o-Aminothiophenol in Reactions with Carbonyl Compounds and Isocyanides: A Word of Caution

Abstract

The reaction of o-aminothiophenol with carbonyl compounds and t-BuNC was revisited and shown to provide 1-[1,3-benzothiazol-3(2H)-yl]methanimines (not described hitherto) and not the earlier reported 4H-benzo[1,4]thiazine. To isolate the latter using this reaction a due amount of caution and structure scrutiny is warranted. The basis for assignment of the products to both structural classes is provided.

Key words

isocyanide-based multicomponent reactions - bifunctional reagents - isocyanide-intercepting nuceophiles - thiophenol - amidines

References and Notes

• 1 Krasavin M. Parchinsky V. Synlett  2008,  645 
• 2 Kysil V. Khvat A. Tsirulnikov S. Tkachenko S. Williams C. Churakova M. Ivachtchenko A. Eur. J. Org. Chem.  2010,  1525 
• 3 Shaabani A. Maleki A. Moghimi-Rad J. J. Org. Chem.  2007,  72:  6309 
• 4 Heravi MM. Baghernejad B. Oskooie HA. Tetrahedron Lett.  2009,  50:  767 
• 5 Ugi I. Steinbrückner C. Chem. Ber.  1961,  94:  734 
• 6 Heravi MM. Baghernejad B. Oskooie HA. Synlett  2009,  1123 
• 9a Saegusa T. Ito Y. Kobayashi S. Hirota K. Yoshioka H. Tetrahedron Lett.  1966,  7:  6121 
• 9b Smith R. Livinghouse T. Synth. Commun.  1984,  14:  639 
• 9c Hashida Y. Imai A. Sekiguchi S. J. Heterocycl. Chem.  1989,  26:  9901 
• 9d Simon JR. Synthesis  2001,  2011 
• 9e Cao C. Shi Y. Odom AL. J. Am. Chem. Soc.  2003,  125:  2880 

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Characterization Data for Selected Compounds
Compound 5a: emerald green solid, mp 172 ˚C (decomp.). ^¹H NMR (500 MHz, DMSO-d ₆): δ = 6.95-7.07 (m, 3 H), 6.71 (td, J = 7.6, 1.3 Hz, 1 H), 5.78 (s, 1 H), 1.63-1.78 (m, 2 H), 1.42-1.56 (m, 7 H), 1.33 (s, 9 H), 1.12-1.27 (m, 1 H). ^¹³C NMR (125 MHz, DMSO-d ₆): δ = 156.2, 140.9, 126.2, 125.0, 118.9, 118.8, 117.2, 57.3, 55.3, 33.0, 28.6, 25.4, 21.0. LC-MS: m/z = 289 [M + H]. Anal. Calcd for C₁₇H₂₄N₂S: C, 70.79; H, 8.39; N, 9.71. Found: C, 70.72; H, 8.48; N, 9.83.
Compound 5b: brown solid, mp 169-172 ˚C(br). ^¹H NMR (500 MHz, DMSO-d ₆): δ = 7.05 (d, J = 7.6 Hz, 1 H), 6.97 (t, J = 7.6 Hz, 1 H), 6.87 (d, J = 7.6 Hz, 1 H), 6.70 (t, J = 7.6 Hz, 1 H), 6.05 (s, 1 H), 2.01-2.14 (m, 2 H), 1.43-1.73 (m, 6 H), 1.33 (s, 9 H). ^¹³C NMR (125 MHz, DMSO-d ₆): δ = 156.0, 142.7, 126.3, 125.3, 118.8, 116.8, 67.7, 55.0, 36.4, 28.7, 23.6. LC-MS: m/z = 275 [M + H]. Anal. Calcd for C₁₆H₂₂N₂S: C, 70.03; H, 8.08; N, 10.21. Found: C, 69.89; H, 8.01; N, 10.13.
Compound 5e: brown solid, mp 186 ˚C (decomp.). Single diastereomer! ^¹H NMR (500 MHz, DMSO-d ₆): δ = 6.98 (d, J = 7.6 Hz, 1 H), 6.93 (t, J = 7.6 Hz, 1 H), 6.82 (d, J = 7.6 Hz, 1 H), 6.67 (t, J = 7.6 Hz, 1 H), 5.77 (s, 1 H), 2.07 (d, J = 12.6 Hz, 2 H), 1.54 (m, 4 H), 1.35 (s, 9 H), 1.15-1.25 (m, 2 H), 1.00 (m, 1 H), 0.82 (s, 9 H). ^¹³C NMR (125 MHz, DMSO-d ₆): δ = 152.6, 141.5, 126.0, 124.6, 118.3, 117.6, 116.5, 56.5, 55.5, 46.9, 35.5, 32.1, 28.7, 27.3, 23.1. LC-MS: m/z = 345 [M + H]. Anal. Calcd for C₂₁H₃₂N₂S: C, 73.20; H, 9.36; N, 8.13. Found: C, 73.29; H, 9.49; N, 8.23.
Compound 4b: brown oil. ^¹H NMR (500 MHz, DMSO-d ₆): δ = 7.98 (s, 1 H), 7.48 (d, J = 7.8 Hz, 1 H), 7.10 (d, J = 7.8 Hz, 1 H), 6.98 (t, J = 7.8 Hz, 1 H), 6.82 (t, J = 7.8 Hz, 1 H), 2.76-2.92 (m, 2 H), 1.76-2.02 (m, 4 H), 1.58-1.74 (m, 2 H), 1.20 (s, 9 H). ^¹³C NMR (125 MHz, DMSO-d ₆): δ = 141.8, 141.4, 125.2, 125.0, 121.7, 121.4, 111.4, 85.2, 54.6, 30.6, 23.6. LC-MS: m/z = 275 [M + H]. Anal. Calcd for C₁₆H₂₂N₂S: C, 70.03; H, 8.08; N, 10.21. Found: C, 70.12; H, 8.13; N, 10.30.
Compound 4c: dark yellow solid, mp 182-184 ˚C. ^¹H NMR (500 MHz, DMSO-d ₆): δ = 8.01 (s, 1 H), 7.59 (d, J = 7.8 Hz, 1 H), 7.15 (dd, J = 7.8, 1.3 Hz, 1 H), 6.99 (td, J = 7.8, 1.3 Hz, 1 H), 6.84 (td, J = 7.8, 1.3 Hz, 1 H), 3.95 (dd, J = 12.6, 4.6 Hz, 2 H), 3.45 (t, J = 12.6 Hz, 2 H), 3.05 (td, J = 12.6, 4.6 Hz, 2 H), 1.88 (d, J = 12.6 Hz, 2 H), 1.20 (s, 9 H). ^¹³C NMR (125 MHz, DMSO-d ₆): δ = 142.4, 141.7, 125.2, 124.4, 121.8, 121.6, 112.7, 80.2, 65.3, 54.7, 37.5, 30.5. LC-MS: m/z = 291 [M + H]. Anal. Calcd for C₁₆H₂₂N₂OS: C, 66.17; H, 7.64; N, 9.65. Found: C, 66.22; H, 7.70; N, 9.71. Compound 4e: pale yellow solid, mp 181-183 ˚C. Single diastereomer! ^¹H NMR (500 MHz, DMSO-d ₆): δ = 7.98 (s, 1 H), 7.88 (d, J = 7.8 Hz, 1 H), 7.11 (dd, J = 7.8, 1.3 Hz, 1 H), 6.96 (td, J = 7.8, 1.3 Hz, 1 H), 6.81 (td, J = 7.8, 1.3 Hz, 1 H), 2.52-2.60 (m, 2 H), 2.03 (d, J = 12.6 Hz, 2 H), 1.81 (d, J = 12.6 Hz, 2 H), 1.17-1.30 (m, 11 H), 0.87 (s, 9 H). ^¹³C NMR (125 MHz, DMSO-d ₆): δ = 143.0, 141.7, 124.8, 121.6, 121.2, 113.8, 82.7, 54.6, 45.4, 37.5, 32.0, 30.6, 27.4, 24.8. LC-MS: m/z = 345 [M + H]. Anal. Calcd for C₂₁H₃₂N₂S: C, 73.20; H, 9.36; N, 8.13. Found: C, 73.17; H, 9.34; N, 8.02. Compound 4f: beige solid, mp 201 ˚C (decomp.). ^¹H NMR (500 MHz, DMSO-d ₆): δ = 8.07 (s, 1 H), 7.42 (d, J = 7.8 Hz, 1 H), 7.23 (d, J = 8.6 Hz, 2 H), 7.20 (d, J = 7.8 Hz, 1 H), 7.07 (t, J = 7.8 Hz, 1 H), 6.93 (s, 1 H), 6.90 (t, J = 7.8 Hz, 1 H), 6.83 (d, J = 8.6 Hz, 2 H), 3.70 (s, 3 H), 1.12 (s, 9 H). ^¹³C NMR (125 MHz, DMSO-d ₆): δ = 158.8, 143.6, 140.4, 134.6, 127.4, 127.0, 125.6, 122.8, 122.4, 113.6, 111.2, 65.8, 55.2, 54.1, 30.6. LC-MS: m/z = 327 [M + H]. Anal. Calcd for C₁₉H₂₂N₂OS: C, 69.90; H, 6.79; N, 8.58. Found: C, 70.03; H, 6.87; N, 8.65.

8

Crystallographic data (excluding structure factors) for the structures 4f and 5a have been deposited with the Cambridge Crystallographic Data Centre as supplementary publication numbers CCDC 774773 and CCDC 774774. Copies of the data can be obtained free of charge, on application to CCDC, 12 Union Road, Cambridge CB2 1EZ, UK [fax: [phone] or e-mail: [e-mail]].