Reaction of methyl 2-arylethylcarbamates with thionyl chloride: Formation of benzothiazine and benzo[b]thiophene ring systems

Article abstract of DOI:10.3987/COM-01-9296

The reaction of methyl 2-arylethylcarbamates with thionyl chloride induced a sulfur mediated ring closure to form benzothiazine and benzo[b]thiophene ring systems with concomitant chlorination of the aromatic ring.

Full text of DOI:10.3987/COM-01-9296

HETEROCYCLES, Vol. 55, No. 9, 2001, pp. 1779 - 1788, Received, 10th July, 2001
REACTION OF METHYL 2-ARYLETHYLCARBAMATES WITH
THIONYL CHLORIDE: FORMATION OF BENZOTHIAZINE AND
BENZO[b]THIOPHENE RING SYSTEMS
Kunihiko Mohri,* Yuki Yoshida, Takako Awano, Yoshiaki Takeuchi,
and Kimiaki Isobe
Showa Pharmaceutical University, 3-3165, Higashi-tamagawagakuen, Machida,
Tokyo 194-8543, Japan
Abstract - The reaction of methyl 2-arylethylcarbamates with thionyl chloride
induced a sulfur mediated ring closure to form benzothiazine and benzo[b]-
thiophene ring systems with concomitant chlorination of the aromatic ring.
Thionyl chloride (SOCl2) is well known to be an excellent dehydration reagent. For example, primary
amides form nitriles,1 and N,N-dimethylformamide yield Vilsmeier reagent which is useful for synthesis.2
Bell et al. reported that chlorosulfination of aromatic methyl ethers with SOCl2.3 We tried
chlorosulfination of methyl 2-(3,4-dimethoxyphenyl)ethylcarbamate (1) aiming to obtain sulfinyl chloride
derivative (2), which would cyclize to give dihydrobenzothiazine (3), an analogue of biologically active
benzisothiazolone. However, we found that reaction of 1 with SOCl2 directly gave heterocyclic compound
such as benzothiazine and benzo[b]thiophene. This is entirely different from the report of Krubsack et al. 4
who obtained 3-chloro-2-chlorocarbonylbenzo[b]thiophene by the reaction of cinnamic acid with SOCl2,
and suggested the intermediacy of α-chloro-α-sulfenyl derivative. Here we describe the reaction of

methyl 2-arylethylcarbamates with SOCl2, which revealed sulfur mediated cyclization together with
chlorination reaction.
NHCOOMe MeO
MeO
MeO
MeO
MeO
MeO
N-COOMe
NHCOOMe
S
SOCl
O
1
3
2
Scheme 1
Results and Discussion
Reaction of 1 with SOCl2 was carried out in a sealed tube without a solvent at 100°C for 1 h. It was
interesting that thioheterocyclic compounds were obtained though expected 2 or 3 were not formed.
Chromatography of the reaction mixture gave three cyclized products, a benzothiazine (4) (17%), a 3H-
benzo[b]thiophen-2-one (5) (3%), a benzo[b]thiophene (6) (38%), and two uncyclized chloro derivatives
(8) (9%) and (9) (14%) (Table 1, Entry 1). The structures of the products were elucidated by 1H- and 13 C-
NMR spectra and elementary analyses. When the reaction time was elongated to 5 h, the major product
was the benzothiazine (4) (55%) and a new non-cyclized chlorinated derivative (10) (18%) was produced.
The other by-products were the benzo[b]thiophen-2(3H)-one (5) (4%) and benzo[b]thiophene (6) (7%)
(Entry 2).
Cl
5
Cl
Cl
Cl
Cl
Cl
S
4
4
MeO
MeO
MeO
MeO
Cl
Cl
3
1) SOCl2
100°C
MeO
MeO
MeO
MeO
6
7
5
6
3
O
NHCO2Me
+
+
2
NH
N
S
2) H20
2
CO2Me
S
1
8
7
1
CO2Me
Cl
Cl
Cl
1
4
5
6
Cl
Cl
Cl
Cl
Cl
MeO
MeO
MeO
MeO
MeO
MeO
MeO
MeO
NHCO2Me
+
+
+
+
NHCO2Me
NHCO2Me
NCO2Me
S
Cl
Cl
Cl
Cl
7
8
9
10
Scheme 2
Next we carried out the reaction in octane. The reaction at 100°C for 1 h gave a new benzo[b]thiophene
derivative (7) (28%) along with 6 (9%) and 9 (20%) (Entry 3). When the reaction time was elongated to 5
h, the same compounds as in Entry 2 were produced though the ratio of the products was different.

Table 1. Reaction of methyl 2-(3,4-dimethoxyphenyl)ethylcarbamate (1) with SOCl2
Products (Yield, %)
Conditions
Solvent
Entry
Time
4
5
6
7
8
9
10
-
-
-
14
-
1
neat
1 h
5 h
1 h
5 h
17
3
38
9
-
neat
18
-
2
3
55
-
4
-
7
9
-
octane
20
-
28
-
-
4
octane
30
5
23
5
Heating of methyl 2-(3-methoxyphenyl)ethylcarbamate (11) with SOCl2 at 100°C for 6 h gave 12, 13, 14,
and 15 in 5, 12, 8 and 7% yields, respectively (see Scheme 3, Table 2). The structures of 12, 13, and 14
were deduced on the basis of 1H-, 13C-NMR, and MS spectral analyses. The position of chlorine atoms on
the aromatic ring in the products (12, 13, and 14) was determined by the NOE correlation spectroscopy
(NOESY). The product (14) showed a cross peak between 4-H (δ6.77, d, J=8.9 Hz) and OMe (δ 3.88, s),
thus confirming that chlorine atoms were introduced at ortho and para position to the OMe group.
However, in 12 and 13, the cross peaks between the aromatic proton (12: δ 7.33, s; 13: δ 7.62, s) and
methoxyl protons (12: δ 3.99, s; 13: δ 3.92, s) were not observed implying that the two chlorine atoms
were introduced at the ortho positions of the OMe group.
Cl
Cl
Cl
Cl
Cl
S
MeO
MeO
Cl
MeO
MeO
Cl
Cl
SOCl2, 100°C
in sealed tube
NHCO2Me
+
+
NH
NHCO2Me
N
Cl
CO2Me
S
CO2Me
12
11
13
14
MeO
Cl
+
NHCO2Me
Cl
Scheme 3
15
In order to clarify the pathway of constructing the benzothiophene and benzothiazine rings we carried out
several experiments. Similar reactions of methyl 2-(4-methoxyphenyl)ethylcarbamate (16) and methyl 2-
phenylethylcarbamate (18), the both of which do not have OMe group which is activated on the ortho
position of the ethylcarbamate side chain, gave neither benzothiophene nor benzothiazine derivatives,

Table 2. Reaction of methyl 2-(3-methoxyphenyl)ethylcarbamate (11) with SOCl2
Products (Yield, %)
Conditions
Solvent
Entry
12
13
14
15
11
-
Time
6 h
neat
neat
1
5
12
-
8
-
7
-
-
2
3
4
21h
9 h
14
16
19
octane
octane
-
-
6
8
41
-
-
-
20 h
instead produced urea derivatives (17 and 19) in low yields, with considerable recovery of the starting
materials, respectively. Methyl 2-(6-chloro-3,4-dimethoxyphenyl)ethylcarbamate (9), on further reaction
with SOCl2, did not yield any cyclized product and merely produced further chlorinated compounds (20
(43%), 10 (21%), and 21 (19%)). Treatment of the benzothiophene (6) with SOCl2 at 100°C caused a
hydrolytic elimination of the carbamate group to yield 5 (16%) and, at the same time, the ring expansion
reaction to 4 was observed (15%). It is confirmed that the thioheterocyclization requires OMe group
which is attached at the meta position of the ethylcarbamate side chain.
O
SOCl2, octane
N
H
N
CO2Me
NH
100°C
in sealed tube
R
R
R
CO2Me
17 R=OMe
19 R=H
16 R=OMe
18 R=H
Cl
Cl
Cl
Cl
Cl
1) SOCl2
100°C, 5 h
O
Cl
MeO
MeO
MeO
MeO
MeO
Cl
+
9
+
NHCO2Me
NCO2Me
NHCO2Me
2) H20
Cl
MeO
Cl
10 (21%)
20 (43%)
21 (19%)
SOCl2
100°C, 12 h
4
(15%)
5
(16%)
+
6 (8%)
+
6
Scheme 4
Tables 1 and 2 suggested that the first step of the reaction leading to heterocycles from 1 and 11 should be
formation of the thio intermediate (i) by the attack of SOCl2 to the para position of OMe group. The
intermediate (i) cyclizes to the benzo[b]thiophene (6 and 13), which would give the benzothiazine (4 and

12) by the ring expansion via the thioaziridine intermediate (ii) (Scheme 5). Chlorination of aromatic ring
could be subsequent step of sulfenylation, because none of the chlorinated products was obtained from 16
and 18.
Cl
H
(Cl)
H
Cl
(Cl)
Cl
MeO
MeO
MeO
MeO
Cl
H
+
NH
S
N-CO2Me
S
X
CO2Me
Cl
i (X=Cl or other)5
ii
Scheme 5
EXPERIMENTAL
Unless otherwise stated, the following procedure was adopted. Melting points were determined on a
Yanaco micro-melting point apparatus and are uncorrected. IR spectra were recorded on a JASCO IR-810
1
13
spectrophotometer and data are given in cm-1. H- and C-NMR spectra were taken with a JEOL JNM-
EX90 (90 MHz for 1H and 22.5 MHz for 13C), JEOL JNM-AL300 (300 MHz for 1H and 75 MHz for 13C)
1
or JNM-α500 (500 MHz for H) spectrometer in CDCl3 solutions with TMS as an internal standard and
the chemical shifts are given in δ values. MS and HRMS were taken with a JEOL JMS D-300 and JEOL
JMS-HX110A spectrometer and given in m/z. Column chromatography (CC) and medium pressure
column chromatography (MPLC) were done on silica gel. Elemental analyses were performed with a
YANACO MT-3.
Reaction of Methyl 2-(3,4-dimethoxyphenyl)ethylcarbamate (1) with SOCl2
i) A mixture of
SOCl2 (3 mL, 41 mmol) and 1 (200 mg, 0.83 mmol) was heated in a sealed tube at 100°C for 1 h. After
cooling, the reaction mixture was poured into water (50 mL), and extracted with CHCl3. The extract was
dried over Na2SO4, and concentrated in vacuo. The residue was chromatographed with AcOEt-hexane
(1:2), the solvent of the fraction was evaporated. The crude product was purified by MPLC with AcOEt-
hexane (1:4, 1:1) to give 4 (58 mg, 17%), 5 (9 mg, 3%), 6 (118 mg, 38%), 8 (23 mg, 9%) and 9 (32 mg,
14%).
3,4,5,8-Tetrachloro-6,7-dimethoxy-2-methoxycarbonyl-2H-1,2-benzothiazine
(4):
Yellow

amorphous. IR (CHCl3): 1720. 1H-NMR: 4.00 (s, 6H), 3.95 (s, 3H). 13C-NMR: 183.8, 162.3, 153.3, 150.7,
35
129.7, 127.9, 127.5, 121.1, 86.6, 61.4x2, 54.6. MS: m/z 403 (M+ for Cl), 405 (M++2), 407 (M++4).
HRMS: Calcd for C12H9NO4Cl4S: 402.9004. Found: 402.8997. 3,3,4,7-Tetrachloro-5,6-dimethoxybenzo-
1
13
[b]thiophen-2(3H)-one (5): Pale yellow gum. IR (KBr): 1730. H-NMR: 4.02 (s, 3H), 3.96 (s, 3H). C-
35
NMR: 190.3, 153.3, 150.3, 128.2, 127.6, 127.4, 121.4, 82.7, 61.4x2. MS: m/z 346 (M+ for Cl), 348
(M++2), 350 (M++4). HRMS: Calcd for C10H6O3Cl4S: 345.8789. Found: 345.8733. Methyl (3,4,7-
trichloro-5,6-dimethoxybenzo[b]thienyl)carbamate (6): Pale yellow prisms. mp 170-172°C (Et2O-hexane).
IR (KBr): 3400, 1740. 1H-NMR: 7.53 (br s, 1H), 3.96 (s, 3H), 3.94 (s, 3H), 3.90 (s, 3H). 13C-NMR: 153.1,
35
149.5, 147.1, 136.2, 128.8, 126.6, 119.8, 105.1, 102.0, 61.6, 61.2, 53.5. MS: m/z 369 (M+ for Cl), 371
(M++2), 373 (M++4). HRMS: Calcd for C12H10NO4Cl3S: 368.9393. Found: 368.9392. Anal. Calcd for
C12H10NO4Cl3S: C, 38.89; H, 2.72; N, 3.78. Found: C, 38.61; H, 2.76; N, 3.75. Methyl 1-chloro-2-(6-
chloro-3,4-dimethoxyphenyl)ethylcarbamate (8): Reddish purple gum. IR (CHCl3): 3450, 1725. 1H-NMR:
7.02 (s, 1H), 6.84 (s, 1H), 5.68-5.35 (m, 1H), 5.10 (br s, 1H), 3.89 (s, 3H), 3.87 (s, 3H), 3.81-3.58 (m, 2H),
3.67 (s, 3H). 13C -NMR: 156.7, 149.7, 148.3, 127.5, 124.4, 112.2, 110.7, 58.3, 56.2x2, 52.4, 47.6. MS: m/z
35
307 (M+ for Cl), 309 (M++2), 311 (M++4). Methyl 2-(6-chloro-3,4-dimethoxyphenyl)-ethylcarbamate
(9): Light yellow prisms. mp 76-78°C (Et2O-hexane). IR (KBr): 3340, 1695. 1H-NMR: 6.84 (s, 1H), 6.70
13
(s, 1H), 4.89 (br s, 1H), 3.85 (s, 6H), 3.67 (s, 3H), 3.59-3.21 (m, 2H), 3.05-2.72 (m, 2H). C -NMR:
35
156.9, 148.1, 147.7, 128.0, 124.8, 113.3, 112.5, 66.0x2, 51.9, 40.8, 33.4. MS: m/z 273 (M+ for Cl), 275
(M++2). HRMS: Calcd for C12H16NO4Cl: 273.0767. Found: 273.0772.
ii) A mixture of SOCl2 (3 mL, 41 mmol) and 1 (200 mg, 0.83 mmol) was heated in a sealed tube at 100°C
for 5 h and worked up as described above to give 4 (186 mg, 55%), 5 (12 mg, 4%), 6 (22 mg, 7%) and 10
(56 mg, 18%). 1,2,2-Trichloro-N-methoxycarbonyl-2-(6-chloro-3,4-dimethoxyphenyl)ethylimine (10):
Pale yellow gum. IR (CHCl3): 1750. 1H-NMR: 7.62 (s, 1H), 6.93 (s, 1H), 3.96 (s, 3H), 3.93 (s, 3H), 3.91
13
(s, 3H). C -NMR: 157.1, 152.6, 149.8, 148.5, 128.2, 124.5, 114.2, 113.1, 88.1, 56.2x2, 55.4. MS: m/z

373 (M+ for 35Cl), 375 (M++2), 377 (M++4).
iii) A solution of 1 (200 mg, 0.83 mmol) and SOCl2 (1.5 mL, 21 mmol) in octane (1.5 mL) was heated in
a sealed tube at 100°C for 1 h. After cooling, the reaction mixture was poured into water (50 mL) and
extracted with CHCl3. The extract was dried over Na2SO4 and concentrated in vacuo. The residue was
chromatographed with AcOEt-hexane (1:2), the solvent of the fraction was evaporated. The crude product
was purified by MPLC with AcOEt-hexane (1:4, 1:1) to give 6 (28 mg, 9%), 7 (79 mg, 28%) and 9 (46
mg, 20%). Methyl (3,7-dichloro-5,6-dimethoxybenzo[b]thienyl)carbamate (7): Pale yellow gum. IR
(CHCl3): 3450, 1730. 1H-NMR: 7.37 (br s, 1H), 7.00 (s, 1H), 3.95 (s, 3H), 3.91 (s, 3H), 3.89 (s, 3H). 13C -
NMR: 153.1, 152.9, 143.5, 134.5, 130.5, 124.0, 121.5, 102.4, 101.1, 61.2, 56.3, 53.5. MS: m/z 335 (M+
for 35Cl), 337 (M++2), 339 (M++4). HRMS: Calcd for C12H11NO4Cl2S: 334.9783. Found: 334.9756.
iv) A solution of 1 (200 mg, 0.83 mmol) and SOCl2 (1.5 mL, 21 mmol) in octane (1.5 mL) was heated in a
sealed tube at 100°C for 5 h and worked up as described above to give 4 (102 mg, 30%), 5 (15 mg, 5%), 6
(71 mg, 23%) and 10 (16 mg, 5%).
Reaction of Methyl 2-(3-methoxyphenyl)ethylcarbamate (11) with SOCl2
i) A mixture of 11
(300 mg, 1.44 mmol) and SOCl2 (3.1 mL, 42 mmol) was stirred in a sealed tube at 100°C for 6 h. The
mixture was concentrated in vacuo and purified by CC with AcOEt-hexane (1:8) to give 12 (29 mg, 5%),
13 (60 mg, 12%), 14 (32 mg, 8%) and 15 (26 mg, 7%). 3,4,5,7-Tetrachloro-6-methoxy-2-methoxy-
carbonyl-2H-1,2-benzothiazine (12): Yellow gum. IR (CHCl3): 1690. 1H-NMR: 7.33 (s, 1H), 3.99 (s, 3H),
3.96 (s, 3H). 13C-NMR: 184.5, 162.3, 152.9, 133.4, 131.7, 130.0, 129.7, 122.4, 85.5, 61.1, 60.3. MS: m/z
373 (M+ for 35Cl), 375 (M++2), 377 (M++4). HRMS: Calcd for C11H7NO3Cl4S: 372.8900. Found: 372.8950.
Methyl (3,4,6-trichloro-5-methoxybenzo[b]thienyl)carbamate (13): Light yellow prisms. mp 179-181°C
1
13
(Et2O-hexane). IR (KBr): 1730. H-NMR: 7.62 (s, 1H), 7.55 (br s, 1H), 3.92 (s, 3H), 3.89 (s, 3H). C-
NMR: 153.1, 150.7, 136.6, 129.8, 129.7, 125.1, 121.8, 121.7, 101.3, 60.9, 53.6. HRMS: Calcd for
C11H8NO3Cl3S: 338.9288. Found: 338.9278. Methyl 2-(2,6-dichloro-3-methoxyphenyl)ethylcarbamate

(14): Orange gum. IR (CHCl3): 3450, 1720. 1H-NMR: 7.25 (d, J = 8.9 Hz, 1H), 6.77 (d, J = 8.9 Hz, 1H),
4.82 (br s, 1H), 3.88 (s, 3H), 3.66 (s, 3H), 3.55-3.32 (m, 2H), 3.32-3.05 (m, 2H). 13C -NMR: 157.0,
154.2, 135.8, 127.9, 126.6, 124.1, 110.8, 56.4, 52.0, 39.5, 31.8. HRMS: Calcd for C11H13NO3Cl2:
277.0273. Found: 277.0300. Methyl 2-(4,6-dichloro-3-methoxyphenyl)ethylcarbamate (15): Orange gum.
1
IR (CHCl3): 3450, 1720. H-NMR: 7.37 (s, 1H), 6.78 (s, 1H), 4.76 (br s, 1H), 3.88 (s, 3H), 3.67 (s, 3H),
13
3.59-3.19 (m, 2H), 3.19-2.78 (m, 2H). C -NMR: 157.1, 153.8, 135.9, 130.5, 125.3, 121.4, 114.1, 56.4,
52.2, 40.5, 34.0. HRMS: Calcd for C11H13NO3Cl2: 277.0272. Found: 277.0305.
ii) A mixture of 11 (300 mg, 1.44 mmol) and SOCl2 (3.1 mL, 42 mmol) was stirred in a sealed tube at
100°C for 21 h and worked up as described above to give 12 (74 mg, 14%).
iii) A solution of 11 (300 mg, 1.44 mmol) and SOCl2 (3.1 mL, 42 mmol) in octane (3 mL) was heated in a
sealed tube at 100°C for 9 h. The mixture was concentrated in vacuo and subjected to CC with AcOEt-
hexane (1:8) to give 12 (78 mg, 16%), 13 (28 mg, 6%) with recovery of 11 (122 mg, 41%).
iv) A solution of 11 (300 mg, 1.44 mmol) and SOCl2 (3.1 mL, 42 mmol) in octane (3 mL) was heated in a
sealed tube at 100°C for 20 h and worked up as described above to give 12 (113 mg, 19%) and 13 (39 mg,
8%).
Reaction of Methyl 2-(4-methoxyphenyl)ethylcarbamate (16) with SOCl2
A solution of 16 (300
mg, 1.44 mmol) and SOCl2 (3.1 mL, 42 mmol) in octane (3 mL) was heated in a sealed tube at 100°C for
29 h. The mixture was concentrated in vacuo and the resulting residue was purified by CC with AcOEt-
hexane (1:5) to give 17 (18 mg, 7%) with recovery of 16 (246 mg, 82%). N,N’-Bis(4-methoxy-
phenylethyl)-N-methoxycarbonylurea (17): Colorless gum. IR (CHCl3): 3300, 1730, 1680. 1H-NMR: 8.62
(br t, J = 4.0 Hz, 1H), 7.38-6.71 (m, 8H), 4.10-3.31 (m, 4H), 3.78 (s, 6H), 3.69 (s, 3H), 2.98-2.60 (m, 4H).
13C -NMR: 158.2x2, 156.5, 154.1, 131.0, 130.9, 129.9x2, 129.7x2, 113.9x2, 113.8x2, 55.2x2, 53.3, 45.4,
42.2, 35.0, 34.5. MS: m/z 386 (M+). HRMS: Calcd for C21H26N2O5: 386.1842. Found: 386.1863.
Reaction of Methyl 2-phenylethylcarbamate (18) with SOCl2
A solution of 18 (300 mg, 1.7

mmol) and SOCl2 (3.6 mL, 49 mmol) in octane (3.6 mL) was heated in a sealed tube at 100°C for 140 h.
The resulting mixture was concentrated in vacuo and the residue was purified by CC with AcOEt-hexane
(1:6) to give 19 (39 mg, 14%) with recovery of 18 (149 mg, 50%). N-Methoxycarbonyl-N,N’-bis-
1
(phenylethyl)urea (19): Colorless gum. IR (CHCl3): 3300, 1720, 1680. H-NMR: 8.64 (br t, J = 4.0 Hz,
13
1H), 7.41-7.08 (m, 10H), 4.12-3.80 (m, 2H), 3.65 (s, 3H), 3.70-3.39 (m, 2H), 2.99-2.72 (m, 4H). C-
NMR: 156.5, 154.1, 139.0, 138.9, 128.9x2, 128.7x2, 128.5x2, 128.3x2, 126.4, 126.3, 53.3, 45.2, 42.0,
35.9, 35.5. HRMS: Calcd for C19H22N2O3: 326.1631. Found: 326.1641.
Reaction of Methyl 2-(2-chloro-4,5-dimethoxyphenyl)ethylcarbamate (9) with SOCl2
A
mixture of 9 (200 mg, 0.73 mmol) and SOCl2 (3 mL, 41 mmol) was stirred in a sealed tube at 100°C for 5
h. The reaction mixture was poured into water (50 mL) and extracted with AcOEt. The extract was dried
over Na2SO4, and evaporated in vacuo. The residue was purified by CC with AcOEt-hexane (1:2), the
solvent of the fraction was evaporated. The crude product was purified by MPLC with AcOEt-hexane
(1:2) to give 20 (101 mg, 43%), 10 (57 mg, 21%) and 21 (47 mg, 19%). Methyl 2-chloro-2-(6-chloro-3,4-
1
dimethoxyphenyl)-1-oxoethylcarbamate (20): Light yellow gum. H-NMR: 8.19 (br s, 1H), 7.02 (s, 1H),
6.88 (s, 1H), 6.31 (s, 1H), 3.88 (s, 6H), 3.82 (s, 3H). 13C -NMR: 166.3, 151.1, 150.3, 148.3, 125.3, 124.6,
35
112.3, 111.8, 56.9, 56.2x2, 53.4. MS: m/z 321 (M+ for Cl), 323 (M++2), 325 (M++4). Methyl 1,2-
1
dichloro-2-(6-chloro-3,4-dimethoxyphenyl)ethenylcarbamate (21): Yellow gum. H-NMR: 6.85 (s, 2H),
13
3.88 (s, 3H), 3.85 (s, 3H), 3.66 (s, 3H). C -NMR: 153.6, 150.4, 147.9, 129.2, 125.9, 125.7, 124.2,
112.3x2, 56.2x2, 53.1. MS: m/z 339 (M+ for 35Cl), 341 (M++2), 343 (M++4).
Reaction of Methyl (3,4,7-trichloro-5,6-dimethoxybenzo[b]thienyl)carbamate (6) with SOCl2
A
mixture of 6 (60 mg, 0.16 mmol) and SOCl2 (0.35 mL, 5 mmol) was stirred in a sealed tube at 100°C for
12 h. The resulting mixture was concentrated in vacuo and the residue was purified by CC with AcOEt-
hexane (1:10) to give 4 (10 mg, 15%), 5 (9 mg, 16%), with recovery of 6 (5 mg, 8%).
REFERENCES AND NOTES

1. L. A. Paquette, "Encyclopedia of Reagent for Organic Synthesis," John Wiley & Sons, Inc. New York,
1995; Vol. 7, pp. 4873-4876 and references cited therein.
2. a) L. F. Fieser and M. Fieser, "Reagents for Organic Synthesis," John Wiley & Sons, Inc. New York,
1967; pp. 286-289 and references cited therein; b) M. Fieser, "Reagents for Organic Synthesis,"
John Wiley & Sons, Inc. New York, 1986; Vol. 12, p. 204.
3. a) K. H. Bell and K. F. McCaffery, Aust. J. Chem., 1992, 45, 1213; b) K. H. Bell, ibid., 1985, 38, 1209.
4. T. Higa and A. J. Krubsack, J. Org. Chem., 1975, 40, 3037.
5. Bell reported that sulfinyl chloride, sulfide, disulfide derivatives were obtained by the reaction of
aromatic methyl ether with thionyl chloride. The intermediate in our case is considered that one of
these functions, though it is not clear.