5222
T. K. Pradhan et al. / Tetrahedron 60 (2004) 5215–5224
mass, difficult to separate from the unreacted starting
material was obtained. But its formation was confirmed
from IR and 1H NMR and was sufficiently pure for the next
step; nmax (Neat) 3226, 1623 cm21; dH (300 MHz, CDCl3)
7.41–7.31 (2H, m), 6.72 (1H, dd, J¼7.7, 7.8 Hz), 3.63 (2H,
s, SCH2), 3.44 (4H, m, CH2CH3), 1.15 (6H, t, J¼6.9 Hz,
CH2CH3).
petroleum (1:8)], yield 0.33 g, 83%, mp 35–39 8C. [Found:
C, 58.78; H, 7.75; N, 3.38. C20H31NO2S2Si requires C,
58.63; H, 7.63; N, 3.42%]; nmax (Neat) 3307, 1641.3 cm21
;
dH (300 MHz, CDCl3) 7.72 (1H, s), 7.38 (1H, d, J¼8.6 Hz),
7.31 (1H, d, J¼8.6 Hz), 3.61 (2H, s, SCH2), 3.04 (2H, q,
J¼7.2 Hz, NCH2), 3.23 (2H, q, J¼7.2 Hz, NCH2), 1.69–
1.15 (6H, m, CH2CH3), 0.95 (9H, s, CCH3), 0.33 (6H, s,
SiCH3); dC (75 MHz, CDCl3) 170.2, 155.8, 147.9, 138.5,
133.0, 132.3, 130.2, 113.8, 112.3, 42.8, 42.1, 40.8, 26.8,
17.3, 14.5, 13.2, 24.5.
4.1.16. 2-(N,N-Diethyl-1-acetamido-2-hydroxyphenyl-3-
)-1,3-dioxane (3d). Prepared by the same procedure from
2d (0.33 g, 1 mmol), s-BuLi (2 M, 1 mL, 2 mmol) in THF
(8 mL), TMEDA (0.3 mL, 2 mmol). Purified by column
chromatography over alumina; [eluent: ethyl acetate–
petroleum (1:3)], yield 0.23 g, 72%, Crystallised from
ether, mp 76–77 8C. [Found: C, 59.04; H, 7.32; N, 4.42.
C16H23NO4S requires 59.05; H, 7.12; N, 4.30%]; nmax (KBr)
3072, 1622 cm21; dH (300 MHz, CDCl3) 9.82 (1H, s, OH),
7.54–7.45 (2H, m), 6.84–6.79 (1H, m), 5.90 (1H, s,
OCHO), 4.26–4.20 (2H, m, OCH2CH2), 4.05–3.96 (2H, m,
OCH2CH2), 3.60 (2H, s, SCH2), 3.33 (2H, q, J¼7.1 Hz,
CH2CH3), 3.21 (2H, q, J¼7.1 Hz, CH2CH3), 2.28–2.16
(1H, m, CH2CH2CH2), 1.45–1.40 (1H, m, CH2CH2CH2),
1.20–1.08 (6H, m, CH2CH3); dC (75 MHz, CDCl3) 169.1,
156.1, 136.9, 129.1, 125.7, 119.7, 98.0, 67.4, 42.3, 41.3,
39.1, 25.7, 14.0, 12.7.
4.1.20. N,N-Diethyl-2-(3-hydroxybenzo[b]thienyl)thio-
acetamide (3h). Prepared in the same way from 2h (0.3 g,
1 mmol), s-BuLi [2 M (1 mL, 2 mmol)], THF (10 mL) using
TMEDA (0.3 mL, 2 mmol). Purified by column chroma-
tography [eluent: ethyl acetate–petroleum (3:17)], gummy
liquid, yield 0.23 g, 78%. [Found: C, 56.89; H, 5.58; N,
4.48. C14H17NO2S2 requires C, 56.92; H, 5.80; N, 4.74%];
n
max (Neat) 3130, 1605 cm21; dH (300 MHz, CDCl3) 10.74
(1H, s, OH), 7.76–7.72 (1H, m), 7.55–7.52 (1H, m), 7.25–
7.22 (2H, m), 3.49 (2H, s, SCH2), 3.28 (2H, q, J¼7.2 Hz,
NCH2), 3.12 (2H, q, J¼7.2 Hz, NCH2), 1.05–0.97 (6H, m,
CH2CH3); dC (75 MHz, CDCl3) 169.5, 154.7, 138.4, 135.5,
132.1, 124.6, 123.7, 122.1, 121.9, 42.1, 41.8, 40.6, 13.9,
12.7.
4.1.17. N,N-Diethyl-1-hydroy naphthyl-2-thioacetamide
(3e). Prepared in the same way from 2e (0.29 g, 1 mmol),
s-BuLi (2 M, 1 mL, 2 mmol) in THF (8 mL), TMEDA
(0.3 mL, 2 mmol). Purified by column chromatography
[eluent: ethyl acetate–petroleum ether (1:7)], crystallised
from ether–petroleum ether, yield 0.26 g, 92%, mp 88–
90 8C. [Found: C, 66.32; H, 6.48; N, 4.89. C16H19NO2S
requires C, 66.40; H, 6.62; N, 4.84%]; nmax (KBr) 3049,
1624 cm21; dH (300 MHz, CDCl3) 10.63 (1H, s, OH), 8.36
(1H, m), 7.71 (1H, m), 7.51–7.43 (3H, m), 7.25 (1H, d,
J¼8.4 Hz), 3.63 (2H, s, SCH2), 3.36 (2H, q, J¼7.2 Hz,
NCH2), 3.18 (2H, q, J¼7.2 Hz, NCH2), 1.13–1.07 (6H, m,
CH2CH3); dC (75 MHz, CDCl3) 170.1, 157.3, 135.9, 133.4,
127.8, 126.6, 125.7, 125.6, 124.0, 119.7, 112.0, 42.8, 41.1,
40.5, 14.5, 13.2.
4.1.21. N,N-Diethyl-2-hydroxy-3-t-butyldimethylsilyl-
phenyl thioacetamide (3i). Prepared in the same way
from 2i (0.35 g, 1 mmol), s-BuLi [2 M (1 mL, 2 mmol) in
THF (8 mL), TMEDA (0.3 mL, 2 mmol). Purified by
column chromatography [eluent: ethyl acetate–petroleum
(1:5)], mp 30–33 8C, yield 0.22 g, 64%. [Found: C, 61.34;
H, 8.92; N, 3.88. C18H31NO2SSi requires C, 61.14; H, 8.84;
N, 3.96%]; nmax (Neat) 3325, 1595 cm21; dH (300 MHz,
CDCl3) 7.38 (2 H, m), 7.28 (1H, d, J¼8.0 Hz), 3.61 (2H, s,
SCH2), 3.38 (2H, q, J¼7.1 Hz, NCH2), 3.21 (2H, q,
J¼7.1 Hz, NCH2), 1.15–1.09 (6H, m, CH2CH3), 0.95
(9H, s, CCH3), 0.33 (6H, s, SiMe); dC (75 MHz, CDCl3)
170.2, 155.8, 147.9, 133.0, 132.3, 130.3, 113.8, 112.3, 42.8,
42.1, 40.0, 26.8, 17.3, 14.5, 13.2, 24.59.
4.1.22. N,N-Diethyl-2-hydroxy-3-methylphenylthio-
acetamide (3j). Prepared in the same way from 2j
(0.25 g, 1 mmol), s-BuLi [2 M (0.5 mL, 1 mmol) in THF
(8 mL), TMEDA (0.15 mL, 1 mmol). Purified by column
chromatography [eluent: ethyl acetate–petroleum (1:5)],
mp 30–35 8C, yield 0.16 g, 63%. [Found: C, 61.81; H,
7.38; N, 5.73. C13H19NO2S requires C, 61.63; H, 7.56; N,
5.53%; nmax (Neat) 3168, 1620 cm21; dH (300 MHz,
CDCl3) 10.19 (1H, s, OH), 7.18–7.04 (1H, m), 6.84
(1H, d, J¼7.4 Hz), 6.77–6.72 (1H, m), 3.63 (2H, s,
SCH2), 3.43–3.29 (4H, m, NCH2), 2.34 (3H, s, ArCH3),
1.26–1.03 (6H, m, CH2CH3); dC (75 MHz, CDCl3) 173.6,
159.3, 133.3, 132.4, 123.7, 121.6, 121.3, 54.3, 45.9, 44.3,
17.5, 17.1, 15.2.
4.1.18. N,N-Diethyl-1-hydroxy-6-methoxy naphthyl-2-
thioacetamide (3f). Prepared in the same way from 2f
(0.5 g, 1.6 mmol), TMEDA (0.58 mL, 4 mmol), THF
(8 mL) and s-BuLi (2.4 mL of 1.6 M solution, 4 mmol).
Purified by column chromatography [eluent: ethyl acetate–
petroleum ether (3:17)], liquid oil, yield 0.45 g, 90%.
[Found: C, 64.06; H, 6.66; N, 4.29. C17H21O3NS requires C,
63.90; H, 6.58; N, 4.38%]; nmax (Neat) 3062, 1730 cm21; dH
(300 MHz, CDCl3) 8.2 (1H, d, J¼9.1 Hz), 7.38 (1H, d,
J¼8.6 Hz), 7.09 (1H, d, J¼8.6 Hz), 7.03 (1H, dd, J¼2.4,
9.1 Hz), 6.96 (1H, d, J¼2.4 Hz), 3.83 (3H, s, OMe), 3.56
(2H, s, SCH2), 3.50–3.15 (4H, m, CH2CH3), 1.27–1.03
(6H, m, CH2CH3); dC (75 MHz, CDCl3) 159.3, 158.0,
137.5, 134.2, 133.0, 121.2, 118.6, 117.9, 105.9, 55.6, 42.8,
42.1, 40.6, 14.6, 13.2.
4.1.23. General procedure of synthesis of oxathiin-2-
ones. 8-Methoxy benz[1,4]oxathiin-2-one (4a). The
hydroxy compound 3a (0.25 g, 9.3 mmol) was heated with
7 mL of glacial acetic acid for 18 h under magnetic stirring
condition. Cooling, the reaction mixture was extracted with
dichloromethane (2£20 mL). The organic layer was washed
with water, dried (Na2SO4). Removal of solvent afforded the
4.1.19. N,N-Diethyl-5-(2-t-butyldimethylsilyl-4-hydroxy-
benzo[b]thienyl) thioacetamide (3g). Prepared in the same
way from 2g (0.4 g, 1 mmol), s-BuLi [2 M (1 mL,
2 mmol)], THF (10 mL) using TMEDA (0.3 mL, 2 mmol).
Purified by column chromatography [eluent: ethyl acetate–