Facile Preparation of Thiazoles
from 1H-1-(1′-Alkynyl)-5-methyl-1,2,3-benziodoxathiole
3,3-Dioxide with Thioamides

Yoshihide Ishiwata; Hideo Togo

doi:10.1055/s-0028-1083439

LETTER

Facile Preparation of Thiazoles from 1H-1-(1′-Alkynyl)-5-methyl-1,2,3-benziodoxathiole 3,3-Dioxide with Thioamides

Yoshihide Ishiwata, Hideo Togo*
Graduate School of Science, Chiba University, Yayoi-cho 1-33, Inage-ku, Chiba 263-8522, Japan
e-Mail: togo@faculty.chiba-u.jp;

Abstract

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Abstract

Thiazoles were obtained in high yields by the reaction of 1H-1-(1′-alkynyl)-5-methyl-1,2,3-benziodoxathiole 3,3-dioxides, which were easily prepared from the reaction of 1H-1-hydroxy-5-methyl-1,2,3-benziodoxathiole 3,3-dioxide and 1-alkynes, with thioamides. Here, the co-product, potassium 2-iodo-5-methylbenzenesulfonate, was recovered quantitatively by simple filtration of the reaction mixture, and was regenerated to 1H-1-(1′-alkynyl)-5-methyl-1,2,3-benziodoxathiole 3,3-dioxides to be reused for the same preparation of thiazoles, keeping good yields.

Key words

thiazole - 1H-1-(1′-alkynyl)-5-methyl-1,2,3-benziodoxathiole 3,3-dioxide - 1-alkyne - thioamide

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References

References and Notes

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Typical Procedure for Preparation of 1 H -1-(1′-Hexynyl)-5-methyl-1,2,3-benziodoxathiole 3,3-Dioxide A mixture of 1H-1-hydroxy-5-methyl-1,2,3-benziodoxa-thiole 3,3-dioxide (5 mmol), PTSA˙H₂O (5 mmol), and 1-hexyne (25 mmol) in MeCN (40 mL) was refluxed for 20 h. After removal of the solvent to obtain an oil, a solution of the oil in CHCl₃ (200 mL) was washed with 5% NaHCO₃ (80 mL) and H₂O (3 × 50 mL), and was concentrated to a solid. Recrystallization of the solid with a mixture of CH₂Cl₂ (30 mL), Et₂O (100 mL), and hexane (60 mL) gave 1H-1-(1′-hexynyl)-5-methyl-1,2,3-benziodoxathiole 3,3-dioxide in 53% yield.
1 H -1-(1′-Hexynyl)-5-methyl-1,2,3-benziodoxathiole 3,3-Dioxide (R = n -Bu) Mp 164-166 ˚C (dec.); lit.⁷ 179-181 ˚C (dec.). IR (Nujol): 2166 cm^-¹. ^¹H NMR (400 MHz, CDCl₃, TMS): δ = 8.01(s, 1 H), 7.92 (d, J = 8.5 Hz, 1 H), 7.47 (d, J = 8.7 Hz, 1 H), 2.73 (t, J = 7.2 Hz, 2 H), 2.50 (s, 3 H), 1.61-1.74 (m, 2 H), 1.43-1.55 (m, 2 H), 0.98 (t, J = 7.4 Hz, 3 H). ^¹³C NMR (100 MHz, CDCl₃, TMS): δ = 143.7, 141.6, 135.1, 130.8, 126.8, 115.5, 105.8, 29.9, 28.5, 22.1, 20.8, 20.6, 13.5.
1 H -1-(1′-Octynyl)-5-methyl-1,2,3-benziodoxathiole 3,3-Dioxide (R = n -C ₆ H ₁₃ ) Mp 150 ˚C (dec.); lit.⁷ 152-154 ˚C (dec.). IR (Nujol): 2168 cm^-¹. ^¹H NMR (400 MHz, CDCl₃, TMS): δ = 8.04 (s, 1 H), 7.90 (d, J = 8.7 Hz, 1 H), 7.48 (dd, J = 1.6, 8.6 Hz, 1 H), 2.73 (t, J = 7.1 Hz, 2 H), 2.51 (s, 3 H), 1.64-1.74 (m, 2 H), 1.42-1.52 (m, 2 H), 1.30-1.40 (m, 4 H), 0.92 (t, J = 7.0 Hz, 3 H). ^¹³C NMR (100 MHz, CDCl₃, TMS): δ = 143.8, 141.5, 135.0, 130.8, 126.6, 115.5, 105.8, 31.1, 28.5, 28.4, 27.8, 22.4, 20.9, 20.7, 14.0.
1 H -1-(1′-Phenylethynyl)-5-methyl-1,2,3-benziodoxa-thiole 3,3-Dioxide (R = Ph) Mp 217-219 ˚C (dec.); lit.⁷ 221-223 ˚C (dec.). IR (Nujol): 2160 cm^-¹. ^¹H NMR (400 MHz, DMSO-d ₆, TMS): δ = 8.12 (d, J = 8.4, 1 H), 7.76-7.81(m, 3 H), 7.53-7.67 (m, 4 H), 2.45 (s, 3 H). ^¹³C NMR (100 MHz, DMSO-d ₆, TMS): δ = 142.6, 142.4, 135.0, 133.0, 131.6, 129.1, 129.1, 128.9, 119.4, 107.7, 107.2, 41.3, 20.2.
Typical Procedure for Preparation of Thiazoles
To a solution of thiobenzamide (0.48 mmol) in THF (2 mL) were added K₂CO₃ (0.92 mmol) and 1H-1-(1′-phenyl-ethynyl)-5-methyl-1,2,3-benziodoxathiole 3,3-dioxide (0.4 mmol). The obtained mixture was stirred at 45 ˚C overnight under argon atmosphere. After the reaction, the mixture was filtered to remove potassium 2-iodo-5-methyl-benzene-sulfonate quantitatively. After evaporation of the filtrate, the residue was chromatographed on SiO₂ (eluent: hexane-CHCl₃, 1:1) to afford pure 1,4-diphenylthiazole in 65% yield.
2,4-Diphenylthiazole Mp 91-92 ˚C; lit.^¹0 91-92 ˚C. ^¹H NMR (400 MHz, CDCl₃, TMS): δ = 7.98-8.09 (m, 4 H), 7.41-7.51 (m, 6 H), 7.35 (t, J = 7.4 Hz, 1 H).
Regeneration of Potassium 2-Iodo-5-methylbenzene-sulfonate to 1 H -1-Hydroxy-5-methyl-1,2,3-benziod-oxathiole 3,3-Dioxide Hydrogen peroxide (33%, 1.3 mL) was added dropwise to a solution of acetic anhydride (1.2 mL) at 0 ˚C. The obtained mixture was stirred overnight. After the reaction, the mixture was added dropwise to a stirred mixture of potassium
2-iodo-5-methylbenzenesulfonate (2.4 mmol) in AcOH (4 mL) and concd H₂SO₄ (1.2 mL) while keeping the temperature at 10-15 ˚C. The mixture was stirred at this temperature for 1 h and overnight at r.t. After the reaction, the precipitate was filtered to give 1H-1-hydroxy-5-methyl-1,2,3-benziodoxathiole 3,3-dioxide in 50-60% yield.
2-Phenyl-4-butylthiazole
Oil. IR(neat): 2956, 2929, 2859, 1516, 1498, 1460, 1436, 1244, 1004, 763, 689 cm^-¹. ^¹H NMR (400 MHz, CDCl₃, TMS): δ = 7.93 (dd, J = 1.4, 8.0 Hz, 2 H), 7.38-7.45 (m, 3 H), 6.86 (s, 1 H), 2.83 (t, J = 7.8 Hz, 2 H), 1.70-1.80 (m, 2 H), 1.37-1.49 (m, 2 H), 0.96 (t, J = 7.4 Hz, 3 H). ^¹³C NMR (100 MHz, CDCl₃, TMS): δ = 167.4, 158.9, 133.9, 129.7, 128.8, 126.5, 112.6, 31.4, 31.3, 22.4, 13.9. HRMS-FAB: m/z calcd for C₁₃H₁₆NS [M + H]: 218.1003; found: 218.1006.
2-Methyl-4-butylthiazole
Oil. IR(neat): 3427, 2956, 2929, 2859, 1637, 1523, 1457, 1183, 1133, 730, 560, 526 cm^-¹. ^¹H NMR (400 MHz, CDCl₃, TMS): δ = 6.69 (s, 1 H), 2.67-2.76 (m, 5 H), 1.62-1.73 (m, 2 H), 1.32-1.44 (m, 2 H), 0.93 (t, J = 7.4 Hz, 3 H).^¹³C NMR (100 MHz, CDCl₃, TMS): δ = 165.2, 157.3, 111.9, 31.4, 31.2, 22.4, 19.1, 13.9. HRMS-FAB: m/z calcd for C₈H₁₄NS [M + H]: 156.0847; found: 156.0837.
2-(4-Methylphenyl)-4-butylthiazole
Oil. IR(neat): 2955, 2928, 2859, 1509, 1457, 1246, 1007, 818, 735, 711 cm^-¹. ^¹H NMR (400 MHz, CDCl₃, TMS): δ = 7.82 (d, J = 8.2 Hz, 2 H), 7.22 (d, J = 8.0 Hz, 2 H), 6.82 (s, 1 H), 2.81 (t, J = 7.7 Hz, 2 H), 2.38 (s, 3 H), 1.69-1.79 (m, 2 H), 1.36-1.48 (m, 2 H), 0.96 (t, J = 7.4 Hz, 3 H). ^¹³C NMR (100 MHz, CDCl₃, TMS): δ = 167.6, 158.7, 139.8, 131.3, 129.5, 126.4, 112.1, 31.4, 31.3, 22.4, 21.4, 13.9. HRMS-FAB: m/z calcd for C₁₄H₁₈NS [M + H]: 232.1160; found: 232.1161.
2-(4-Methoxyphenyl)-4-butylthiazole
Oil. IR(neat): 2859 cm^-¹. ^¹H NMR (400 MHz, CDCl₃, TMS): δ = 7.87 (d, J = 8.9 Hz, 2 H), 6.94 (d, J = 9.0 Hz, 2 H), 6.79 (s, 1 H), 3.85 (s, 3 H), 2.81 (t, J = 7.7 Hz, 2 H), 1.68-1.80 (m, 2 H), 1.36-1.48 (m, 2 H), 0.96 (t, J = 7.3 Hz, 3 H). ^¹³C NMR (100 MHz, CDCl₃, TMS): δ = 167.5, 161.0, 158.7, 128.1, 127.1, 114.3, 111.8, 55.5, 31.6, 31.5, 22.6, 14.1. HRMS-FAB: m/z calcd for C₁₄H₁₈NOS [M + H]: 248.1109; found: 248.1119.
2-(4-Nitrophenyl)-4-butylthiazole
Mp 47-48 ˚C. IR (Nujol): 1522, 1345, 851 cm^-¹. ^¹H NMR (400 MHz, CDCl₃, TMS): δ = 8.29 (d, J = 8.9 Hz, 2 H), 8.11 (d, J = 9.2 Hz, 2 H), 7.03 (s, 1 H), 2.85 (t, J = 7.7 Hz, 2 H), 1.71-1.81 (m, 2 H), 1.38-1.49 (m, 2 H), 0.97 (t, J = 7.4 Hz, 3 H). ^¹³C NMR (100 MHz, CDCl₃, TMS): δ = 164.2, 160.1, 148.2, 139.4, 127.0, 124.2, 115.0, 31.3, 22.3, 13.9. HRMS-FAB: m/z calcd for C₁₃H₁₅N₂O₂S [M + H]: 263.0854; found: 263.0838.
2-Amino-4-butylthiazole Oil. IR (Nujol): 3436, 1607, 1521, 1113, 696 cm^-¹. ^¹H NMR (400 MHz, CDCl₃, TMS): δ = 6.08 (s, 1 H), 4.91 (s, 2 H), 2.53 (t, J = 7.8 Hz, 2 H), 1.56-1.68 (m, 2 H), 1.30-1.43 (m, 2 H), 0.92 (t, J = 7.4 Hz, 3 H). ^¹³C NMR (100 MHz, CDCl₃, TMS): δ = 167.3, 102.5, 102.5, 31.7, 31.2, 22.7, 14.2. HRMS-FAB: m/z calcd for C₇H₁₃N₂S [M + H]: 157.0799; found: 157.0811.
2-Phenyl-4-hexylthiazole
Oil. IR(neat): 2926, 2856, 1517, 1458, 1239, 1003, 763, 689 cm^-¹. ^¹H NMR (400 MHz, CDCl₃, TMS): δ = 7.94 (dd, J = 1.7, 7.8 Hz, 2 H), 7.36-7.47 (m, 3 H), 6.87 (s, 1 H), 1.70-1.82 (m, 2 H), 1.27-1.47 (m, 6 H), 0.89 (t, J = 7.1 Hz, 3 H). ^¹³C NMR (100 MHz, CDCl₃, TMS): δ = 167.4, 158.9, 133.9, 129.7, 128.8, 126.5, 112.6, 31.7, 31.7, 29.2, 29.0, 22.6, 14.1. HRMS-FAB: m/z calcd for C₁₅H₂₀NS [M + H]: 246.1316; found: 246.1315.
2-Methyl-4-hexylthiazole
Oil. IR(neat): 2955, 2926, 2856, 1523, 1457, 1183, 728 cm^-¹. ^¹H NMR (400 MHz, CDCl₃, TMS): δ = 6.69 (s, 1 H), 2.67-2.75 (m, 5 H), 1.62-1.75 (m, 2 H), 1.23-1.45 (m, 6 H), 0.88 (t, J = 7.0 Hz, 3 H). ^¹³C NMR (100 MHz, CDCl₃, TMS): δ = 165.2, 157.4, 111.9, 31.6, 31.6, 29.2, 29.0, 22.6, 19.1, 14.1. HRMS-FAB: m/z calcd for C₁₀H₁₈NS [M + H]: 184.1160; found: 184.1167.
2-(4-Methylphenyl)-4-hexylthiazole
Oil. IR(neat): 2926, 2856, 1509, 1457, 1247, 1005, 817, 711 cm^-¹. ^¹H NMR (400 MHz, CDCl₃, TMS): δ = 7.82 (d, J = 8.3 Hz, 2 H), 7.22 (d, J = 7.8 Hz, 2 H), 6.82 (s, 1 H), 2.80 (t, J = 7.6 Hz, 2 H), 2.38 (s, 3 H), 1.70-1.81 (m, 2 H), 1.27-1.46 (m, 6 H), 0.89 (t, J = 7.1 Hz, 3 H). ^¹³C NMR (100 MHz, CDCl₃, TMS): δ = 167.6, 158.7, 139.9, 131.3, 129.5, 126.4, 112.1, 31.7, 31.7, 29.2, 29.0, 22.6, 21.4, 14.1. HRMS-FAB: m/z calcd for C₁₆H₂₂NS [M + H]: 260.1473; found: 260.1493.
2-(4-Methoxyphenyl)-4-hexylthiazole
Oil. IR(neat): 2855 cm^-¹. ^¹H NMR (400 MHz, CDCl₃, TMS): δ = 7.87 (d, J = 9.0 Hz, 2 H), 6.94 (d, J = 8.8 Hz, 2 H), 6.79 (s, 1 H), 3.85 (s, 3 H), 2.80 (t, J = 7.8 Hz, 2 H), 1.69-1.80 (m, 2 H), 1.25-1.45 (m, 6 H), 0.89 (t, J = 6.9 Hz, 3 H). ^¹³C NMR (100 MHz, CDCl₃, TMS): δ = 160.8, 158.6, 134.0, 127.9, 126.9, 114.1, 111.7, 55.4, 31.7, 31.7, 29.2, 29.0, 22.6, 14.1. HRMS-FAB: m/z calcd for C₁₆H₂₂NOS [M + H]: 276.1422; found: 276.1401.
2-(4-Nitrophenyl)-4-hexylthiazole
Mp 45-46 ˚C. IR (Nujol): 1523, 1339, 852 cm^-¹. ^¹H NMR (400 MHz, CDCl₃, TMS): δ = 8.28 (d, J = 8.8 Hz, 2 H), 8.10 (d, J = 9.1 Hz, 2 H), 7.03 (s, 1 H), 2.84 (t, J = 7.8 Hz, 2 H), 1.72-1.81 (m, 2 H), 1.30-1.45 (m, 6 H), 0.90 (t, J = 7.8 Hz, 3 H). ^¹³C NMR (100 MHz, CDCl₃, TMS): δ = 164.2, 160.1, 148.2, 139.4, 127.0, 124.2, 115.0, 31.6, 31.6, 29.1, 28.9, 22.6, 14.1. HRMS-FAB: m/z calcd for C₁₅H₁₉N₂O₂S [M + H]: 291.1167; found: 291.1169.
2-Amino-4-hexylthiazole Mp 45-46 ˚C. IR (Nujol): 3432, 3235, 1606, 1508, 1103, 706 cm^-¹. ^¹H NMR (400 MHz, CDCl₃, TMS): δ = 6.08 (s, 1 H), 4.92 (s, 2 H), 2.52 (t, J = 6.9 Hz, 2 H), 1.56-1.68 (m, 2 H), 1.24-1.39 (m, 6 H), 0.88 (t, J = 6.9 Hz, 3 H). ^¹³C NMR (100 MHz, CDCl₃, TMS): δ = 167.0, 153.7, 102.2, 31.7, 31.6, 29.0, 28.7, 22.6, 14.1. HRMS-FAB: m/z calcd for C₉H₁₇N₂S [M + H]: 185.1112; found: 185.1106.
2-Phenyl-4-butylthiazole
Oil. IR(neat): 2956, 2929, 2859, 1516, 1498, 1460, 1436, 1244, 1004, 763, 689 cm^-¹. ^¹H NMR (400 MHz, CDCl₃, TMS): δ = 7.93 (dd, J = 1.4, 8.0 Hz, 2 H), 7.38-7.45 (m, 3 H), 6.86 (s, 1 H).
2-Methyl-4-phenylthiazole Mp 60 ˚C; lit.^4h 64 ˚C. ^¹H NMR (400 MHz, CDCl₃, TMS): δ = 7.87 (d, J = 8.3 Hz, 2 H), 7.41 (t, J = 7.5 Hz, 2 H), 7.32 (t, J = 7.5 Hz, 1 H), 7.31 (s, 1 H), 2.78 (s, 3 H).
2-(4-Methylphenyl)-4-phenylthiazole Mp 126 ˚C. IR (Nujol): 974, 815, 741, 690, 676 cm^-¹. ^¹H NMR (400 MHz, CDCl₃, TMS): δ = 8.00 (d, J = 8.2 Hz, 2 H), 7.94 (d, J = 8.2 Hz, 2 H), 7.41-7.48 (m, 3 H), 7.35 (t, J = 7.3 Hz, 1 H), 7.26 (d, J = 6.5 Hz, 2 H), 2.41 (s, 3 H). ^¹³C NMR (100 MHz, CDCl₃, TMS): δ = 168.0, 156.1, 140.3, 134.6, 131.1, 129.6, 128.7, 128.1, 126.5, 126.4, 112.1, 21.4. HRMS-FAB: m/z calcd for C₁₆H₁₄NS [M + H]: 252.0847; found: 252.0851.
2-(4-Methoxyphenyl)-4-phenylthiazole Mp 97-98 ˚C. IR (Nujol): 1256, 1173, 979, 833, 738 cm^-¹. ^¹H NMR (400 MHz, CDCl₃, TMS): δ = 7.96-8.02 (m, 4 H), 7.40-7.48 (m, 3 H), 7.34 (t, J = 7.4 Hz, 1 H), 6.98 (d, J = 8.9 Hz, 2 H), 3.88 (s, 3 H). ^¹³C NMR (100 MHz, CDCl₃, TMS): δ = 177.6, 161.4, 134.9, 133.6, 128.9, 128.3, 127.0, 126.6, 115.0, 114.5, 111.9, 55.7. HRMS-FAB: m/z calcd for C₁₆H₁₄NOS [M + H]: 268.0796; found: 268.0802.
2-(4-Nitrophenyl)-4-phenylthiazole Mp 164-165 ˚C. IR (Nujol): 1514, 1339, 849 cm^-¹. ^¹H NMR (400 MHz, CDCl₃, TMS): δ = 8.33 (d, J = 8.9 Hz, 2 H), 8.22 (d, J = 8.9 Hz, 2 H), 8.00 (d, J = 8.2 Hz, 2 H), 7.63 (s, 1 H), 7.48 (t, J = 7.4 Hz, 2 H), 7.40 (t, J = 7.4 Hz, 1 H). ^¹³C NMR (100 MHz, CDCl₃, TMS): δ = 164.8, 157.3, 148.4, 139.1, 133.9, 128.9, 128.7, 127.1, 126.5, 124.3, 114.6. HRMS-FAB: m/z calcd for C₁₅H₁₁N₂O₂S [M + H]: 283.0541; found: 283.0547.
2-Amino-4-phenylthiazole Mp 145-147 ˚C. IR (Nujol): 3433, 1595, 1518, 1038, 714 cm^-¹. ^¹H NMR (400 MHz, CDCl₃, TMS): δ = 7.78 (d, J = 8.0 Hz, 2 H), 7.38 (t, J = 7.6 Hz, 2 H), 7.29 (t, J = 7.4 Hz, 1 H), 6.73 (s, 1 H), 5.03 (s, 2 H). ^¹³C NMR (100 MHz, CDCl₃, TMS): δ = 167.0, 151.3, 134.6, 128.6, 127.7, 126.0, 102.9. HRMS-FAB: m/z calcd for C₉H₉N₂S [M + H]: 177.0486; found: 177.0485.

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