d; 46 mg, 0.31
mmol), 6a was isolated as a yellow solid (90 mg, 72%); mp
220–222 °C. 1H NMR (300 MHz, CDCl3): d = 2.36 (s, 6 H,
2 × Me), 3.85 (s, 3 H, OMe), 6.27–6.33 (m, 1 H, ArH), 6.98
(br s, 2 H, ArH), 7.02 (d, 2 H, J = 8.8 Hz, ArH), 7.08–7.14
(m, 3 H, ArH), 7.26 (d, 2 H, J = 8.8 Hz, ArH), 7.27–7.30 (m,
1 H, ArH), 7.34 (td, 1 H, J = 1.3, 8.2 Hz, ArH), 7.43–7.46
(m, 1 H, ArH), 7.50–7.53 (m, 1 H, ArH), 7.63–7.66 (m, 1 H,
ArH). 13C NMR (75.5 MHz, CDCl3): d = 21.5 (2 × Me), 55.3
(OMe), 113.6, 123.8, 123.9, 126.5, 127.3, 127.4 (CH),
127.8, 128.4 (C), 128.5, 128.9, 129.8, 131.0 (CH), 134.0 (C),
134.4 (CH), 134.5, 135.2, 136.7, 136.8, 137.6, 139.9, 140.4,
144.5, 159.4 (C), 192.6 (CO). IR (KBr): 3068, 3000, 2955,
2923, 2852 (w), 1703, 1695, 1598, 1505 (s), 1466, 1435,
1423, 1363, 1336, 1311, 1302, 1287, 1259 (w), 1244 (s),
1202 (m), 1172 (s), 1130, 1105, 1087, 1049 (w), 1029, 998
(m), 969, 950, 939, 926, 906 (w), 873 (m), 848, 834 (w), 826,
790, 778 (m), 761 (s), 742 (w), 724 (s), 710, 703, 680, 661,
631 (w), 613, 595 (m), 579 (w), 562, 538 (m) cm–1. GC–MS
(EI, 70 eV): m/z (%) = 440 (100) [M+], 409 (6), 396 (4).
HRMS (ESI+): m/z [M + H]+ calcd for C32H24O2: 440.17708;
found: 440.176873.
(22) Synthesis of 10-(3,4-Dimethoxyphenyl)-11-oxo-11H-
benzo[b]fluoren-5-yl Trifluoromethanesulfonate (5g):
Starting with 2 (150 mg, 0.28 mmol), 3,4-dimethoxy-
phenylboronic acid (3g; 56 mg, 0.3 mmol), Pd(PPh3)4 (10
mg, 3 mol%), K3PO4 (119 mg, 0.56 mmol) and 1,4-dioxane
(5 mL), 5g was isolated as a yellow solid (129 mg, 88%); mp
221–222 °C. 1H NMR (300 MHz, CDCl3): d = 3.79 (s, 3 H,
OMe), 3.92 (s, 3 H, OMe), 6.79–6.85 (m, 2 H, ArH), 6.97 (d,
1 H, J = 8.2 Hz, ArH), 7.33 (td, 1 H, J = 0.8, 7.4 Hz, ArH),
7.39–7.44 (m, 1 H, ArH), 7.53–7.68 (m, 4 H, ArH), 8.02 (d,
2 H, J = 7.8 Hz, ArH). 19F NMR (282.4 MHz, CDCl3): d =
(24) CCDC 799371 contains all crystallographic details
of this publication and is available free of charge at
www.ccdc.cam.ac.uk/conts/retrieving.html or can be
ordered from the following address: Cambridge
Crystallographic Data Centre, 12 Union Road, GB-
Cambridge CB21EZ, U.K.; Fax: +44 (1223)336033; or
Email: deposit@ccdc.cam.ac.uk.
(25) For a simple guide for the prediction of the site-selectivity of
palladium(0)-catalyzed cross-coupling reactions based on
the 1H NMR chemical shift values, see: Handy, S. T.; Zhang,
Y. Chem. Commun. 2006, 299.
Synlett 2010, No. 20, 3031–3034 © Thieme Stuttgart · New York

Copyright of Synlett is the property of Georg Thieme Verlag Stuttgart and its content may not
be copied or emailed to multiple sites or posted to a listserv without the copyright holder's
express written permission. However, users may print, download, or email articles for
individual use.