7714
T. Fujita et al. / Tetrahedron 63 (2007) 7708–7716
(161.1 mg, 0.56 mmol) in acetonitrile (4 ml) and chloramine
T (200.0 mg, 0.71 mmol) in acetonitrile (5 ml) to afford 1-
trimethylsilyl-5-(N-p-tosyl)iminothianthrene (2c) (169.9 mg)
and 1-trimethylsilyl-10-(N-p-tosyl)iminothianthrene (3c)
(40.0 mg) in 67 and 16% yields, respectively (reaction
time: 1 h). Compound 2c: mp 197–199 ꢀC (colorless crystals
from chloroform–hexane); 1H NMR (CDCl3) d 0.44 (s,
9H), 2.39 (s, 3H), 7.26–7.28 (m, 2H), 7.44–7.53 (m, 3H),
7.59–7.61 (m, 1H), 7.65–7.68 (m, 1H), 7.91–7.96 (m,
4H); 13C NMR (CDCl3) d ꢁ0.3, 21.4, 125.4, 126.2, 126.3,
128.1, 129.0, 129.4, 129.5, 130.3, 130.9, 135.1, 135.6,
136.2, 136.7, 141.0, 142.0, 142.1; IR (KBr) n¼1280,
1140, 1080, 980 cmꢁ1. Anal. Calcd for C22H23NSiS3O2:
C, 57.73; H, 5.06; N, 3.06. Found: C, 57.96; H, 4.86; N,
3.14.
mp 245–250 ꢀC (dec) (colorless crystals); 1H NMR
(CDCl3) d 2.42 (s, 3H), 7.29 (d, J¼8.4 Hz, 2H), 7.65 (dd,
J1¼8.6 Hz, J2¼1.8 Hz, 2H), 7.73 (d, J¼8.4 Hz, 2H), 7.81
(d, J¼1.6 Hz, 2H), 7.91 (d, J¼8.4 Hz, 2H); 13C NMR
(CDCl3) d 21.5, 125.9, 126.3, 127.1, 129.6, 131.4, 132.3,
132.4, 133.2, 140.6, 142.6; IR (KBr) n¼1430, 1300, 1150,
1090, 970 cmꢁ1. Anal. Calcd for C19H13NS3O2Br2: C,
42.00; H, 2.41; N, 2.58. Found: C, 42.24; H, 2.48; N, 2.86.
4.3. General procedure of oxidation of thianthrene
derivatives with m-CPBA
To a stirred solution of thianthrene derivatives 1 in dichloro-
methane (2 ml), 1.1 equiv m-CPBA dissolved in dichloro-
methane (4 ml) was added under ice cooling. After 2 h, the
reaction mixture was washed with saturated solution of
sodium bicarbonate to remove m-chlorobenzoic acid and
m-CPBA, washed with water, and dried over anhydrous
MgSO4. After removal of solvent under reduced pressure,
purification was made by chromatography on silica gel elut-
ing with ethyl acetate–hexane (1:3) to afford the correspond-
ing thianthrene sulfoxides 4 and 5 as colorless crystals.
4.2.3. N-Tosylimination of 2-bromothianthrene (1e). The
above procedure was employed by using 1e (291.5 mg,
0.99 mmol) in acetonitrile (5 ml) and chloramine T
(331.2 mg, 1.12 mmol) in acetonitrile (8 ml) to afford 2-
bromo-5-(N-p-tosyl)iminothianthrene (2e) (136.8 mg) and
2-bromo-10-(N-p-tosyl)iminothianthrene (3e) (83.5 mg) in
30 and 18% yields, respectively, with recovery (77.7 mg,
27%) of starting material (reaction time: 1 day). Compound
2e: mp 220–223 ꢀC (dec) (colorless crystals from chloro-
4.3.1. 1-Methylthianthrene 5-oxide (4b). Yield 54%; mp
1
128–129 ꢀC (colorless solid from chloroform–hexane); H
1
form–hexane); H NMR (CDCl3) d 2.41 (s, 3H), 7.29 (d,
NMR (CDCl3) d 2.51 (s, 3H), 7.28 (d, J¼7.6 Hz, 1H),
7.37–7.44 (m, 2H), 7.51 (dt, J1¼7.6 Hz, J2¼1.2 Hz, 1H),
7.61 (dd, J1¼7.2 Hz, J2¼0.4 Hz, 1H), 7.76 (d, J¼7.6 Hz),
7.89 (dd, J1¼7.6 Hz, J2¼1.2 Hz, 1H); 13C NMR d 20.0,
122.1, 124.3, 128.0, 128.4, 129.2, 129.7, 131.1, 137.3,
137.5, 141.2, 141.3, 141.6; IR (KBr) n¼1445, 1073, 1047,
1035 cmꢁ1. Anal. Calcd for C13H10OS2: C, 63.38; H, 4.09;
N, 0.00. Found: C, 63.24; H, 3.87; N, 0.00.
J¼8.4 Hz, 2H), 7.47–7.55 (m, 2H), 7.61–7.67 (m, 2H),
7.73 (d, J¼8.4 Hz, 1H), 7.81 (d, J¼2.0 Hz, 1H), 7.89–7.94
(m, 3H); 13C NMR (CDCl3) d 21.5, 125.6, 125.9, 126.3,
126.3, 127.0, 129.3, 129.5, 129.6, 129.6, 131.2, 132.1,
133.4, 133.9, 140.8, 142.4; IR (KBr) n¼1430, 1290, 1140,
1090, 970 cmꢁ1. Anal. Calcd for C19H14NS3O2Br: C,
49.14; H, 3.04; N, 3.02. Found: C, 49.14; H, 3.08; N, 3.05.
Compound 3e: mp 197–201 ꢀC (colorless crystals from
chloroform–hexane); 1H NMR (CDCl3) d 2.42 (s, 3H),
7.31 (d, J¼8.0 Hz, 2H), 7.49–7.58 (m, 4H), 7.65 (dd,
J1¼7.2 Hz, J2¼1.4 Hz, 1H), 7.82 (d, J¼2.0 Hz, 1H), 7.92–
7.95 (m, 3H). 13C NMR (CDCl3) d 21.5, 123.3, 125.9,
126.3, 128.4, 129.3, 129.3, 129.6, 129.7, 129.9, 130.7,
131.2, 133.8, 134.1, 136.1, 140.8, 142.6; IR (KBr)
n¼1440, 1290, 1150, 1090, 960 cmꢁ1. Anal. Calcd for
C19H14NS3O2Br: C, 49.14; H, 3.04; N, 3.02. Found: C,
49.20; H, 3.00; N, 3.14.
4.3.2. 1-Methylthianthrene 10-oxide (5b). Yield 30%; mp
145–146 ꢀC (colorless crystals from chloroform–hexane);
1H NMR (CDCl3) d 2.83 (s, 3H), 7.24–7.26 (m, 1H), 7.35
(t, J¼7.6 Hz, 1H), 7.46–7.53 (m, 2H), 7.56–7.58 (m, 1H),
7.72–7.74 (m, 1H), 7.98–8.00 (m, 1H); 13C NMR (CDCl3)
d 19.5, 126.9, 127.4, 128.5, 130.0, 130.1, 130.5, 131.4,
133.1, 133.3, 136.0, 136.8, 139.7; IR (KBr) n¼1443, 1053,
1021 cmꢁ1. Anal. Calcd for C13H10OS2: C, 63.38; H, 4.09;
N, 0.00. Found: C, 63.12; H, 3.74; N, 0.00.
4.2.4. N-Tosylimination of mixture of 2,7- and 2,8-dibro-
mothianthrene (1f and 1f0). The above procedure was em-
ployed by using 1f, 1f0 (161.7 mg, 0.43 mmol) in acetonitrile
(10 ml), and chloramine T (150.6 mg, 0.54 mmol) in aceto-
nitrile (5 ml). The reaction mixture was separated by HPLC
using methanol–water (10:1) as the eluant to afford 2,7-di-
bromo-5-(N-p-tosyl)iminothianthrene 2f (39.1 mg) and
2,7-dibromo-10-(N-p-tosyl)iminothianthrene 2f0 (53.7 mg)
in 17 and 23% yields, respectively (reaction time: 1 day).
Compound 2f: mp 199–201 ꢀC (colorless crystals); 1H
NMR (CDCl3) d 2.42 (s, 3H), 7.31 (d, J¼8.0 Hz, 2H), 7.49
(d, J¼8.0 Hz, 1H), 7.58 (dd, J1¼8.2 Hz, J2¼2.2 Hz, 1H),
7.65 (dd, J1¼8.4 Hz, J2¼2.0 Hz, 1H), 7.76 (d, J¼8.4 Hz,
1H), 7.80–7.82 (m, 2H), 7.91–7.94 (m, 2H); 13C NMR
(CDCl3) d 21.5, 123.7, 125.9, 126.3, 127.1, 128.6, 129.7,
130.8, 131.8, 132.3, 132.4, 133.0, 134.4, 136.0, 140.7,
4.3.3. 1-Trimethylsilylthianthrene 5-oxide (4c). Yield
50%; mp 118–120 ꢀC (colorless crystals from chloroform–
hexane); 1H NMR (CDCl3) d 0.46 (s, 9H), 7.42 (dt,
J1¼7.4 Hz, J2¼1.2 Hz, 1H), 7.50–7.58 (m, 3H), 7.62–7.64
(m, 1H), 7.92 (dt, J1¼8.6 Hz, J2¼1.2 Hz, 2H); 13C NMR
(CDCl3) d ꢁ0.2, 124.1, 125.0, 127.6, 128.5, 128.6, 129.0,
129.7, 134.5, 135.6, 141.1, 142.2, 142.7; IR (KBr)
. Anal. Calcd for
C15H16OS2Si: C, 59.17; H, 5.30; N, 0.00. Found: C, 58.93;
H, 5.16; N, 0.00.
n¼1360, 1230, 1060, 1030 cmꢁ1
4.3.4. 2-Bromothianthrene 5-oxide (4e). Yield 48%; mp
121–123 ꢀC (colorless crystals from dichloromethane–
hexane); 1H NMR (CDCl3) d 7.45 (dt, J1¼7.6 Hz, J2¼
1.2 Hz, 1H), 7.57 (dt, J1¼7.6 Hz, J2¼1.2 Hz, 1H), 7.61–
7.64 (m, 1H), 7.67 (dd, J1¼8.2 Hz, J2¼1.8 Hz, 1H), 7.76–
7.78 (m, 2H), 7.91–7.93 (m, 1H); 13C NMR (CDCl3)
d 124.1, 124.5, 125.8, 127.7, 128.7, 129.1, 130.0, 130.4,
142.8; IR (KBr) n¼1430, 1300, 1150, 1090, 970 cmꢁ1
.
Anal. Calcd for C19H13NS3O2Br2: C, 42.00; H, 2.41; N,
2.58. Found: C, 42.25; H, 2.14; N, 2.36. Compound 2f0:
131.5, 131.6, 140.7, 141.2; IR (KBr) n¼1420, 1060 cmꢁ1
.