E
C. Li et al.
Paper
Synthesis
Cu(OTf)2 (0.10 mmol) in DCE/DMSO (5:1, 2.0 mL). To this was added
70% aq TBHP (6.0 equiv) at r.t. The rubber septum was then replaced
by a Teflon-coated screw cap, and the reaction vessel placed in an oil
bath at 90 °C for 24 or 36 h. When the reaction was complete, it was
cooled to r.t. and monitored by TLC. To the resulting solution was add-
ed 98% hydrazine hydrate (0.5 or 1.0 mL), K2CO3 (3.0 mmol), and EtOH
(2.0 mL), the mixture was stirred for 5 min and then poured into 10%
HCl (15 mL); the mixture was extracted with EtOAc (2 ×). The com-
bined organic layers were dried (anhyd Na2SO4) and the solvents were
removed in vacuo. The residue was purified by flash chromatography
(silica gel, petroleum ether/EtOAc 20:1) to give the product.
2-(p-Tolyl)benzothiazole (3g)10b
White solid; yield: 166 mg (74%); mp 73–74 °C.
1H NMR (500 MHz, CDCl3): δ = 8.11 (d, J = 8.0 Hz, 1 H), 8.01 (d, J = 8.0
Hz, 2 H), 7.88 (d, J = 8.0 Hz, 1 H), 7.51 (t, J = 7.0 Hz, 1 H), 7.38 (t, J = 7.0
Hz, 1 H), 7.30 (d, J = 8.0 Hz, 2 H), 2.43 (s, 3 H).
13C NMR (125 MHz, CDCl3): δ = 168.3, 154.2, 141.4, 135.0, 131.0,
129.8, 127.5, 126.3, 125.1, 123.1, 21.6.
2-(m-Tolyl)benzothiazole (3h)10c
White solid; yield: 157 mg (70%); mp 86–87 °C.
1H NMR (500 MHz, CDCl3): δ = 8.14 (d, J = 8.5 Hz, 1 H), 7.98 (s, 1 H),
7.91–7.86 (m, 2 H), 7.52 (dt, J = 8.0, 1.0 Hz, 1 H), 7.38 (t, J = 7.5 Hz, 2
H), 7.29 (d, J = 8.0 Hz, 1 H), 2.46 (s, 3 H).
2-Phenylbenzothiazole (3a)17
White solid; yield: 150 mg (71%); mp 109–110 °C.
1H NMR (500 MHz, CDCl3): δ = 8.14–8.10 (m, 3 H), 7.85 (d, J = 8.0 Hz, 1
H), 7.51–7.46 (m, 4 H), 7.35 (d, J = 7.5 Hz, 1 H).
13C NMR (125 MHz, CDCl3): δ = 168.3, 154.2, 138.8, 135.1, 133.6,
131.8, 128.9, 128.0, 126.3, 125.2, 124.9, 123.2, 121.7, 21.4.
13C NMR (125 MHz, CDCl3): δ = 168.1, 154.2, 135.2, 133.7, 131.0,
129.1, 127.6, 126.4, 125.2, 123.3, 121.7.
2-(o-Tolyl)benzothiazole (3i)10b
Pale yellow oil; yield: 162 mg (72%).
2-(4-Chlorophenyl)benzothiazole (3b)10b
1H NMR (500 MHz, CDCl3): δ = 8.19 (d, J = 8.0 Hz, 1 H), 7.94 (d, J = 8.0
Hz, 1 H), 7.83 (d, J = 8.0 Hz, 1 H), 7.54 (dt, J = 8.0, 1.0 Hz, 1 H), 7.45–
7.40 (m, 2 H), 7.38–7.33 (m, 1 H), 2.74 (s, 3 H).
13C NMR (125 MHz, CDCl3): δ = 168.1, 160.8, 153.9, 137.3, 135.7,
133.2, 131.7, 130.7, 130.1, 126.2, 125.2, 123.5, 121.5, 21.5.
White solid; yield: 189 mg (77%); mp 111–112 °C.
1H NMR (500 MHz, CDCl3): δ = 8.05 (d, J = 8.0 Hz, 1 H), 7.95 (d, J = 8.5
Hz, 2 H), 7.82 (d, J = 8.0 Hz, 1 H), 7.47 (t, J = 7.0 Hz, 1 H), 7.39 (d, J = 8.5
Hz, 2 H), 7.38 (t, J = 7.0 Hz, 1 H).
13C NMR (125 MHz, CDCl3): δ = 166.6, 154.1, 137.0, 135.1, 132.1,
129.2, 128.7, 126.5, 125.4, 123.3, 121.7.
2-(4-Isopropylphenyl)benzothiazole (3j)19
White solid; yield: 99 mg (39%); mp 77–78 °C.
2-(3-Chlorophenyl)benzothiazole (3c)10b
1H NMR (500 MHz, CDCl3): δ = 8.13 (d, J = 8.0 Hz, 1 H), 8.06 (d, J = 8.5
Hz, 2 H), 7.88 (d, J = 7.5 Hz, 1 H), 7.51 (t, J = 7.5 Hz, 1 H), 7.39–7.36 (m,
3 H), 3.04–2.95 (m, 1 H), 1.35 (d, J = 7.0 Hz, 6 H).
White solid; yield: 191 mg (78%); mp 93–94 °C.
1H NMR (500 MHz, CDCl3): δ = 7.89–7.84 (m, 2 H), 7.50–7.47 (m, 2 H),
7.43–7.41 (m, 1 H), 7.39–7.37 (m, 1 H), 7.36–7.34 (m, 2 H).
13C NMR (125 MHz, CDCl3): δ = 168.2, 154.3, 152.3, 135.0, 131.4,
13C NMR (125 MHz, CDCl3): δ = 166.2, 153.9, 135.2, 135.1, 135.0,
127.7, 127.2, 126.3, 125.0, 123.1, 121.6, 34.2, 23.9.
130.8, 130.2, 127.4, 126.5, 125.7, 125.6, 123.4, 121.7.
2-(4-tert-Butylphenyl)benzothiazole (3k)10c
2-(2-Chlorophenyl)benzothiazole (3d)10c
White solid; yield: 137 mg (52%); mp 92–93 °C.
1H NMR (500 MHz, CDCl3): δ = 8.13 (d, J = 8.5 Hz, 1 H), 8.07 (d, J = 8.5
Hz, 2 H), 7.87 (d, J = 8.0 Hz, 1 H), 7.54–7.49 (m, 3 H), 7.37 (t, J = 7.5 Hz,
1 H), 1.40 (s, 9 H).
White solid; yield: 135 mg (55%); mp 83–84 °C.
1H NMR (500 MHz, CDCl3): δ = 8.23 (dd, J = 7.5, 2.0 Hz, 1 H), 8.16 (d, J =
8.5 Hz, 1 H), 7.88 (d, J = 8.0 Hz, 1 H), 7.51–7.46 (m, 2 H), 7.39–7.35 (m,
1 H), 7.34–7.29 (m, 2 H).
13C NMR (125 MHz, CDCl3): δ = 168.1, 154.5, 154.3, 135.1, 131.0,
13C NMR (125 MHz, CDCl3): δ = 164.1, 152.5, 136.2, 132.7, 132.2,
127.4, 126.3, 126.0, 125.0, 123.2, 121.6, 35.0, 31.3.
131.8, 131.1, 130.8, 127.1, 126.3, 125.5, 123.5, 121.4.
2-(2-Methoxyphenyl)benzothiazole (3l)10b
2-(4-Fluorophenyl)benzothiazole (3e)10b
White solid; yield: 132 mg (55%); mp 102–103 °C.
1H NMR (500 MHz, CDCl3): δ = 8.63 (dd, J = 7.5, 1.5 Hz, 1 H), 8.18 (d, J =
8.0 Hz, 1 H), 7.93 (d, J = 8.0 Hz, 1 H), 7.53–7.50 (m, 1 H), 7.42–7.36 (m,
2 H), 7.14 (t, J = 7.0 Hz, 1 H), 6.95 (d, J = 8.5 Hz, 1 H), 3.94 (s, 3 H).
White solid; yield: 131 mg (57%); mp 87–88 °C.
1H NMR (500 MHz, CDCl3): δ = 8.05 (d, J = 8.0 Hz, 1 H), 8.03–8.00 (m, 2
H), 7.81 (d, J = 8.0 Hz, 1 H), 7.48–7.46 (m, 1 H), 7.35–7.32 (m, 1 H),
7.11 (dt, J = 8.5, 6.5, 2.0 Hz, 2 H).
13C NMR (125 MHz, CDCl3): δ = 163.2, 157.3, 152.3, 136.3, 131.9,
13C NMR (125 MHz, CDCl3): δ = 166.6, 165.4, 163.4, 154.1, 135.1,
129.5, 125.9, 124.7, 122.8, 122.3, 121.3, 121.1, 111.7, 55.6.
129.9, 129.9, 129.5, 129.4, 126.4, 125.2, 123.2, 121.6, 116.2, 116.0.
2-(4-Methoxyphenyl)benzothiazole (3m)18
2-(4-Bromophenyl)benzothiazole (3f)18
White solid; yield: 147 mg (61%); mp 125–126 °C.
1H NMR (500 MHz, CDCl3): δ = 8.05 (d, J = 8.0 Hz, 1 H), 7.99 (d, J = 8.5
Hz, 2 H), 7.79 (d, J = 8.0 Hz, 1 H), 7.45 (t, J = 7.0 Hz, 1 H), 7.30 (t, J = 7.0
Hz, 1 H), 7.38 (d, J = 8.5 Hz, 2 H), 3.76 (s, 3 H).
White solid; yield: 197 mg (68%); mp 115–117 °C.
1H NMR (500 MHz, CDCl3): δ = 8.05 (d, J = 8.0 Hz, 1 H), 7.86 (d, J = 8.5
Hz, 2 H), 7.80 (d, J = 8.0 Hz, 1 H), 7.53 (d, J = 7.5 Hz, 2 H), 7.47 (t, J = 7.0
Hz, 1 H), 7.35 (t, J = 7.0 Hz, 1 H).
13C NMR (125 MHz, CDCl3): δ = 167.8, 161.9, 154.3, 134.9, 129.1,
13C NMR (125 MHz, CDCl3): δ = 166.6, 154.1, 135.1, 132.5, 132.2,
126.4, 126.2, 124.8, 122.8, 121.5, 114.3, 55.4.
128.8, 126.5, 125.4, 123.3, 121.7.
© Georg Thieme Verlag Stuttgart · New York — Synthesis 2017, 49, A–G