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Synlett 2008(5): 725-727  
DOI: 10.1055/s-2008-1032100
LETTER
© Georg Thieme Verlag Stuttgart · New York

Ytterbium(III) Triflate Catalyzed One-Pot Synthesis of 1,3-Thiazolidin-2-imines­ from Epichlorohydrin and Thioureas

Weike Su*, Chuangwei Liu, Weiguang Shan
College of Pharmaceutical Sciences, Zhejiang University of Technology, Zhejiang Key Laboratory of Pharmaceutical Engineering, Hangzhou­ 310014, P. R. of China
Fax: +86(571)88320752; e-Mail: suweike@zjut.edu.cn;
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Received 21 November 2007
Publikationsdatum:
26. Februar 2008 (online)

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Abstract

2-Arylimino-3-aryl-1,3-thiazolidines were successfully obtained from epichlorohydrin and thioureas in DMF catalyzed by Yb(OTf)3. Inversion of the configuration occurred at the chiral center of the epoxide.

Key words

ytterbium triflate - cyclization - thiazolidinimine - epi­chlorohydrin - thiourea

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HPLC conditions: DAICEL CHIRALCELOD-H-4.6 × 250 mm, hexane-i-PrOH-Et2NH = 90:10:1 (% v/v/v), 236 nm, 0.8 mL/min, 30 °C.

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Typical Experimental Procedure for Cyclization of Thioureas with Epoxides
Thiourea 2 (5 mmol) was added to a stirred mixture of DMF (20 mL) and epoxide 1. The reaction was monitored by TLC until completion. The temperature of this reaction was kept at 70 °C (or r.t.) for 72 h, then the solvent was removed by distillation at reduced pressure. The residual was purified on silica gel (PE-EtOAc-CH2Cl2 = 10:1:1) to give thiazolindinimes 3 as white crystals.
Spectral data for obtained compounds:
(3-Phenyl-2-(phenylimino)thiazolidin-5-yl)methanol (3a)
White crystalline solid; mp 86.0-88.0 °C. ESI-MS: m/z (%) = 282.9 (70), 163.8 (100), 117.9 (56). Anal. Calcd for C16H16N2OS: C, 67.58; H, 5.67; N, 9.85; Found: C, 67.50; H, 5.78; N, 9.79. IR (KBr): νmax = 3274, 1645, 1595, 1529 cm-1. 1H NMR (400 MHz, CDCl3,): δ = 2.13 (dd, 1 H, J 1 = 5.6 Hz, J 2 = 1.2 Hz), 2.46 (d, 1 H, J = 6.4 Hz,), 3.20 (m, 1 H), 3.84 (q, 1 H, J = 7.2 Hz), 3.98 (q, 1 H, J = 5.6 Hz), 6.16 (s, 1 H), 6.98-7.53 (m, 10 H). 13C NMR (100 MHz, CDCl3): δ = 24.5, 32.0, 55.2, 119.3 (2 × CH), 123.0, 128.5, 128.7 (2 × CH), 130.4 (4 × CH), 138.4, 141.0, 153.9.
(3-Butyl-2-(phenylimino) thiazolidin-5-yl)methanol (3h)
White crystalline solid; mp: 69.4-71.5 °C. MS (EI): m/z (%) = 265 (4) [M+ + 1], 231 (85), 132 (65), 106 (100). Anal. Calcd for C14H20N2OS: C, 63.60; H, 7.62; N, 10.60. Found: C, 63.51; H, 7.81; N, 10.52. IR (KBr): νmax = 3355, 2949, 1639, 1510 cm-1. 1H NMR (400 MHz, CDCl3): δ = 0.87 (t, 3 H, J = 7.2 Hz), 1.24 (m, 2 H), 1.40 (m, 2 H,), 2.07 (d, 1 H, J = 5.2 Hz), 2.41 (d, 1 H, J = 5.6 Hz), 3.16 (m, 3 H), 3.68 (m, 1 H), 3.98 (q, 1 H, J = 5.2 Hz), 4.25 (s, 1 H), 7.26-7.47 (m, 5 H). 13C NMR (100 MHz, CDCl3): δ = 13.5, 19.7, 24.4, 32.0, 32.1, 40.2, 54.9, 127.7 (2 × CH), 128.5, 129.9 (2 × CH), 141.5, 156.6.