Palladium-catalyzed C-H bond functionalization/oxidative acyloxylation of 2-aryl-benzo[d]thiazoles

Article abstract of DOI:10.1016/j.jorganchem.2013.04.026

A chelation-assisted Pd-catalyzed ortho-acyloxylation reaction of the 2-arylbenzo[d]thiazole is described via sp² C-H bond activation. A wide substrate scope with good functional group tolerance has been demonstrated, affording mono- or diacyloxylation products in moderate to good yields. This method is an alternative route for the preparation of 2-arylbenzo[d]thiazole derivatives via a C-H activation mechanism.

Full text of DOI:10.1016/j.jorganchem.2013.04.026

Journal of Organometallic Chemistry 739 (2013) 33e39
Contents lists available at SciVerse ScienceDirect
Journal of Organometallic Chemistry
journal homepage: www.elsevier.com/locate/jorganchem
Palladium-catalyzed CeH bond functionalization/oxidative
acyloxylation of 2-aryl-benzo[d]thiazoles
*
*
Qiuping Ding , Huafang Ji, Ziyi Nie, Qin Yang, Yiyuan Peng
Key Laboratory of Functional Small Organic Molecules, Ministry of Education and College of Chemistry & Chemical Engineering,
Jiangxi Normal University, Nanchang, Jiangxi 330022, China
a r t i c l e i n f o
a b s t r a c t
Article history:
A chelation-assisted Pd-catalyzed ortho-acyloxylation reaction of the 2-arylbenzo[d]thiazole is described
via sp2 CeH bond activation. A wide substrate scope with good functional group tolerance has been
demonstrated, affording mono- or diacyloxylation products in moderate to good yields. This method is an
Received 9 January 2013
Received in revised form
4 April 2013
alternative route for the preparation of 2-arylbenzo[d]thiazole derivatives via
a CeH activation
Accepted 10 April 2013
mechanism.
Ó 2013 Elsevier B.V. All rights reserved.
Keywords:
Arylbenzothiazole
CeH activation
Acyloxylation
1. Introduction
[14], pyrazole [14,32], imine [14], pyridine [14,27,29,33e35], 2-
pyrimidyldiisopropylsilyl (PyrDipSi) [31] oxime ether [23,24,36],
Boc-protected N-methylamine [25], anilide [26], sulfoximine [30],
and benzoxazole [36]. For example, Sanford reported the elegant
work of Pd-catalyzed chelate-directed oxidative acetoxylation of
sp2 and sp3 CeH bonds [14]. Yu developed the pyridyl group-
directed Cu(OAc)2-catalyzed oxidative acyloxylation of arene CeH
bonds in HOAc/Ac2O using oxygen as terminal oxidant [17].
Benzothiazole is a common structural motif in many natural
products and pharmaceuticals that exhibit remarkable antitumor
activities [38e41]. Therefore, many efforts have been given for the
development of new approaches for the construction of benzo-
thiazole derivatives. Recently, we developed an efficient method for
the arylation of 2-arylbenzothiazoles via CeH activation [42]. Our
interest in heterocycle [43e46] and CeH functionalization [42,47]
led us to explore the possibility of acyloxylation using 2-aryl-
benzo[d]thiazole as the reaction substrate. Herein, we report a Pd-
catalyzed oxidative acyloxylation of arene CeH bonds using benzo
[d]thiazole as directing group.
The developing of transition metal-catalyzed carbonehydrogen
(CeH) bond activation is a big leap in knowledge of how to cleave
and functionalize inert CeH bonds effectively. During the past
several decades, great progress has been made in the direct for-
mation of carbonecarbon [1e7] and carboneheteroatom (CeN [8e
10], CeS [11e13], CeX [14e22], and CeO [14,23e37]) bonds from
both of unactivated sp2 and sp3 CeH bonds via CeH activation.
However, these transformations suffer from two fundamental
challenges: (i) reactivity of unactivated CeH bonds and (ii) regio-
selectivity. Much endeavor for the challenges has been done from
three aspects. The first effective measure is choosing transition
metals (Pd, Ru, Rh, and Cu) to make CeH bonds activation and in-
crease the rates of reactions. A second method is the use of a variety
of different oxidants [such as iodine(III) oxidant, iodine(I) oxidant,
peroxide oxidant, and dioxygen] to effect the transformation via
producing high oxidation state metal intermediate which was
involved in mechanism. The third one is the use of substrates with
directing group which can coordinate with transition metal center
via favorable five- or six-membered transition states. Among these,
significant progress has been made in directing-group-assisted
transition metal-catalyzed CeH acetoxylation. The substrates con-
taining directing-group include benzoquinoline [14], azobenzene
2. Experimental
2.1. General remarks
All reactions were performed in reaction tubes under nitrogen
atmosphere. Flash column chromatography was performed using
ꢀ
silica gel (60-A pore size, 32e63
m
m, standard grade). Analytical
* Corresponding authors. Tel./fax: þ86 791 88120380.
E-mail addresses: dqpjxnu@gmail.com (Q. Ding), yiyuanpeng@yahoo.com
(Y. Peng).
thin-layer chromatography was performed using glass plates pre-
coated with 0.25 mm 230e400 mesh silica gel impregnated with
0022-328X/$ e see front matter Ó 2013 Elsevier B.V. All rights reserved.
http://dx.doi.org/10.1016/j.jorganchem.2013.04.026

34
Q. Ding et al. / Journal of Organometallic Chemistry 739 (2013) 33e39
a fluorescent indicator (254 nm). Thin layer chromatography plates
were visualized by exposure to ultraviolet light. Organic solutions
were concentrated on rotary evaporators at w20 Torr (house vac-
uum) at 25e35 ꢀC. Commercial reagents and solvents were used as
received. 1H NMR (400 MHz) and 13C NMR (100 MHz) spectra were
recorded in CDCl3 using a Bruker Avance (AV400) spectrometer in
2.2.6. 2-(6-Fluorobenzo[d]thiazol-2-yl)-3-methylphenyl acetate 3fa
1H NMR (400 MHz, CDCl3)
2.07 (s, 3H), 2.35 (s, 3H), 7.06 (d,
d
J ¼ 8.0 Hz, 1H), 7.21e7.29 (m, 2H), 7.41 (t, J ¼ 8.0 Hz, 1H), 7.61
(dd, J ¼ 2.4, 8.0 Hz, 1H), 8.06 (dd, J ¼ 4.8, 9.2 Hz, 1H); 13C NMR
2
(100 MHz, CDCl3)
d
20.3, 20.8, 107.6 (d, JCeF ¼ 26.0 Hz), 114.9
2
3
(d, JCeF ¼ 25.0 Hz), 120.5, 124.6 (d, JCeF ¼ 10.0 Hz), 126.5,
3
parts per million from internal tetramethylsilane on the
d
scale.
128.3, 130.7, 137.1 (d, JCeF ¼ 11.0 Hz), 139.6, 149.1, 149.8, 159.4
1
4
HRMS were obtained using a Nova NanoSEM 200 (FEI) instrument
with ESI ionization.
(d, JCeF ¼ 245.0 Hz), 162.4 (d, JCeF ¼ 4.0 Hz), 169.3; HRMS
(ESI): m/z [M þ H]þ calcd for C16H13FNO2S: 302.0651; found:
302.0651.
2.2. General procedure for CeH bond activation/acyloxylation of 2-
arylbenzothiazoles 1 with iodine(III) oxidants 2
2.2.7. 2-(Benzo[d]thiazol-2-yl)-3-fluorophenyl acetate 3ga
1H NMR (400 MHz, CDCl3)
d
2.31 (s, 3H), 7.07 (d, J ¼ 8.0 Hz, 1H),
In a 20 mL reaction tube, a mixture of 2-arylbenzothiazole 1
(0.3 mmol, 1.0 equiv), iodine(III) oxidants 2 (0.9 mmol, 3.0 equiv),
and Pd(OAc)2 (5 mol %) in dried CH3CN (1.0 mL) was stirred at 90 ꢀC
for 6e12 h. After completion of the reaction as indicated by TLC, the
mixture was cooled to room temperature, the resulting mixture
was extracted with ethyl acetate (3 ꢁ 20 mL). The organic layer was
evaporated under vacuum, and then the residue was purified by
flash column chromatography on silica gel to provide the corre-
sponding pure product 3 and (or) 4.
7.17 (t, J ¼ 8.8 Hz,1H), 7.41e7.53 (m, 3H), 7.94 (d, J ¼ 8.0 Hz,1H), 8.10
(d, J ¼ 8.0 Hz, 1H); 13C NMR (100 MHz, CDCl3)
d
21.2, 114.1 (d, 2JCe
3
¼ 22.0 Hz), 116.1 (d, JCeF ¼ 14.0 Hz), 119.8, 121.4, 123.4, 125.7,
F
3
126.3, 131.5 (d, JCeF ¼ 10.0 Hz), 135.6, 149.5, 152.8, 157.2, 160.8 (d,
1JCeF ¼ 252.0 Hz), 169.4; HRMS (ESI): m/z [M þ H]þ calcd for
C15H11FNO2S: 288.0495; found: 288.0499.
2.2.8. 3-Fluoro-2-(6-methylbenzo[d]thiazol-2-yl)phenyl acetate 3ha
1H NMR (400 MHz, CDCl3)
d 2.29 (s, 3H), 2.50 (s, 3H), 7.05 (d,
J ¼ 8.0 Hz, 1H), 7.14 (t, J ¼ 9.2 Hz, 1H), 7.31 (d, J ¼ 8.0 Hz, 1H), 7.44 (d,
2.2.1. 2-(Benzo[d]thiazol-2-yl)-1,3-phenylene diacetate 4aa
J ¼ 6.8 Hz, 1H), 7.72 (s, 1H), 7.97 (d, J ¼ 8.0 Hz, 1H); 13C NMR
1H NMR (400 MHz, CDCl3)
d
2.24 (s, 6H), 7.16 (d, J ¼ 8.0 Hz, 2H),
(100 MHz, CDCl3)
d
21.2, 21.6, 114.0 (d, 2JCeF ¼ 23.0 Hz), 116.3 (d, 3JCe
3
7.43 (d, J ¼ 7.6 Hz, 1H), 7.48e7.52 (m, 2H), 7.93 (d, J ¼ 8.0 Hz, 1H),
¼ 14.0 Hz), 119.8, 121.0, 123.0, 127.9, 131.3 (d, JCeF ¼ 10.0 Hz),
F
8.09 (d, J ¼ 8.0 Hz, 1H); 13C NMR (100 MHz, CDCl3)
d
21.2, 120.7,
135.8, 135.9, 149.5, 150.9, 156.0, 160.8 (d, 1JCeF ¼ 252.0 Hz), 169.4;
HRMS (ESI): m/z [M þ H]þ calcd for C16H13FNO2S: 302.0651; found:
302.0651.
121.3, 121.4, 123.5, 125.7, 126.3, 131.0, 135.6, 149.4, 152.8, 158.4,
169.0; HRMS (ESI): m/z [M þ H]þ calcd for C17H14NO4S: 328.0644;
found: 328.0640.
2.2.9. 2-(6-Chlorobenzo[d]thiazol-2-yl)-3-fluorophenyl acetate 3ia
2.2.2. 2-(6-Methylbenzo[d]thiazol-2-yl)-1,3-phenylene diacetate 4ba
1H NMR (400 MHz, CDCl3)
d
2.32 (s, 3H), 7.07 (d, J ¼ 8.0 Hz, 1H),
1H NMR (400 MHz, CDCl3)
d
2.23 (s, 6H), 2.50 (s, 3H), 7.15 (d,
7.18 (t, J ¼ 8.8 Hz, 1H), 7.46e7.50 (m, 2H), 7.92 (s, 1H), 7.99 (d,
2
J ¼ 8.4 Hz, 2H), 7.31 (d, J ¼ 8.4 Hz, 1H), 7.48 (t, J ¼ 8.0 Hz, 1H), 7.72 (s,
J ¼ 8.4 Hz, 1H); 13C NMR (100 MHz, CDCl3)
d 21.2, 114.1 (d, JCe
1H), 7.96 (J ¼ 8.4 Hz, 1H); 13C NMR (100 MHz, CDCl3)
d
21.1, 21.6,
¼ 23.0 Hz), 115.7 (d, JCeF ¼ 14.0 Hz), 119.9, 121.0, 124.3, 127.2,
3
F
1
120.8, 121.0, 121.2, 123.0, 127.9, 130.8, 135.9, 149.4, 151.0, 157.3,
168.9; HRMS (ESI): m/z [M þ H]þ calcd for C18H16NO4S: 342.0800;
found: 342.0808.
131.7, 131.8, 136.7, 149.4, 151.2, 157.7, 160.8 (d, JCeF ¼ 253.0 Hz),
169.3; HRMS (ESI): m/z [M þ K]þ calcd for C15H9ClFKNO2S:
359.9664; found: 359.9646.
2.2.3. 2-(Benzo[d]thiazol-2-yl)-3-methylphenyl acetate 3ca
2.2.10. 3-Fluoro-2-(6-fluorobenzo[d]thiazol-2-yl)phenyl acetate 3ja
1H NMR (400 MHz, CDCl3)
d
2.06 (s, 3H), 2.34 (s, 3H), 7.05 (d,
1H NMR (400 MHz, CDCl3)
d
2.32 (s, 3H), 7.07 (d, J ¼ 8.4 Hz, 1H),
J ¼ 8.4 Hz, 1H), 7.22 (d, J ¼ 7.6 Hz, 1H), 7.38e7.46 (m, 2H), 7.70e
7.17 (t, J ¼ 9.2 Hz, 1H), 7.25 (t, J ¼ 8.8 Hz, 1H), 7.48 (t, J ¼ 6.8 Hz, 1H),
7.55 (m, 1H), 7.94 (d, J ¼ 8.0 Hz, 1H), 8.13 (d, J ¼ 8.0 Hz, 1H); 13C
7.62 (d, J ¼ 8.0 Hz, 1H), 8.03 (q, J ¼ 4.4 Hz, 1H); 13C NMR (100 MHz,
2
2
NMR (100 MHz, CDCl3)
d
20.3, 20.9, 120.5, 121.5, 123.6, 125.4, 126.1,
CDCl3)
d
21.1, 107.5 (d, JCeF ¼ 26.0 Hz), 114.1 (d, JCeF ¼ 22.0 Hz),
126.9, 128.2, 130.6, 136.1, 139.7, 149.1, 153.2, 162.8, 169.4; HRMS
(ESI): m/z [M þ H]þ calcd for C16H14NO2S: 284.0745; found:
284.0740.
115.1 (d, 2JCeF ¼ 24.0 Hz), 115.8 (d, 2JCeF ¼ 25.0 Hz), 119.9, 124.5 (d,
3JCeF ¼ 9.0 Hz), 131.6 (d, JCeF ¼ 11.0 Hz), 136.6, 136.7, 149.4, 156.9,
3
160.7 (d, 1JCeF ¼ 245.0 Hz), 160.8 (d, 1JCeF ¼ 253.0 Hz), 169.3; HRMS
(ESI): m/z [M þ H]þ calcd for C15H10F2NO2S: 306.0400; found:
306.0389.
2.2.4. 3-Methyl-2-(6-methylbenzo[d]thiazol-2-yl)phenyl acetate 3da
1H NMR (400 MHz, CDCl3)
d 2.05 (s, 3H), 2.33 (s, 3H), 2.52 (s, 3H),
7.04 (d, J ¼ 8.4 Hz,1H), 7.20 (d, J ¼ 7.6 Hz,1H), 7.33 (d, J ¼ 8.4 Hz,1H),
2.2.11. 2-(Benzo[d]thiazol-2-yl)-3-chlorophenyl acetate 3ka
7.38 (t, J ¼ 8.0 Hz, 1H), 7.72 (s, 1H), 8.01 (d, J ¼ 8.0 Hz, 1H); 13C NMR
1H NMR (400 MHz, CDCl3)
d
2.05 (s, 3H), 7.18 (q, J ¼ 3.2 Hz, 1H),
(100 MHz, CDCl3)
d
20.3, 20.8, 21.6, 120.4, 121.2, 123.1, 126.9, 127.7,
7.44e7.48 (m, 3H), 7.54 (t, J ¼ 7.2 Hz, 1H), 7.96 (d, J ¼ 8.0 Hz, 1H),
128.2, 130.5, 131.8, 135.6, 136.3, 139.7, 149.1, 151.3, 161.7, 169.4;
HRMS (ESI): m/z [M þ H]þ calcd for C17H16NO2S: 298.0902; found:
298.0906.
8.16 (d, J ¼ 8.0 Hz, 1H); 13C NMR (100 MHz, CDCl3)
d 20.7, 121.6,
122.0, 123.8, 125.7, 126.3, 126.9127.7, 131.3, 134.9, 136.2, 150.0, 152.9,
160.2, 169.0; HRMS (ESI): m/z [M þ K]þ calcd for C15H10ClKNO2S:
341.9758; found: 341.9745.
2.2.5. 2-(6-Chlorobenzo[d]thiazol-2-yl)-3-methylphenyl acetate 3ea
1H NMR (400 MHz, CDCl3)
d
2.06 (s, 3H), 2.34 (s, 3H), 7.06 (d,
2.2.12. 3-Chloro-2-(6-methylbenzo[d]thiazol-2-yl)phenyl acetate 3la
J ¼ 8.0 Hz, 1H), 7.22 (d, J ¼ 8.0 Hz, 1H), 7.40 (t, J ¼ 8.0 Hz, 1H), 7.49
1H NMR (400 MHz, CDCl3)
d 2.05 (s, 3H), 2.52 (s, 3H), 7.15e7.18
(dd, J ¼ 2.0, 4.8 Hz, 1H), 7.91 (d, J ¼ 2.0 Hz, 1H), 8.02 (d, J ¼ 8.8 Hz,
(m, 1H), 7.35 (d, J ¼ 8.0 Hz, 1H), 7.42e7.45 (m, 2H), 7.74 (s, 1H), 8.03
1H); 13C NMR (100 MHz, CDCl3)
d
20.3, 20.8, 120.5, 121.1, 124.3,
(d, J ¼ 8.0 Hz, 1H); 13C NMR (100 MHz, CDCl3)
d 20.7, 21.6, 121.3,
126.4, 127.0, 128.3, 130.8, 131.4, 137.3, 139.6, 149.0, 151.7, 163.3,
169.2; HRMS (ESI): m/z [M þ H]þ calcd for C16H13ClNO2S: 318.0356;
found: 318.0350.
121.9, 123.3, 127.0, 127.7, 127.9, 131.2, 134.9, 136.0, 136.5, 150.1, 151.1,
159.1, 169.0; HRMS (ESI): m/z [M þ H]þ calcd for C16H13ClNO2S:
318.0356; found: 318.0349.

Q. Ding et al. / Journal of Organometallic Chemistry 739 (2013) 33e39
35
2.2.13. 3-Chloro-2-(6-chlorobenzo[d]thiazol-2-yl)phenyl acetate 3ma
2.2.19. 2-(6-Chlorobenzo[d]thiazol-2-yl)-4-methylphenyl acetate 3sa
1H NMR (400 MHz, CDCl3)
d
2.06 (s, 3H), 7.18 (d, J ¼ 7.2 Hz
1H NMR (400 MHz, CDCl3)
d
2.42 (s, 3H), 2.44 (s, 3H), 7.11 (d,
1H), 7.43e7.51 (m, 3H), 7.93 (s, 1H), 8.06 (d, J ¼ 8.8 Hz, 1H); 13C
J ¼ 8.0 Hz, 1H), 7.29 (d, J ¼ 8.0 Hz, 1H), 7.43 (d, J ¼ 8.0 Hz, 1H), 7.86
NMR (100 MHz, CDCl3)
d 20.7, 121.2, 122.0, 124.6, 126.4, 127.2,
(d, J ¼ 2.0 Hz, 1H), 7.95 (d, J ¼ 8.8 Hz, 1H), 8.09 (s, 1H); 13C NMR
127.8, 131.6, 131.8, 134.8, 137.4, 150.0, 151.5, 160.7, 168.9; HRMS
(ESI): m/z [M þ K]þ calcd for C15H9Cl2KNO2S: 375.9368; found:
375.9362.
(100 MHz, CDCl3) d 20.9, 21.7, 120.9, 123.5, 124.0, 125.2, 127.2, 130.3,
131.2, 132.5, 136.4, 136.6, 146.1, 151.4, 163.1, 169.2; HRMS (ESI): m/z
[M þ H]þ calcd for C16H13ClNO2S: 318.0356; found: 318.0350.
2-(6-chlorobenzo[d]thiazol-2-yl)-4-methyl-1,3-phenylene
diac-
2.2.14. 3-Chloro-2-(6-fluorobenzo[d]thiazol-2-yl)phenyl acetate 3na
etate 4sa. 1H NMR (400 MHz, CDCl3)
d 2.14 (s, 3H), 2.16 (s, 3H), 2.17
1H NMR (400 MHz, CDCl3)
d
2.06 (s, 3H), 7.17 (d, J ¼ 6.8 Hz, 1H),
(s, 3H), 7.01 (d, J ¼ 8.4 Hz, 1H), 7.31 (d, J ¼ 8.4 Hz, 1H), 7.39 (dd,
7.27 (t, J ¼ 8.0 Hz, 1H), 7.42e7.47 (m, 2H), 7.63 (d, J ¼ 7.2 Hz, 1H),
J ¼ 1.6, 8.4 Hz,1H), 7.83 (d, J ¼ 1.6 Hz,1H), 7.91 (d, J ¼ 8.4 Hz,1H); 13C
8.09 (q, J ¼ 4.0 Hz, 1H); 13C NMR (100 MHz, CDCl3)
d
20.7, 107.7 (d,
NMR (100 MHz, CDCl3) d 16.6, 21.1, 21.4, 120.7, 121.3, 124.6, 127.4,
2
3
2JCeF ¼ 16.0 Hz), 115.1 (d, JCeF ¼ 24.0 Hz), 122.0, 124.8 (d, JCe
130.1, 132.0, 133.1, 133.2, 137.3, 147.7, 148.2, 151.8, 159.8, 168.6, 169.2;
HRMS (ESI): m/z [M þ H]þ calcd for C18H15ClNO4S: 376.0410; found:
376.0401.
3
¼ 10.0 Hz), 126.5, 127.8, 131.5, 134.8, 137.3 (d, JCeF ¼ 12.0 Hz),
F
149.6, 150.0, 159.9, 160.8 (d, 1JCeF ¼ 246.0 Hz), 168.9; HRMS (ESI):
m/z [M
359.9649.
þ
K]þ calcd for C15H9ClFKNO2S: 359.9664; found:
2.2.20. 2-(6-Fluorobenzo[d]thiazol-2-yl)-4-methylphenyl acetate 3ta
1H NMR (400 MHz, CDCl3)
d 2.42 (s, 3H), 2.44 (s, 3H), 7.11 (d,
2.2.15. 2-(Benzo[d]thiazol-2-yl)-4-chlorophenyl acetate 3oa
1H NMR (400 MHz, CDCl3)
J ¼ 8.4 Hz, 1H), 7.22 (dt, J ¼ 2.8, 8.8 Hz, 1H), 7.28 (dd, J ¼ 1.6, 8.4 Hz,
d
2.46 (s, 3H), 7.18 (d, J ¼ 8.8 Hz, 1H),
1H), 7.57 (dd, J ¼ 2.4, 8.0 Hz, 1H), 8.00 (dd, J ¼ 4.8, 8.8 Hz, 1H), 8.07
7.38e7.44 (m, 2H), 7.50 (d, J ¼ 7.6 Hz, 1H), 7.91 (d, J ¼ 8.0 Hz, 1H),
(d, J ¼ 1.6 Hz, 1H); 13C NMR (100 MHz, CDCl3)
d 20.9, 21.7, 107.3 (d,
8.08 (d, J ¼ 8.0 Hz, 1H), 8.35 (d, J ¼ 2.4 Hz, 1H); 13C NMR (100 MHz,
2JCeF ¼ 26.0 Hz), 114.9 (d, JCeF ¼ 24.0 Hz), 123.4, 124.2 (d, JCe
2
3
CDCl3)
d
21.7, 121.4, 123.6, 125.1, 125.7, 126.6, 127.5, 129.7, 131.1,
¼ 9.0 Hz), 125.3, 130.2, 132.3, 136.3, 136.5, 146.1, 149.6, 160.5 (d,
F
132.0, 135.5, 146.7, 152.7, 160.8, 168.8; HRMS (ESI): m/z [M þ H]þ
1JCeF ¼ 244.0 Hz), 162.4 (d, 4JCeF ¼ 3.0 Hz), 169.2; HRMS (ESI): m/z
calcd for C15H11ClNO2S: 304.0199; found: 304.0197.
[M þ H]þ calcd for C16H13FNO2S: 302.0651; found: 302.0651.
2.2.16. 4-Chloro-2-(6-chlorobenzo[d]thiazol-2-yl)phenyl acetate 3pa
2.2.21. 2-(Benzo[d]thiazol-2-yl)-3-methylphenyl pivalate 3cb
1H NMR (400 MHz, CDCl3)
d
2.46 (s, 3H), 7.18 (d, J ¼ 8.4 Hz, 1H),
1H NMR (400 MHz, CDCl3)
d 1.00 (s, 9H), 2.29 (s, 3H), 7.02 (d,
7.42e7.46 (m, 2H), 7.86 (d, J ¼ 1.6 Hz, 1H), 7.96 (d, J ¼ 8.8 Hz, 1H),
J ¼ 8.0 Hz,1H), 7.19 (d, J ¼ 7.6 Hz,1H), 7.39 (d, J ¼ 8.0 Hz,1H), 7.43 (d,
8.31 (d, J ¼ 2.0 Hz, 1H); 13C NMR (100 MHz, CDCl3)
d 21.7, 121.0,
J ¼ 8.0 Hz, 1H), 7.51 (t, J ¼ 8.0 Hz, 1H), 7.92 (d, J ¼ 8.0 Hz, 1H), 8.11 (d,
124.3, 125.0, 126.9, 127.4, 129.6, 131.4, 131.7, 132.1, 136.6, 146.7, 151.1,
161.1, 168.6; HRMS (ESI): m/z [M þ H]þ calcd for C15H10Cl2NO2S:
337.9809; found: 337.9812.
J ¼ 8.4 Hz, 1H); 13C NMR (100 MHz, CDCl3)
d 19.9, 26.8, 38.9, 120.2,
121.4, 123.5, 125.3, 126.1, 127.1, 127.7, 130.5, 136.1, 139.4, 149.5, 153.2,
162.9, 176.6; HRMS (ESI): m/z [M þ H]þ calcd for C19H20NO2S:
326.1215; found: 326.1210.
2.2.17. 2-(Benzo[d]thiazol-2-yl)-4-methylphenyl acetate 3qa
1H NMR (400 MHz, CDCl3)
d
2.43 (s, 3H), 2.44 (s, 3H), 7.11 (d,
2.2.22. 2-(6-Fluorobenzo[d]thiazol-2-yl)-3-methylphenyl pivalate 3fb
J ¼ 8.8 Hz, 1H), 7.29 (d, J ¼ 8.4 Hz, 1H), 7.38 (t, J ¼ 8.0 Hz, 1H), 7.49 (t,
1H NMR (400 MHz, CDCl3)
d 1.01 (s, 9H), 2.29 (s, 3H), 7.02 (d,
J ¼ 7.6 Hz,1H), 7.90 (d, J ¼ 8.0 Hz,1H), 8.08 (d, J ¼ 8.0 Hz,1H), 8.12 (s,
J ¼ 8.0 Hz, 1H), 7.19 (d, J ¼ 7.6 Hz, 1H), 7.24 (dt, J ¼ 2.4, 8.0 Hz, 1H),
1H); 13C NMR (100 MHz, CDCl3)
d 20.9, 21.7, 121.3, 123.3, 123.5,
7.40 (t, J ¼ 8.0 Hz, 1H), 7.60 (dd, J ¼ 2.4, 8.0 Hz, 2H), 8.06 (dd, J ¼ 4.4,
125.3, 125.6, 126.3, 130.4, 132.2, 135.4, 136.3, 146.2, 152.9, 162.7,
169.3; HRMS (ESI): m/z [M þ H]þ calcd for C16H14NO2S: 284.0745;
found: 284.0741.
8.8 Hz, 1H); 13C NMR (100 MHz, CDCl3)
d
19.9, 26.7, 38.9, 107.6 (d,
2
3
2JCeF ¼ 27.0 Hz), 114.9 (d, JCeF ¼ 25.0 Hz), 120.3, 124.4 (d, JCe
¼ 9.0 Hz), 126.7, 127.7, 130.7, 137.0 (d, 3JCeF ¼ 9.0 Hz), 139.3, 149.4,
F
3
2-(benzo[d]thiazol-2-yl)-4-methyl-1,3-phenylene diacetate 4qa.
149.8, 160.5 (d, 1JCeF ¼ 245.0 Hz), 162.7 (d, JCeF ¼ 4.0 Hz), 176.6;
1H NMR (400 MHz, CDCl3)
d
2.22 (s, 3H), 2.23 (s, 3H), 2.25 (s, 3H),
HRMS (ESI): m/z [M þ H]þ calcd for C19H19FNO2S: 344.1121; found:
7.08 (d, J ¼ 8.0 Hz,1H), 7.38 (d, J ¼ 8.0 Hz,1H), 7.43 (t, J ¼ 8.0 Hz,1H),
344.1125.
7.51 (t, J ¼ 8.0 Hz,1H), 7.93 (d, J ¼ 7.6 Hz,1H), 8.09 (d, J ¼ 8.0 Hz,1H);
13C NMR (100 MHz, CDCl3)
d
20.8, 21.1, 22.7, 120.7, 120.9, 121.4,
2.2.23. 4-Methyl-2-(6-methylbenzo[d]thiazol-2-yl)phenyl pivalate 3rb
123.5, 125.5, 126.2, 129.7, 132.6, 135.7, 147.4, 147.9, 152.9, 158.9,
168.5, 169.0; HRMS (ESI): m/z [M þ H]þ calcd for C18H16NO4S:
342.0800; found: 342.0804.
1H NMR (400 MHz, CDCl3)
d 1.40 (s, 9H), 2.41 (s, 3H), 2.47 (s, 3H),
6.99 (d, J ¼ 8.0 Hz, 1H), 7.25 (d, J ¼ 8.4 Hz, 1H), 7.27 (d, J ¼ 8.4 Hz,
1H), 7.68 (s, 1H), 7.93 (s, 1H), 7.94 (d, J ¼ 8.4 Hz, 1H); 13C NMR
(100 MHz, CDCl3)
d 20.8, 21.6, 27.3, 39.2, 121.1, 122.8, 123.3, 126.3,
2.2.18. 4-Methyl-2-(6-methylbenzo[d]thiazol-2-yl)phenyl acetate 3ra
127.9, 130.8, 131.9, 135.4,135.7,135.9, 146.7,151.4, 162.1,177.1; HRMS
(ESI): m/z [M þ H]þ calcd for C20H22NO2S: 340.1371; found:
340.1376.
1H NMR (400 MHz, CDCl3)
d 2.42 (s, 3H), 2.44 (s, 3H), 2.49 (s, 3H),
7.10 (d, J ¼ 8.0 Hz, 1H), 7.26e7.31 (m, 2H), 7.69 (s, 1H), 7.95 (d,
J ¼ 8.0 Hz, 1H), 8.09 (s, 1H); 13C NMR (100 MHz, CDCl3)
d 20.9, 21.6,
21.7, 121.0, 122.8, 123.4, 125.7, 128.0, 130.3, 132.0, 135.5, 135.6, 136.3,
146.0, 151.1, 161.6, 169.4; HRMS (ESI): m/z [M þ H]þ calcd for
C17H16NO2S: 298.0902; found: 298.0905.
2.2.24. 2-(6-Fluorobenzo[d]thiazol-2-yl)-4-methylphenyl pivalate 3tb
1H NMR (400 MHz, CDCl3)
d 1.40 (s, 9H), 2.41 (s, 3H), 6.99 (d,
J ¼ 8.4 Hz, 1H), 7.21 (dt, J ¼ 2.4, 8.8 Hz, 1H), 7.27 (dd, J ¼ 1.6, 8.0 Hz,
4-methyl-2-(6-methylbenzo[d]thiazol-2-yl)-1,3-phenylene diac-
1H), 7.57 (dd, J ¼ 1.6, 8.0 Hz, 1H), 7.91 (d, J ¼ 1.6 Hz, 1H), 7.99 (dd,
etate 4ra. 1H NMR (400 MHz, CDCl3)
d
2.20 (s, 3H), 2.21 (s, 3H), 2.23
J ¼ 4.8, 8.8 Hz, 1H); 13C NMR (100 MHz, CDCl3)
d 20.8, 27.3, 39.2,
(s, 3H), 2.50 (s, 3H), 7.06 (d, J ¼ 8.4 Hz, 1H), 7.30e7.36 (m, 2H), 7.71
107.5 (d, 2JCeF ¼ 26.0 Hz), 114.9 (d, 2JCeF ¼ 25.0 Hz), 123.3, 124.2 (d,
(s, 1H), 7.96 (d, J ¼ 8.4 Hz, 1H); 13C NMR (100 MHz, CDCl3)
d
16.4,
3JCeF ¼ 9.0 Hz), 125.9, 130.7, 132.3, 136.1, 136.5 (d, JCeF ¼ 11.0 Hz),
3
1
4
20.8, 21.1, 21.6, 120.8, 120.9, 121.0, 123.0, 127.8, 129.6, 132.5, 135.8,
135.9, 147.3, 147.8, 151.0, 157.7, 168.6, 169.1; HRMS (ESI): m/z
[M þ H]þ calcd for C19H18NO4S: 356.0957; found: 356.0952.
146.7, 149.9, 160.5 (d, JCeF ¼ 245.0 Hz), 162.9 (d, JCeF ¼ 3.0 Hz),
177.1; HRMS (ESI): m/z [M þ H]þ calcd for C19H19FNO2S: 344.1121;
found: 344.1118.

36
Q. Ding et al. / Journal of Organometallic Chemistry 739 (2013) 33e39
3. Results and discussion
acetoxylation of arenes. The results showed that the benzo[d]
thiazole group directed CeH bond functionalization protocol is
broadly applicable to various substitutes affording corresponding
acetoxylated products in moderate to good yields (Table 2). At first,
the ortho CeH acetoxylation of electronically neutral compound 6-
methyl-2-phenylbenzo[d]thiazole 1b was investigated (Table 2,
entry 2). The di-acetoxylated product 4ba was obtained as the
major product in 63% yield with trace of mono-acetoxylated
product 3ba, and the ratio of 4ba:3ba determined by 1H NMR is
>30:1. Subsequently, all of the substrates bearing either an
electron-donating or electron-withdrawing ortho-substituents at
the phenyl could be applied to form the desired products efficiently
(Table 2, entries 3e14). Furthermore, comparable yields were ob-
tained regardless of the electronic nature of R2. Mono-acetoxylated
products 3caena were isolated in moderate to good yields from
ortho-substituted 2-arylbenzo[d]thiazoles 1cen. For example, the
reaction of 2-(o-tolyl)benzo[d]thiazole 1c under the standard
conditions gave 3ca in 71% yield. A similar yield 70% of the mono-
acetoxylated product 3ka was isolated from the reaction of 2-(2-
chlorophenyl)benzo[d]thiazole 1k. Then, the ortho acetoxylation
of meta-substituted 2-arylbenzo[d]thiazoles was also investigated.
For substrates containing two ortho CeH bonds, the reaction gave
monoacetoxylated product 3 as a major product and the diac-
etoxylated product 4 were isolated in small amounts in most cases.
The efficiency of this transformation was relatively high when an
electron-donating substituent is present (Table 2, entries 15 and 16
vs entries 17 and 19). However, the selectivity of mono- to di-
acetoxylation was comparatively low when substrate with an
electron-donating substituent (Table 2, entries 17 and 18). For
example, the reaction of 2-(3-chlorophenyl)benzo[d]thiazole 1o
containing an electron-withdrawing chloro substituent gave the
mono- and di-acetoxylated products 3oa and 4oa in 60% (isolated)
and 8% (determined by 1H NMR) yields respectively, with better
regioselectivity (Table 2, entry 15). However, the reaction of 2-(m-
Initial investigations were performed using the reaction of 2-
phenylbenzo[d]thiazole 1a with PhI(OAc)2 in CH3CN as the model
reaction and Pd(OAc)2 as the catalyst in sealed tube. The results
showed that the effect of temperature was important for this
transformation. No reaction takes place at room temperature
(Table 1, entry 1). When temperature is changed from room tem-
perature to 60 ꢀC, low yield 24% of mono-acetoxylation product was
observed (Table 1, entry 2). If the temperature rises even further,
the results appear obvious better. When the reaction was per-
formed at 70 ꢀC, 2-phenylbenzo[d]thiazole was converted to diac-
etoxylated product 4aa in a yield of 66% together with a small
amount (12%) of mono-acetoxylation product 3aa (Table 1, entry 3).
Further studies indicate that better result 82% 4aa with 8% 3aa was
isolated when temperature is 90 ꢀC (Table 1, entry 4). Several other
palladium sources, such as Pd(PhCN)2Cl2, Pd(CH3CN)2Cl2,
Pd(PPh3)2Cl2, PdCl2, and Pd3(dba)2 were screened. To our surprise,
the yields were far from satisfactory in this transformation (Table 1,
entries 5e9). Subsequently, we investigated the acetoxylation re-
action in various solvents. The results suggested that the solvent
was also crucial for this transformation. Other solvents, such as
DMF, DMA, THF, dioxane, and toluene were not exhibit higher
catalytic activity (Table 1, entries 10e14). Further examination
showed that changing the amount of PhI(OAc)2 did not effect the
yield distinctly, but affected the ratio of di- to mono-acetoxylated
compound apparently. Reducing the oxidant PhI(OAc)2 loading
decreased the ratio of 4aa to 3aa dramatically, while increasing the
loading improved it visibly (Table 1, entry 4 vs entries 15e17). For
example, diacetoxylated product 4aa was obtained in 84% yield
with only trace of mono-acetoxylation product 3aa when 5 equiv of
PhI(OAc)2 was used (Table 1, entry 17).
With the optimized conditions in hand, we next explored the
effect of the benzo[d]thiazole directing group on the ortho CeH
Table 1
Reaction optimization for the CeH acetoxylation of 1a.a
Entry
Pd (cat)
Solvent
T/ꢀC
Yield (%)b 3aa
Yield (%)b 4aa
1
2
3
4
5
6
7
8
Pd(OAc)2
Pd(OAc)2
Pd(OAc)2
Pd(OAc)2
PdCl2
Pd2(dba)3
Pd(PPh3)2Cl2
Pd(CH3CN)2Cl2
Pd(PhCN)2Cl2
Pd(OAc)2
Pd(OAc)2
Pd(OAc)2
Pd(OAc)2
Pd(OAc)2
Pd(OAc)2
Pd(OAc)2
Pd(OAc)2
CH3CN
CH3CN
CH3CN
CH3CN
CH3CN
CH3CN
CH3CN
CH3CN
CH3CN
DMF
THF
Dioxane
DMA
Toluene
CH3CN
CH3CN
CH3CN
r.t.
NR
24
12
8
12
e
60 ꢀC
70 ꢀC
90 ꢀC
90 ꢀC
90 ꢀC
90 ꢀC
90 ꢀC
90 ꢀC
90 ꢀC
90 ꢀC
90 ꢀC
90 ꢀC
90 ꢀC
90 ꢀC
90 ꢀC
90 ꢀC
e
66
82
e
8
e
Trace
Trace
Trace
60
NR
16
10
30
31
4
e
e
9
e
10
11
12
13
14
15c
16d
17e
Trace
e
Trace
e
20
46
82
84
Trace
a
Reaction conditions: 2-phenylbenzo[d]thiazole 1a (0.3 mmol), PhI(OAc)2 2a (3 equiv, 0.9 mmol), Pd(OAc)2 (5 mol%), solvent (1 mL), 6 h.
b
c
Isolated yield based on 1a.
The ratio of 1a/2a ¼ 1/2.
The ratio of 1a/2a ¼ 1/4.
The ratio of 1a/2a ¼ 1/5.
d
e

Q. Ding et al. / Journal of Organometallic Chemistry 739 (2013) 33e39
37
Table 2
Ortho-Acetoxylation of 2-arylbenzo[d]thiazole 1a
Entry
1c
Starting material 1
Major product
Yield (%)b
Ratio of 3:4
84 (4aa)
e
1a
4aa
2c
63 (4ba)
71 (3ca)
<1:30d
1b
4ba
3
e
1c
3ca
4
5
51 (3da)
70 (3ea)
e
e
1d
3da
1e
3ea
3fa
6
7
50 (3fa)
65 (3ga)
e
e
1f
1g
3ga
8
53 (3ha)
48 (3ia)
56 (3ja)
70 (3ka)
e
e
e
e
e
1h
3ha
9
1i
3ia
3ja
10
11
1j
1k
3ka
12
13
55 (3la)
1l
3la
75 (3ma)
e
(continued on next page)
1m
3ma

38
Q. Ding et al. / Journal of Organometallic Chemistry 739 (2013) 33e39
Table 2 (continued )
Entry
Starting material 1
Major product
Yield (%)b
Ratio of 3:4
14
15
16
17
18
19
70 (3na)
e
1n
3na
68 (3oa þ 4oa)
62 (3pa þ 4pa)
86 (3qa þ 4qa)
90 (3ra þ 4ra)
87 (3sa þ 4sa)
55 (3ta)
5:1e
1o
3oa
3pa
4:1e
1p
1.8:1e
1:1e
1q
3qa
3ra
1r
1s
1t
2.3:1e
>20:1d
3sa
3ta
20
a
Reaction conditions: 2-arylbenzo[d]thiazole 1 (0.3 mmol), PhI(OAc)2 2a (3 equiv, 0.9 mmol), Pd(OAc)2 (5 mol%), CH3CN (1 mL), 90 ꢀC, 6e12 h.
Isolated yield based on 1.
PhI(OAc)2 2a (5 equiv, 1.5 mmol).
Determined by 1H NMR of crude product.
Based on the isolated yield of 3 and 4.
b
c
d
e
tolyl)benzo[d]thiazole 1q containing an electron-donating methyl
yield 53% (Table 2, entry 20). The results suggest that the efficiency
and selectivity is governed by combination of steric and electronic
effect of the substrate.
group under the catalytic conditions afforded 3qa and 4qa in 55%
and 31% yields, respectively (Table 2, entry 17). The difference of the
efficiency and the selectivity is obvious from the electronic effect of
the substituent. Therefore, it is not surprising that 6-chloro-2-(3-
chlorophenyl)benzo[d]thiazole 1p was also acetoxylated in
comparably low yield 62% and relatively high regioselectivity 4/1
(Table 2, entry 16), while 6-chloro-2-(m-tolyl)benzo[d]thiazole 1s
with high yield 87% and low regioselectivity 2.3/1 (Table 2, entry
19). However, in case of 6-fluoro-2-(m-tolyl)benzo[d]thiazole 1t,
afforded mainly the mono-acetoxylated product 3ta in a moderate
Next, we explored the acyloxylation reaction of 6-methyl-2-
phenylbenzo[d]thiazole 1c with PhI(OPiv)2 2b, and found that good
yield was obtained. Then, other acyloxylation reactions were also
investigated as shown in Scheme 1. The results showed that sub-
strates containing an ortho substituent on the aromatic ring, single
product was obtained with good yield. While to those with a meta
substituent on the aromatic ring, good regioselectivity was observed
for acyloxylation of the less sterically hindered o-CeH bond.
Scheme 1. ortho Acyloxylation of 2-arylbenzo[d]thiazole 1 with PhI(OPiv)2 2b (Reaction conditions are the same as in Table 2).

Q. Ding et al. / Journal of Organometallic Chemistry 739 (2013) 33e39
39
References
[1] D. Alberico, M.E. Scott, M. Lautens, Chem. Rev. 107 (2007) 174e238.
[2] K.L. Hull, M.S. Sanford, J. Am. Chem. Soc. 129 (2007) 11904e11905.
[3] G.J. Deng, L. Zhao, C.-J. Li, Angew. Chem. Int. Ed. 47 (2008) 6278e6282.
[4] X. Chen, K.M. Engle, D.H. Wang, J.Q. Yu, Angew. Chem. Int. Ed. 48 (2009)
5094e5115.
[5] O. Daugulis, H.Q. Do, D. Shabashov, Acc. Chem. Res. 42 (2009) 1074e1086.
[6] X.G. Zhang, H.X. Dai, M. Wasa, J.Q. Yu, J. Am. Chem. Soc. 134 (2012) 11948e11951.
[7] D.G. Yu, B.J. Li, Z.J. Shi, Tetrahedron 68 (2012) 5130e5136.
[8] H.Y. Thu, W.Y. Yu, C.M. Che, J. Am. Chem. Soc. 128 (2006) 9048e9049.
[9] J.A. Jordon-Hore, C.C.C. Johansson, M. Gulias, E.M. Beck, M.J. Gaunt, J. Am.
Chem. Soc. 130 (2008) 16184e16186.
[10] T.S. Mei, X. Wang, J.Q. Yu, J. Am. Chem. Soc. 131 (2009) 10806e10807.
[11] K. Matsumoto, H. Sugiyama, Acc. Chem. Res. 35 (2002) 915e926.
[12] X.D. Zhao, E. Dimitrijevic, V.M. Dong, J. Am. Chem. Soc. 131 (2009) 3466e3467.
[13] S.K. Sahoo, A. Banerjee, S. Chakraborty, B.K. Patel, ACS Catal. 2 (2012) 544e551.
[14] A.R. Dick, K.L. Hull, M.S. Sanford, J. Am. Chem. Soc. 126 (2004) 2300e2301.
[15] R. Giri, X. Chen, J.Q. Yu, Angew. Chem. Int. Ed. 44 (2005) 2112e2115.
[16] D. Kalyani, A.R. Dick, W.Q. Anani, M.S. Sanford, Org. Lett. 8 (2006) 2523e2526.
[17] X. Chen, X.-S. Hao, C.E. Goodhue, J.-Q. Yu, J. Am. Chem. Soc. 128 (2006)
6790e6791.
[18] K.L. Hull, W.Q. Anani, M.S. Sanford, J. Am. Chem. Soc. 128 (2006) 7134e7135.
[19] X. Wan, Z. Ma, B. Li, K. Zhang, S. Cao, S. Zhang, Z. Shi, J. Am. Chem. Soc. 128
(2006) 7416e7417.
[20] T.-S. Mei, R. Giri, N. Maugel, J.-Q. Yu, Angew. Chem. Int. Ed. 47 (2008) 5215e5219.
[21] X. Wang, T.S. Mei, J.Q. Yu, J. Am. Chem. Soc. 131 (2009) 7520e7521.
[22] B. Yao, Z.L. Wang, H. Zhang, D.X. Wang, L. Zhao, M.X. Wang, J. Org. Chem. 77
(2012) 3336e3340.
[23] L.V. Desai, K.L. Hull, M.S. Sanford, J. Am. Chem. Soc. 126 (2004) 9542e9543.
[24] L.V. Desai, H.A. Malik, M.S. Sanford, Org. Lett. 8 (2006) 1141e1144.
[25] D.-H. Wang, X.-S. Hao, D.-F. Wu, J.Q. Yu, Org. Lett. 8 (2006) 3387e3390.
[26] G.-W. Wang, T.-T. Yuan, X.-L. Wu, J. Org. Chem. 73 (2008) 4717e4720.
[27] L.V. Desai, K.J. Stowers, M.S. Sanford, J. Am. Chem. Soc. 130 (2008) 13285e13293.
[28] W. Wang, F. Luo, S. Zhang, J. Cheng, Org. Lett. 11 (2009) 3974e3977.
[29] K.J. Stowers, M.S. Sanford, Org. Lett. 11 (2009) 4584e4587.
[30] M.R. Yadav, R.K. Rit, A.K. Sahoo, Chem. Eur. J. 18 (2012) 5541e5545.
[31] A.V. Gulevich, F.S. Melkonyan, D. Sarkar, G. Vladimir, J. Am. Chem. Soc. 134
(2012) 5528e5531.
Scheme 2. Proposed catalytic cycle.
Based onwell-documentedliteratureonpalladium-catalyzedCeH
acyloxylation reaction of arenes [14,23e37], a possible pathway in-
volving a PdII/IV species was proposed in Scheme 2. Firstly, the N of
benzo[d]thiazole coordinated with Pd(OAc)2 to form
a five-
membered cyclic Pd complex A, which might give rise to the PdIV
intermediate B through the oxidation by PhI(OAc)2. Subsequently,
reductive elimination would afford the desired product 3 and
regenerate the active catalyst PdII species for the next catalytic cycle.
Of coursewe stillcannotexcludethemechanistic possibilitythrough a
Pd0/PdII or PdIII pathway in the present acyloxylation reaction [48].
4. Conclusion
In conclusion, we have developed a chelation-assisted Pd-
catalyzed ortho-acyloxylation reaction of the 2-arylbenzo[d]thia-
zole sp2 CeH bond, affording mono- or di-acyloxylation products in
moderate to good yields. A wide substrate scope with good func-
tional group tolerance has been demonstrated. Although the results
are not comparable with the similar approach developed by Yu and
Sanford, a new and useful CeH functionalization/oxidative acy-
loxylation has been described. This method is an alternative route
for the preparation of 2-arylbenzo[d]thiazole derivatives via a CeH
activation mechanism.
[32] E.W. Kalberer, S.R. Whitfield, M.S. Sanford, J. Mol. Catal. A Chem. 251 (2006)
108e113.
[33] N. Chernyak, A.S. Dudnik, C. Huang, V. Gevorgyan, J. Am. Chem. Soc. 132
(2010) 8270e8272.
[34] C. Huang, N. Chernyak, A.S. Dudnik, V. Gevorgyan, Adv. Synth. Catal. 353
(2011) 1285e1305.
[35] W. Wang, C. Pan, F. Chen, J. Cheng, Chem. Commun. 47 (2011) 3978e3980.
[36] Y. Leng, F. Yang, W. Zhu, Y. Wu, X. Li, Org. Biomol. Chem. 9 (2011) 5288e5296.
[37] L. Wang, X.-D. Xia, W. Guo, J.-R. Chen, W.-J. Xiao, Org. Biomol. Chem. 9 (2011)
6895e6898.
[38] I. Hutchinson, M.S. Chua, H.L. Browne, V. Trapani, T.D. Bradshaw,
A.D. Westwell, M.F. Stevens, J. Med. Chem. 44 (2001) 1446e1455.
[39] S. Aiello, G. Wells, E.L. Stone, H. Kadri, R. Bazzi, D.R. Bell, M.F. Stevens,
C.S. Matthews, T.D. Bradshaw, A.D. Westwell, J. Med. Chem. 51 (2008)
5135e5139.
[40] B.S. Tan, K.H. Tiong, A. Muruhadas, N. Randhawa, H.L. Hoo, T.D. Bradshaw,
M.F. Stevens, C.O. Leong, Mol. Cancer Ther. 10 (2011) 1982e1992.
[41] K. Wang, F.P. Guengerich, Chem. Res. Toxicol. 25 (2012) 1740e1751.
[42] Q. Ding, H. Ji, D. Wang, Y. Lin, W. Yu, Y. Peng, J. Organomet. Chem. 711 (2012)
62e67.
Acknowledgments
Financial Supported from National Natural Science Foundation
of China (21002042), Jiangxi Educational Committee (GJJ12169),
and Open Project Program of Key Laboratory of Functional Small
Organic Molecule, Ministry of Education, Jiangxi Normal University
(No. KLFS-KF-201217) is gratefully acknowledged.
[43] Q. Ding, B. Cao, Z. Zong, Y. Peng, J. Comb. Chem. 12 (2010) 370e373.
[44] Q. Ding, B. Cao, X. Liu, Z. Zong, Y. Peng, Green Chem. 12 (2010) 1607e1610.
[45] Q. Ding, X. Liu, J. Yu, Q. Zhang, D. Wang, B. Cao, Y. Peng, Tetrahedron 68 (2012)
3937e3941.
Appendix A. Supplementary data
[46] Q. Ding, X. Liu, H. Wang, M. Chen, Y. Peng, Synthesis 44 (2012) 920e926.
[47] Q. Ding, D. Wang, X. Sang, Y. Lin, Y. Peng, Tetrahedron 68 (2012) 8869e8874.
[48] D.C. Power, T. Ritter, Nat. Chem. 1 (2009) 302e309.
Supplementary data related to this article can be found online at
http://dx.doi.org/10.1016/j.jorganchem.2013.04.026.