A one pot synthesis of annulated carbazole analogs

Article abstract of DOI:10.1016/j.tetlet.2008.07.036

A ZnBr₂-mediated arylation of N-protected 2/3-bromomethylindoles containing an electron-deficient malonylidene unit with arenes at 80 °C led to the formation of arylated products, which on unprecedented 1,5-sigmatropic rearrangement followed by electrocyclization and subsequent aromatization with loss of diethylmalonate furnished the corresponding annulated carbazoles in reasonable yields.

Full text of DOI:10.1016/j.tetlet.2008.07.036

Tetrahedron Letters 49 (2008) 5850–5854
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Tetrahedron Letters
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A one pot synthesis of annulated carbazole analogs
*
Arasambattu K. Mohanakrishnan , Vasudevan Dhayalan, J. Arul Clement,
Ramalingam Balamurugan Radhakrishnan Sureshbabu, Natarajan Senthil Kumar
Department of Organic Chemistry, University of Madras, Guindy Campus, Chennai 600 025, India
a r t i c l e i n f o
a b s t r a c t
Article history:
A ZnBr2-mediated arylation of N-protected 2/3-bromomethylindoles containing an electron-deficient
malonylidene unit with arenes at 80 °C led to the formation of arylated products, which on unprece-
dented 1,5-sigmatropic rearrangement followed by electrocyclization and subsequent aromatization
with loss of diethylmalonate furnished the corresponding annulated carbazoles in reasonable yields.
Ó 2008 Published by Elsevier Ltd.
Received 7 June 2008
Revised 4 July 2008
Accepted 7 July 2008
Available online 9 July 2008
Keywords:
Arenes
Arylation
1,5-Sigmatropic rearrangement
Electrocyclization
Carbazoles
The discovery of technologically promising electronic and opti-
cal properties in fused aromatic compounds necessitates the devel-
opment of new synthetic routes to such systems.1 Recently, a
plethora of aromatic and heteroaromatic annulation reactions
has been reported.2 Ever since the first isolation of a carbazole
alkaloid,3 organic chemists have been interested in the synthesis
of carbazole and its derivatives, due to their promising biological
activities. Recently, Knölker and Reddy extensively reviewed the
synthesis of biologically active carbazole alkaloids.4 Carbazole
and its annulated derivatives due to their unique optical, electrical,
and chemical properties are often used as functional building
blocks in the construction of organic materials for optoelectronic
devices.5–7 Very recently, several benzo and naphthocarbazole ana-
logs have been explored as potential anticancer agents.8
indole 2 was refluxed in xylenes for 1 h. Removal of the solvent,
followed by column chromatographic purification led to the isola-
tion of carbazole 3a (60%) and diethyl malonate. It is apparent that
compound 2 underwent, a thermally facile 1,5-hydrogen shift to
form intermediate 5, which on electrocyclization followed by sub-
sequent elimination of diethyl malonate16 afforded carbazole 3a
(Scheme 1). The formation of seven-membered lactone 4 might
be realized through loss of ethyl bromide from bromo compound
1, which was confirmed via the formation of 4 (40%) upon refluxing
CO2Et
CO2Et
CO2Et
CO2Et
PhH/ZnBr2
N2, reflux
3a
4
N
N
Even though, a variety of arylation protocols are known for benz-
ylic bromides,9–12 they are yet to be adopted for the arylation of
N-protected bromomethylindoles.13 In continuation of our interest
on synthetic elaboration of N-protected bromomethylindoles,14 we
wanted to prepare N-protected-2-benzylindole 2 from the bromo
compound 1. However, the direct phenylation of bromo compound
Br
Ph
SO2Ph
SO2Ph
2 (20%)
1
CO2Et
O
O
N
N
1
15 in the presence of ZnBr2 in dry benzene at reflux was found to
SO2Ph
3a
SO2Ph
4
be troublesome. Careful column chromatographic separation of the
reaction mixture led to the isolation of benzo[b]carbazole 3a (25%)
and lactone 4 (5%), in addition to the expected 2-benzylindole 2
(20%). The formation of benzo[b]carbazole 3a might only occur
from the benzylindole 2. Hence, the N-phenylsulfonyl-2-benzyl-
EtO2C
CO2Et
Xylenes
reflux, 1 h
Electrocyclization
CO2Et
CO2Et
2
3a
1,5-H shift
N
SO2Ph
5
* Corresponding author. Tel.: +91 44 22202813; fax: +91 44 22352494.
E-mail address: mohan_67@hotmail.com (A. K. Mohanakrishnan).
Scheme 1. Phenylation of bromo compound 1.
0040-4039/$ - see front matter Ó 2008 Published by Elsevier Ltd.
doi:10.1016/j.tetlet.2008.07.036

A. K. Mohanakrishnan et al. / Tetrahedron Letters 49 (2008) 5850–5854
5851
1 with 2 equiv of anhydrous ZnBr2 in dry 1,2-DCE. A survey of the
literature revealed that thermolysis of ethyl 2,4-diacetoxy-6-
bromomethylbenzoate under vacuum led to the formation of 5,7-
diacetoxyphthalide in excellent yield.17
CO2Et
Br
EtO2C
Ar1H
2 eq. ZnBr2
Ar1
1, 2-DCE/reflux
N2
N
SO2Ph
N
Hibino and co-workers utilized base-mediated thermal electro-
cyclization of in situ generated N-protected-2,3-divinylindole at a
moderate temperature for the synthesis of carbazole alkaloids.18
Nevertheless, thermal electrocyclization of the in situ generated
2,3-divinylindole was observed only at very high temperature
(460–500 °C).19 Since, under thermal conditions, the electrocycli-
zation has to occur with N-free-2,3-divinylindole, an elevated tem-
perature was essential. Only when the nitrogen lone pair was
tightly held by an electron withdrawing phenylsulfonyl unit, can
the indole-2,3-divinyl system act as a typical triene, which in turn
promotes smooth electrocyclization at a moderate temperature.20
Being surprised by this annulation sequence promoted by a
facile 1,5-sigmatropic hydrogen shift, we tested this protocol with
SO2Ph
3a-k
1
Scheme 2. Annulation of bromo compound 1 with arenas.
Table 1
Annulation of bromo compound 1 with arenes/heteroarenesa
Entry ArH
Time Product24
(h)
Yieldb (%) mp
R1
R1
N
R2
1
24
1
25cꢀe (158 °C)
50f (180–
184 °C)
SO2Ph
3a R1 = H, R2 = H
3b R1 = Me, R2 = H
3b' R1 = H, R2 = Me
3c R1 = OMe, R2 = H
1
62 (200 °C)
2
3
5
2
40d (212 °C)
N
SO2Ph
3d
OMe
OMe
OMe
OMe
57 (210 °C)
N
SO2Ph
3e
Me
Me
4
5
1
55 (208 °C)
N
Me
SO2Ph
3f
Me
Figure 1. ORTEP diagram of carbazole 3c.
R1
R1
1, 2,
4
2
50, 54,g 47h
(182 °C)
52 (170 °C)
N
R2
SO2Ph
R2
3g R1, R2 = Me
3h R1, R2 = OMe
S
6
7
1
0
N
S
SO2Ph
3i
n
S
S
1.5
2
48 (188 °C)
40 (244 °C)
N
S
n
S
SO2Ph
3j n = 1
3k n = 2
Figure 2. ORTEP diagram of carbazole 3f.
a
Reaction conditions: bromo compound 1 (0.57 mmol), Ar1H (0.68 mmol), ZnBr2
(1.15 mmol), 1,2-DCE (10 mL), 80 °C.
Br
b
CO2Et
Isolated yield after column chromatography.
Benzene was used as solvent.
Lactone 4 (5–10% yield) was also isolated.
The corresponding arylated product was also isolated.
EtO2C
CO2Et
c
d
CO2Et
e
Br
N
f
Product 3b was obtained as an inseparable 1:1 mixture of 3b + 3b0 (based on 1H
SO2Ph
S
NMR integration) of isomeric carbazoles.
7
6
g
Yield obtained using 20 mol % InCl3.
h
Yield obtained using 2 equiv of anhydrous FeCl3.
Scheme 3.

5852
A. K. Mohanakrishnan et al. / Tetrahedron Letters 49 (2008) 5850–5854
Table 2
their yields are summarized in Table 1. Annulation product 3a
was obtained in only 25% yield on reaction with benzene, an unac-
tivated aryl system (Table 1, entry 1). Annulations could be carried
out with different types of aryl/heteroaryl systems to afford the
respective products 3a–k in 25–62% yields. The annulation of 1
with toluene led to an inseparable 1:1 (based on 1H NMR inte-
gration value) isomeric mixture of carbazoles 3b and 3b0 (Table
1, entry 1). However, the annulation was found to be selective with
anisole affording carbazole 3c (Table 1, entry 1).
Annulation of bromo compounds 6 and 7 with arenes/heteroarenesa
Substrate ArH
Time Product24
(h)
Yieldb (%) mp
6
10
3a
25cꢀe (158 °C)
6
4
43d (186 °C)
The annulation of 1 with naphthalene furnished the corre-
sponding naphtho[b]carbazole 3d, which represents an iso-steric
pentacyclic framework of calothrixins.21 In the case of unactivated
aryl systems such as benzene and naphthalene, the seven-mem-
bered lactone 4 was always isolated in minor amounts. As ex-
pected, the annulation yield was found to be better with
activated arenes (entries 1, 3–5). A maximum annulation yield of
62% was observed for anisole. In the case of o/p-xylene, in addition
to ZnBr2, the annulation was also studied using 20 mol % InCl3 as
well as 2 equiv of anhydrous FeCl3. Under these conditions, the
yield of the annulation product 3g was only slightly enhanced with
20 mol % of expensive InCl3. Reduced yields were obtained with
2 equiv of anhydrous FeCl3 (entry 5). Attempted annulation of bro-
mo compound 1 with benzo[b]thiophene led to a complex mixture
(entry 6). However, the annulation of 1 was carried out success-
fully with other heterocycles. Annulation of 1 with bi-thiophene/
ter-thiophene led to the isolation of products 3j and 3k in 48%
and 40% yields, respectively (entry 7). The structure of carbazoles
3c and 3f was confirmed by X-ray analysis22 (Figs. 1 and 2).
The scope and limitations of the annulation reaction were fur-
ther explored with bromo compounds 6 and 723 (Scheme 3).
Similar to the case of bromo compound 1, annulation of iso-
meric 3-bromomethylindole 6 could be performed with unacti-
vated mono- and di-substituted arenes to afford the respective
products 3a–o (Table 2). The ZnBr2-mediated arylation of bromo
compound 6 with naphthalene in 1,2-DCE at 80 °C for 10 h fur-
nished the isomeric naphtho[b]carbazole 3l in 43% yield. Compared
to the bromo compound 1, annulation of 6 with anisole furnished
isomeric carbazole 3g in low yield (45%). However, the annulation
of 6 could be achieved in relatively better yields with p-xylene/1,4-
dimethoxybenzene to afford the respective carbazoles 3g/3h. The
N
SO2Ph
3l
OMe
OMe
6
6
1
2
45e (214 °C)
58e (210 °C)
N
SO2Ph
3m
OMe
OMe
3e
Me
Me
6
6
6
1
54 (228 °C)
Me
N
Me
SO2Ph
3n
R1
1
2
3g R1, R2 = Me
58e (182 °C)
56 (170 °C)
3h R1, R2 = OMe
R2
S
S
2
3
47 (228 °C)
46 (220 °C)
N
S
S
SO2Ph
3o
7
7
S
3p
R
R2
R1
i)
R2
2
2
61 (148 °C)
57 (150 °C)
S
S
S
10 mol% InBr3
R3
1
3q R1 = H, R2, R3 = Me
R3
(or)
S
3r R1, R3 = Me, R2 = H
N
20 mol% ZnBr2
N
1,2-DCE, rt, N2, 4 h
ii) 80 oC, 1 h
SO2Ph
3i
SO2Ph
3i'
65% (1: 0.4)
Similar conditions
S
3i + 3i' 70% ( 0.4:1)
6
7
2
49 (208 °C)
S
S
S
S
Scheme 4. Annulation of bromo compounds 1 and 6 with benzo[b]thiophene.
3s
a
Reaction conditions: bromo compound (0.57 mmol), Ar1H (0.68;mmol), ZnBr2
(1.15 mmol), 1,2-DCE (10 mL), 80 °C.
b
Isolated yield after column chromatography.
Benzene was used as solvent.
Lactone 4 (5–10% yield) was also isolated.
Corresponding arylated product was also isolated.
c
d
S
S
e
i)
8
OMe
1eq. ZnBr2/1,2-DCE
rt, N2, 4 h
S
S
OMe
6
various arenes/heteroarenes. To our delight, bromo compound 1 on
heating with arenes in the presence of 2 equiv of ZnBr2 led to the
isolation of a variety of carbazole derivatives 3a–k, (Scheme 2).
Details such as the nature of the arenes/heteroarenes, condi-
tions employed, and the annulation products obtained along with
ii) 80 oC, 1 h
N
SO2Ph
9 (60%,172 oC)
Scheme 5. Annulation of bromo compound 6 with benzo[c]thiophene 8.

A. K. Mohanakrishnan et al. / Tetrahedron Letters 49 (2008) 5850–5854
5853
CO2Et
EtO2C
CO2Et
EtO2C
Br
Br
N
SO2Ph
10
p-xylene
2,2'-bithiophene
i) 4eq. ZnBr2/1,2-DCE
rt, N2, 2 h
Me
ii) 80 oC, 1 h
Me
S
S
S
Me
S
N
N
Me
SO2Ph
11 (58%, 290 oC)
SO2Ph
12 (54%, 270 oC)
Scheme 6. Bis-annulation of bromo compound 10.
Dimitrakopoulos, C. D.; Purushothaman, S.; Kymissis, J.; Callegari, A.; Shaw, J.
M. Science 1999, 283, 822–824.
annulation of 6 with bi-thiophene afforded expected product 3o in
47% yield. The structures and yields of the annulated products 3p–s
obtained using benzo[thienyl]-2-bromomethylindole 7 are also
presented in Table 2. As expected, the annulation of bromo com-
pound 7 proceeded smoothly with arenes as well as heteroarenes
using ZnBr2 in 1,2-DCE at reflux to afford products 3p–s in 46–
61% yields (Table 2).
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ful with benzo[b]thiophene in 1,2-DCE at reflux (Table 1, entry 6),
the same could be performed in a stepwise manner. The heteroaryl-
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NMR integration) in a slightly enhanced 70% yield (Scheme 4).
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phenyl)-3-(thiophen-2-yl)benzo[c]thiophene 825 followed by ther-
molysis at 80 °C for 1 h led to the isolation of annulation product
926 in 60% yield (Scheme 5).
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´
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Finally, the bis-annulation of bromo compound 1027 was per-
formed with p-xylene/bi-thiophene using 4 equiv of ZnBr2 to afford
heterocycles 11 and 1228 in 58 and 54% yields, respectively
(Scheme 6).
In summary, we have developed a one pot annulation protocol
for indolyl-2/3-methylbromides and benzo[thienyl]-2-bromo-
methylindole containing an electron-deficient malonylidene unit
at the adjacent position. The observed annulation was triggered
by a simple ZnBr2-mediated arylation at 80 °C. The resulting arylat-
ed products, at the same temperature, led to the formation of an in
situ generated triene, which on electrocyclization followed by sub-
sequent aromatization with loss of diethyl malonate afforded the
respective annulated products in reasonable yields. The annulation
methodology developed herein can be utilized with a wide variety
of aryl and heteroaryl systems under mild conditions.
Acknowledgments
We thank DST (SR/S1/OC-37/2005) and UGC (32-194/2006/SR),
New Delhi, for financial support. V.D thanks UGC for a fellowship.
Financial assistance from UGC-potential for excellence is also
acknowledged. The authors thank DST-FIST for high-resolution
NMR facilities.
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C
24H19NO4S: C, 69.05; H, 4.59; N, 3.36; S, 7.68. Found: C, 69.29; H, 4.43; N,
3.48; S, 7.86.
8-(Phenylsulfonyl)-8H-naphtho[2,1-b]carbazole (3l): Yield: 43%; mp 186 °C; 1H
NMR (300 MHz, CDCl3) d 9.05 (s, 1H), 8.69 (s, 1H), 8.67 (d, J = 7.8 Hz, 1H), 8.28
(d, J = 8.4 Hz, 1H), 8.02 (d, J = 7.8 Hz, 1H), 7.84–7.67 (m, 5H), 7.63–7.44 (m, 3H),
7.37–7.29 (m, 2H), 7.21–7.16 (m, 2H); 13C NMR (75.4 MHz, CDCl3) d 139.7,
137.7, 137.5, 133.8, 132.0, 131.7, 130.3, 129.0, 128.7, 128.1, 127.5, 127.4, 127.3,
126.8, 126.6 (2C), 126.5,126.4, 124.3, 122.5, 120.4, 115.4, 113.7, 113.4; MS (EI)
m/z (%): 407 (M+, 39%); Anal. Calcd for C26H17NO2S: C, 76.64; H, 4.21; N, 3.44; S,
7.87. Found: C, 76.47; H, 4.39; N, 3.66; S, 7.65.
5-(Phenylsulfonyl)-2-(thiophen-2-yl)-5H-thieno[3,2-b]carbazole (3o): Yield: 47%;
mp 228 °C; 1H NMR (300 MHz, CDCl3) d 8.64 (s, 1H), 8.32 (d, J = 8.4 Hz, 1H),
8.16 (s, 1H), 7.87–7.79 (m, 3H), 7.52 (s, 1H), 7.50–7.25 (m, 7H), 7.06 (t,
J = 4.4 Hz, 1H); 13C NMR (75.4 MHz, CDCl3) d 140.1, 139.3, 138.5, 137.7, 137.3,
137.0, 135.5, 133.8, 129.0, 128.0, 127.7, 126.5, 126.1, 125.9, 125.3, 125.1, 124.2,
120.0, 115.3, 113.0, 109.3; MS (EI) m/z (%): 445 (M+, 29%); Anal. Calcd for
C
24H15NO2S3: C, 64.69; H, 3.39; N, 3.14; S, 21.59. Found: C, 64.84; H, 3.62; N,
22. Crystallographic data for 3c and 3f have been deposited with the Cambridge
Crystallographic Data Centre as supplementary publication numbers CCDC
685765 and CCDC 685764. Copies of the data may be obtained, free of charge,
on application to CCDC, 12 Union Road, Cambridge, CB2 1EZ, UK (fax: +44
(0)1223 33603 or email: deposit@ccdc.cam.ac.uk).
3.01; S, 21.76.
25. Mohanakrishnan, A. K.; Amaladass, P. Tetrahedron Lett. 2005, 46, 4225–4229.
26. Preparation of 2-(3-(4-methoxyphenyl)benzo[c]thiophen-1-yl)-5-(phenylsulf-
onyl)-5H-thieno[3,2-b]carbazole 9: To
a solution of substrate 6 (0.3 g
0.57 mmol) in dry 1,2-DCE (10 mL), ZnBr2 (0.26 g 1.15 mmol) and 1-(4-
methoxyphenyl)-3-(thiophen-2-yl)benzo[c]thiophene 825 (0.22 g, 0.68 mmol)
were added. The reaction mixture was stirred at room temperature for 4 h and
then refluxed for 1 h under N2 atmosphere. It was then poured over ice-water
(30 mL) containing 1 mL of concd HCl, extracted with chloroform (2 ꢁ 10 mL),
and dried (Na2SO4). Removal of the solvent followed by flash column
chromatography (silica gel, 230–420 mesh, n-hexane/ethyl acetate 99:1) led
to the isolation of compound 9 as a yellow solid (0.21 g, 60%); mp 172 °C; 1H
NMR (300 MHz, CDCl3) d 8.65 (s, 1 H), 8.26 (d, J = 8.1 Hz, 1H), 8.20 (s, 1H), 8.06
(d, J = 8.7 Hz, 1H), 7.85 (d, J = 7.5 Hz, 1H), 7.78–7.70 (m, 3H), 7.65 (s, 1H), 7.57
(d, J = 8.6 Hz, 2H), 7.45–7.12 (m, 6H), 7.05 (t, J = 8.7 Hz, 1H), 6.9 (d, J = 8.4 Hz,
2H), 3.82 (s, 3H); 13C NMR (75.4 MHz, CDCl3) d 159.7, 140.1, 139.3, 137.7,
137.2, 136.2, 136.0, 135.9, 135.2, 133.8, 130.6, 129.0, 127.6, 126.5, 126.2, 126.1,
125.4, 125.3, 124.9, 124.3, 124.2, 121.6, 121.4, 121.0, 119.9, 115.3, 114.8, 112.9,
109.1, 55.5; Anal. Calcd for C35H23NO3S3: C, 69.86; H, 3.85; N, 2.33; S, 15.99.
Found: C, 69.99; H, 3.63; N, 2.51; S, 15.75; HRMS (EI) Calcd for C35H23NO3S3
(M): 601.0840. Found: 601.0843.
23. The bromo compound 6 was prepared from the corresponding aldehyde via
condensation with diethyl malonate using TiCl4/pyridine, followed by allylic
bromination using NBS. For the preparation of bromo compound 7 see: Sha, C.-
K.; Hsu, H.-Y.; Cheng, S.-Y.; Kuo, Y.-L. Tetrahedron 2003, 59, 1477–1481.
24. General procedure for annulation of benzylic bromo compounds 1, 6, and 7: To a
solution of bromo compound (0.57 mmol) in dry 1,2-DCE (10 mL), ZnBr2
(1.15 mmol) and arene/heteroarene (0.68 mmol) were added. The reaction
mixture was then refluxed for the specified time (see Tables 1 and 2) under a
N2 atmosphere, then poured over ice-water (30 mL) containing 1 mL of concd
HCl, extracted with chloroform (2 ꢁ 10 mL), and dried (Na2SO4). Removal of
the solvent followed by flash column chromatographic purification (silica gel,
230–420 mesh, n-hexane/ethyl acetate 99:1) afforded the annulation products.
5-(Phenylsulfonyl)-5H-benzo[b]carbazole (3a): Yield: 25%; mp 158 °C; 1H NMR
(300 MHz, CDCl3) d 8.67 (s, 1H), 8.26 (d, J = 8.4 Hz, 1H), 8.25 (s, 1H), 7.97–7.87
(m, 3H), 7.75 (d, J = 8.1 Hz, 2H), 7.48–7.42 (m, 3H), 7.33–7.30 (m, 2H), 7.19 (t,
J = 8.1 Hz, 2H); 13C NMR (75.4 MHz, CDCl3) d 134.8, 132.4, 132.0, 128.5, 127.8,
125.4, 123.8, 123.2, 123.1, 122.8, 121.7, 121.3, 121.1, 120.7, 120.0, 119.0, 115.4,
113.2, 110.1, 107.0; MS (EI) m/z (%): 357 (M+, 58%); Anal. Calcd for C22H15NO2S:
C, 73.93; H, 4.23; N, 3.92; S, 8.97. Found: C, 73.77; H, 4.41; N, 3.79; S, 8.71.
7,10-Dimethoxy-5-(phenylsulfonyl)-5H-benzo[b]carbazole (3h): Yield: 52%; mp
170 °C; 1H NMR (300 MHz, CDCl3) d 9.03 (s, 1H), 8.64 (s, 1H), 8.27 (d, J = 8.1 Hz,
1H), 7.97 (d, J = 7.8 Hz, 1H), 7.76 (d, J = 8.4 Hz, 2H), 7.44 (t, J = 8.4 Hz, 1H), 7.35–
7.28 (m, 1H), 7.19 (t, J = 7.8 Hz, 3H), 6.70–6.61 (m, 2H), 3.98 (s, 3H), 3.94 (s,
3H); 13C NMR (75.4 MHz, CDCl3) d 149.8, 149.6, 140.0, 137.7, 137.4, 133.7,
128.9, 128.2, 126.7, 126.6, 126.4, 126.1, 124.2, 123.8, 120.7, 115.4, 113.0, 107.0,
103.0, 102.0, 55.9, 55.8; MS (EI) m/z (%): 417 (M+, 81%); Anal. Calcd for
27. Sha, C.-K.; Liu, J.-M.; Chiang, R.-K.; Wang, S.-L. Heterocycles 1990, 31, 603–609.
28. Data for 10-(phenylsulfonyl)-2,7-di(thiophen-2-yl)-10H-dithieno[2,3-b:30,20-h]-
carbazole 12: Yield: 54%; mp 270 °C; 1H NMR (300 MHz, CDCl3) d 8.69 (s,
2H), 8.16 (s, 2H), 7.78 (d, J = 7.5 Hz, 2H), 7.43 (s, 2 ), 7.40–7.26 (m, 7H), 7.06 (t,
J = 3.9 Hz, 2H); 13C NMR (75.4 MHz, CDCl3) d 139.2, 137.5, 137.3, 137.2, 137.0,
133.9, 129.1, 128.0, 126.5, 125.6, 125.4, 125.2, 119.0, 113.8, 108.5; Anal. Calcd
for C30H17NO2S5: C, 61.72; H, 2.94; N, 2.40; S, 27.46. Found: C, 61.92; H, 2.76; N,
2.25; S, 27.61; HRMS (EI) Calcd for
582.9867.
C30H17NO2S5 (M): 582.9863. Found: