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The Journal of Organic Chemistry
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66.1, 62.2, 41.4, 14.1. Anal. Calcd for C11H12O3S: C, 58.91; H, 5.39; O, 21.40; S, 14.30. Found: C,
58.58; H, 5.71; O, 21.63; S, 14.08.
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2,3-dibromopropionamide37 (IVa). Bromine (1.44 mL, 28.14 mmol) was added dropwise to a
solution of acrylamide (2.0 g, 28.14 mmol) in methanol (12 mL), at room temperature. Once
added, the reaction mixture was refluxed for 30 minutes, until decoloration occurred, then
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concentrated to dryness, affording IVa as a white solid. Yield: 6.50 g (100%). MP= 111°C. H NMR
(300 MHz, CDCl3): δ= 6.12 (bs, 1H), 6.00 (bs, 1H), 4.49 (dd, J = 8.5, 4.6 Hz, 1H), 3.95 (dd, J = 10.4,
8.5 Hz, 1H), 3.81 ppm (dd, J = 10.4, 4.6 Hz, 1H). Anal. Calcd for C3H5Br2NO: C, 15.61; H, 2.18; Br,
69.22; N, 6.07; O, 6.93. Found: C, 15.75; H, 2.42; Br, 69.01; N, 6.13; O, 6.69.
2-bromoacrylamide38 (Va). TEA (2.41 mL, 17.32 mmol) was added dropwise to a solution of IVa
(4.0 g, 17.32 mmol) in diethyl ether (40 mL), at room temperature. Once added, the reaction
mixture was refluxed for 80 hrs, the resulting suspension was filtered and the filtrate concentrated
to dryness, affording Va as a yellowish wax. Yield: 2.35 g (90%).1H NMR (300 MHz, CDCl3): δ= 6.96
(s, 1H), 6.52 (bs, 1H), 6.06 ppm (s, 1H), 5.90 (bs, 1H). Anal. Calcd for C3H4BrNO: C, 24.03; H, 2.69;
Br, 53.28; N, 9.34; O, 10.67. Found: C, 24.14; H, 2.92; Br, 53.03; N, 9.07; O, 10.84.
General procedure for 1,4-benzoxathian-2-carboxamide (5) or 1,4-benzoxathian-3-carboxamide
(6): 5 and 4 were accomplished starting from IVa (0.20 g, 0.88 mmol) and 1,2-mercaptophenol
(0.11 g, 0.88 mmol), following the same procedure described for 1 and 2, and purifying the
products by flash chromatography on silica gel, using cyclohexane/ethyl acetate 1/1 as elution
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solvent. The ratio between the two regioisomers was quantified by H NMR data; global yield:
0.012 g (7%) to 0.13 g (75%), depending on the solvent used.
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1,4-benzoxathian-2-carboxamide (5): yellow oil, tr (Method C): 7.6 min. H NMR (300 MHz,
CDCl3): δ= 7.12–6.97 (m, 2H), 6.89 (m, 2H), 6.61 (bs, 1H), 6.39 (bs, 1H), 4.73 (dd, J = 8.4, 2.5 Hz,
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1H), 3.36 (dd, J = 13.2, 2.5 Hz, 1H), 3.19 ppm (dd, J = 13.2, 8.4 Hz, 1H). C NMR (75 MHz, CDCl3):
δ= 171.3, 149.9, 127.8, 126.1, 122.4, 118.2, 117.9, 74.4, 27.1. Anal. Calcd for C9H9NO2S: C, 55.37;
H, 4.65; N, 7.17; O, 16.39; S, 16.42. Found: C, 55.61; H, 4.58; N, 6.97; O, 16.59; S, 16.25.
1,4-benzoxathian-3-carboxamide (6): white solid, MP:124°C, tr (Method C): 6.4 min. 1H NMR (300
MHz, CDCl3): δ= 7.05 (m, 2H), 6.91 (t, J = 8.2 Hz, 2H), 6.81 (bs, 1H), 6.24 (bs, 1H), 4.91 (dd, J = 11.4,
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3.3 Hz, 1H), 4.21 (dd, J = 11.4, 2.0 Hz, 1H), 3.89 ppm (dd, J = 3.3, 2.0 Hz, 1H). C NMR (75 MHz,
CDCl3): δ= 171.1, 151.6, 127.0, 126.3, 122.4, 119.0, 115.1, 66.0, 42.6. Anal. Calcd for C9H9NO2S: C,
55.37; H, 4.65; N, 7.17; O, 16.39; S, 16.42. Found: C, 55.65; H, 4.51; N, 7.07; O, 16.50; S, 16.27.
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