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Synlett 2009(8): 1336-1340  
DOI: 10.1055/s-0028-1216725
LETTER
© Georg Thieme Verlag Stuttgart ˙ New York

Facile Preparation of 3,4-Dihydro-2,1-benzothiazine 2,2-Dioxides and Related Reaction with 1,3-Diiodo-5,5-dimethylhydantoin under Photochemical Conditions

Atsushi Moroda, Shusuke Furuyama, Hideo Togo*
Graduate School of Science, Chiba University, Yayoi-cho 1-33, Inage-ku, Chiba 263-8522, Japan
Fax: +81(43)2902792; e-Mail: togo@faculty.chiba-u.jp;
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Publication History

Received 2 February 2009
Publication Date:
17 April 2009 (online)

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Abstract

3,4-Dihydro-2,1-benzothiazine 2,2-dioxides were easily obtained in good yields by the reaction of N-methyl 2-arylethanesulfonamides with 1,3-diiodo-5,5-dimethylhydantoin (DIH) under irradiation with a tungsten lamp. When N-benzyl 2-phenylethanesulfonamide was treated with DIH under the same conditions, the corresponding N-benzyl 3,4-dihydro-2,1-benzothiazine 2,2-dioxide was obtained in good yield, and the N-benzyl group was easily removed by the treatment with hydrogen in the presence of Pd(OH)2. On the other hand, treatment of N-3-arylpropyl trifluoromethanesulfonamides with DIH under irradiation with a tungsten lamp provided corresponding N-trifluoromethanesulfonyl-1,2,3,4-tetra-hydroquinolines in good yields.

Key words

3,4-dihydro-2,1-benzothiazine 2,2-dioxide - 1,3-diiodo-5,5-dimethylhydantoin - 1,2,3,4-tetrahydroquinoline - tungsten lamp - irradiation - sulfonamidyl radical

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General Procedure for the Conversion of N -Methyl- or N -Benzyl 2-Arylethanesulfonamides into the Corresponding N -Methyl-3,4-dihydro-2,1-benzothiazine 2,2-dioxides with DIH
1,3-Diiodo-5,5-dimethylhydantoin (0.6 mmol, 228 mg) was added to a soln of N-methyl 2-arylethanesulfonamide (0.5 mmol) in EtOAc (5 mL). The mixture was irradiated with a tungsten lamp (500 W) at 30-40 ˚C for 4 h under an argon atmosphere. After the reaction, the mixture was poured into sat. aq Na2SO3 soln and extracted with CHCl3 three times. Then, the organic layer was dried over Na2SO4. After removal of the solvent under reduced pressure, the residue was subjected to preparative TLC on SiO2 using a mixture of hexane, EtOAc, and CHCl3 (6:3:1) as eluent.
Typical Procedure for the Reduction of N -Benzyl-3,4-dihydro-2,1-benzothiazine 2,2-dioxide
Palladium hydroxide (20 wt% Pd/C, 200 mg) was added to a soln of N-benzyl-3,4-dihydro-2,1-benzothiazine 2,2-dioxide (1 mmol, 273.4 mg) in EtOAc (4 mL) and EtOH (4 mL). The mixture was stirred at r.t. for 48 h under H2 atmosphere. After the reaction, the mixture was poured into CHCl3 and washed with H2O. The organic layer was dried over Na2SO4. After removal of the solvent under reduced pressure, the residue was subjected to preparative TLC on SiO2 using a mixture of hexane and EtOAc (2:1) as eluent.
N -Methyl-3,4-dihydro-2,1-benzothiazine 2,2-Dioxide Mp 77.0-79.0 ˚C. IR (KBr): 1580, 1490, 1330, 1170 cm-¹. ¹H NMR (400 MHz, CDCl3): δ = 3.30 (s, 3 H), 3.32 (t, J = 6.9 Hz, 2 H), 3.43 (t, J = 6.9 Hz, 2 H), 6.96 (dd, J = 8.0, 1.0 Hz, 1 H), 7.05 (td, J = 7.6, 1.0 Hz, 1 H), 7.16 (dd, J = 7.6, 1.2 Hz, 1 H), 7.27 (m, 1 H). ¹³C NMR (125 MHz, CDCl3): δ = 27.90 (s), 31.97 (p), 45.55 (s), 117.47 (t), 122.82 (q), 123.14 (t), 127.88 (t), 129.30 (t), 141.14 (q). MS (EI): m/z = 197 [M+]. Anal. Calcd (%) for C9H11NO2S: C, 54.80; H, 5.62; N, 7.10. Found: C, 54.74; H, 5.52; N, 7.07.
N -Methyl-7-methyl-3,4-dihydro-2,1-benzothiazine 2,2-Dioxide Mp 78.0-79.0 ˚C. IR (paraffin oil): 1330, 1200, 1159 cm-¹. ¹H NMR (400 MHz, CDCl3): δ = 2.34 (s, 3 H), 3.29 (s, 3 H), 3.32 (t, J = 7.0 Hz, 2 H), 3.40 (t, J = 7.0 Hz, 2 H), 6.77 (s, 1 H), 6.86 (d, J = 7.8 Hz, 1 H), 7.04 (d, J = 7.8 Hz, 1 H). ¹³C NMR (100 MHz, CDCl3): δ = 21.27 (p), 27.50 (s), 32.15 (p), 45.55 (s), 118.20 (t), 119.78 (q), 124.02 (t), 129.16 (t), 137.81 (q), 140.92 (q). HRMS-FAB: m/z calcd for C10H13NO2S: 211.0667 [M]; found: 211.0667 [M+].
N -Methyl-7-fluoro-3,4-dihydro-2,1-benzothiazine 2,2-Dioxide Mp 67.0-68.0 ˚C. IR (KBr): 1620, 1590, 1510, 1320, 1300, 1210, 1170, 1140 cm-¹. ¹H NMR (400 MHz, CDCl3): δ = 3.28 (s, 3 H), 3.34 (ddd, J = 7.5, 6.3, 1.4 Hz, 2 H), 3.43 (ddd, J = 7.5, 6.3, 1.4 Hz, 2 H), 6.66 (dd, J = 10.6, 2.4 Hz, 1 H), 6.75 (td, J = 8.2, 2.4 Hz, 1 H), 7.09-7.14 (m, 1 H). ¹³C NMR (100 MHz, CDCl3): δ = 27.36 (s), 31.21 (p), 45.68 (s), 104.34 (t, J C-F = 26.5 Hz), 109.68 (t, J C-F = 21.5 Hz), 118.05 (q, J C-F = 4.2 Hz), 130.67 (t, J C-F = 9.1 Hz), 142.43 (q, J C-F = 9.9 Hz), 162.30 (q, J C-F = 245.6 Hz). MS (EI): m/z = 215 [M+]. Anal. Calcd (%) for C9H10FNO2S: C, 50.22; H, 4.68; N, 6.51. Found: C, 50.03; H, 4.70; N, 6.50.
N -Methyl-7-chloro-3,4-dihydro-2,1-benzothiazine 2,2-Dioxide Mp 93.0-94.0 ˚C. IR (KBr): 1600, 1490, 1330, 1160 cm-¹. ¹H NMR (400 MHz, CDCl3): δ = 3.29 (s, 3 H), 3.34 (t, J = 7.3 Hz, 2 H), 3.43 (t, J = 7.3 Hz, 2 H), 6.93 (d, J = 1.9 Hz, 1 H), 7.02 (dd, J = 8.0, 1.9 Hz, 1 H), 7.09 (d, J = 8.0 Hz, 1 H). ¹³C NMR (100 MHz, CDCl3): δ =  27.53 (s), 31.42 (p), 45.52 (s), 117.10 (t), 120.89 (q), 122.96 (t), 130.45 (t), 133.65 (q), 142.11 (q). MS (EI): m/z = 231 [M+]. Anal. Calcd (%) for C9H10ClNO2S: C, 46.65; H, 4.35; N, 6.05. Found: C, 46.60; H, 4.29; N, 5.94.
N -Methyl-7-bromo-3,4-dihydro-2,1-benzothiazine 2,2-Dioxide Mp 103-105 ˚C. IR (paraffin oil): 1330, 1300, 1200, 1160, 914 cm-¹. ¹H NMR (400 MHz, CDCl3): δ = 3.29 (s, 3 H), 3.32-3.37 (m, 2 H), 3.38-3.43 (m, 2 H), 7.03 (d, J = 8.0 Hz, 1 H), 7.08 (d, J = 1.9 Hz, 1 H), 7.17 (dd, J = 8.0, 1.9 Hz, 1 H). ¹³C NMR (100 MHz, CDCl3): δ = 27.68 (s), 31.60 (p), 45.54 (s), 120.07 (t), 121.46 (q), 121.54 (q), 125.99 (t), 130.80 (t), 142.35 (q). HRMS-FAB: m/z calcd for C9H10NO2SBr: 274.9616 [M]; found: 274.9598 [M+].
N -Benzyl-3,4-dihydro-2,1-benzothiazine 2,2-Dioxide Mp 71.0-73.0 ˚C. IR (KBr): 1600, 1580, 1500, 1460, 1330, 1160 cm-¹. ¹H NMR (400 MHz, CDCl3): δ = 3.25 (t, J = 6.9 Hz, 2 H), 3.44 (t, J = 6.9 Hz, 2 H), 5.00 (s, 2 H), 6.88 (d, J = 8.2 Hz, 1 H), 7.01 (t, J = 7.5, 1.2 Hz, 1 H), 7.10-7.16 (m, 2 H), 7.23-7.37 (m, 5 H). ¹³C NMR (100 MHz, CDCl3): δ = 28.16 (s), 45.92 (s), 51.11 (s), 119.09 (t), 123.05 (q), 123.46 (t), 127.09 (t), 127.63 (t), 127.81 (t), 128.79 (t), 129.51 (t), 136.57 (q), 140.26 (q). MS (EI): m/z = 273 [M+]. Anal. Calcd (%) for C15H15NO2S: C, 65.91; H, 5.53; N, 5.12. Found: C, 65.78; H, 5.53; N, 5.02.
3,4-Dihydro-2,1-benzothiazine 2,2-Dioxide Mp 150.0-152.0 ˚C. ¹H NMR (400 MHz, CDCl3): δ = 3.32 (t, J = 6.9 Hz, 2 H), 3.49 (t, J = 6.9 Hz, 2 H), 6.45 (s, 1 H), 6.75 (dd, J = 8.1, 1.1 Hz, 1 H), 7.05 (td, J = 7.5, 1.1 Hz, 1 H), 7.17-7.23 (m, 2 H).

10

General Procedure for the Conversion of N -3-Arylpropyl Trifluoromethanesulfonamides into the Corresponding N -(Trifluoromethanesulfonyl)-1,2,3,4-tetrahydroquinolines with DIH
A soln of N-3-arylpropyl trifluoromethanesulfonamide (1.0 mmol) and 1,3-diiodo-5,5-dimethylhydantoin (1.2 mmol, 455.9 mg) in DCE (15 mL) was irradiated with a tungsten lamp (500 W) for 7 h at 60 ˚C under an argon atmosphere. After the reaction, the mixture was poured into a sat. aq Na2SO3 soln and extracted with CHCl3 three times. The organic layer was dried over Na2SO4. After filtration, the solvent was removed under reduced pressure, and the residue was subjected to flash column chromatography on SiO2 using a mixture of hexane, EtOAc, and CHCl3 (1:10:1) as eluent.
N -(Trifluoromethanesulfonyl)-1,2,3,4-tetrahydro-quinoline Oil. IR (neat): 1580, 1480, 1220, 1200 cm-¹. ¹H NMR (400 MHz, CDCl3): δ = 2.11 (quin, J = 6.4 Hz, 2 H), 2.88 (t, J = 6.4 Hz, 2 H), 3.87 (t, J = 6.4 Hz, 2 H), 7.15-7.22 (m, 3 H), 7.52 (d, J = 7.7 Hz, 1 H). ¹³C NMR (100 MHz, CDCl3): δ = 23.39 (s), 26.13 (s), 47.94 (s), 120.11 (q, J C-F = 328 Hz, CF3), 123.34 (t), 126.15 (t), 126.79 (t), 129.46 (t), 130.91 (q), 135.31 (q). HRMS (EI): m/z calcd for C10H10F3NO2S: 265.0384 [M]; found: 265.0390 [M+].
N -(Trifluoromethanesulfonyl)-7-chloro-1,2,3,4-tetra-hydroquinoline
Oil. IR (neat): 1601, 1574, 1454, 1353, 1311, 1025 cm-¹. ¹H NMR (500 MHz, CDCl3): δ = 2.10 (m, 2 H), 2.85 (t, J = 6.8 Hz, 2 H), 3.86 (t, J = 6.0 Hz, 2 H), 7.08-7.15 (m, 2 H), 7.56 (s, 1 H). ¹³C NMR (125 MHz, CDCl3): δ = 23.03 (s), 25.80 (s), 47.90 (s), 119.89 (q, J C-F = 324 Hz, q, CF3), 123.34 (t), 126.30 (t), 129.08 (q), 130.45 (t), 132.14 (q), 136.08 (q)- HRMS-FAB: m/z calcd for C10H9ClF3NO2S: 298.9995 [M]; found: 299.0006 [M+].
N -(Trifluoromethanesulfonyl)-7-methyl-1,2,3,4-tetra-hydroquinoline
Oil. IR (neat): 1620, 1576, 1455, 1393, 1353, 1313 cm-¹. ¹H NMR (500 MHz, CDCl3): δ = 2.09 (m, 2 H), 2.33 (s, 3 H), 2.83 (t, J = 6.9 Hz, 2 H), 3.84 (t, J = 6.1 Hz, 2 H), 6.97 (d, J = 7.4 Hz, 1 H), 7.04 (d, J = 7.4 Hz, 1 H), 7.33 (s, 1 H). ¹³C NMR (125 MHz, CDCl3): δ = 21.18 (p), 23.44 (s), 25.69 (s), 47.98 (s), 120.00 (q, J C-F = 324 Hz, q, CF3), 123.75 (t), 127.07 (t), 127.81 (q), 129.19 (t), 135.10 (q), 136.65 (q). HRMS-FAB: m/z calcd for C11H12F3NO2S: 279.0541 [M]; found: 279.0538 [M+].
N -(Trifluoromethanesulfonyl)-7-methoxy-1,2,3,4-tetra-hydroquinoline
Oil. IR (neat): 1617, 1583, 1430, 1293, 1039 cm-¹. ¹H NMR (500 MHz, CDCl3): δ = 2.08 (m, 2 H), 2.81 (t, J = 6.9 Hz 2 H), 3.78 (s, 3 H), 3.85 (t, J = 6.0 Hz, 2 H), 6.73 (dd, J = 8.2, 2.5 Hz, 1 H), 7.05 (d, J = 8.2 Hz, 1 H), 7.12 (d, J = 2.5 Hz, 1 H). ¹³C NMR (125 MHz, CDCl3): δ = 23.37 (s), 25.47 (s), 48.11 (s), 55.44 (p), 108.55 (t), 112.72 (t), 120.00 (q, J C-F = 324 Hz, q, CF3), 122.58 (q), 130.08 (t), 135.87 (q), 158.15 (q). HRMS-FAB: m/z calcd for C11H12F3NO3S: 295.0490 [M]; found: 295.0482 [M+].
N -(Trifluoromethanesulfonyl)-7-fluoro-1,2,3,4-tetra-hydroquinoline
Oil. IR (neat): 1614, 1426, 1315, 1029 cm-¹. ¹H NMR (500 MHz, CDCl3): δ = 2.10 (m, 2 H), 2.84 (t, J = 6.9 Hz, 2 H), 3.87 (t, J = 6.0 Hz, 2 H), 6.88 (dt, J = 8.2, 2.4 Hz, 1 H), 7.11 (m, 1 H) 7.33 (dd, J = 10.7, 2.4 Hz, 1 H). ¹³C NMR (125 MHz, CDCl3): δ = 23.07 (s), 25.74 (s), 47.96 (s), 110.52 (t, J = 26 Hz), 113.28 (t, J = 21 Hz), 119.92 (q, J C-F = 323 Hz, q, CF3), 126.00 (q), 130.50 (t, J = 9 Hz), 159.86 (q), 161.81 (q). HRMS-FAB: m/z calcd for C10H9F4NO2S: 283.0290 [M]; found: 283.0280 [M+].