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Synlett 2007(4): 0646-0648  
DOI: 10.1055/s-2007-967975
LETTER
© Georg Thieme Verlag Stuttgart · New York

Ytterbium(III) Triflate Catalyzed [3+2] Cycloaddition of N-Arylimines and Epoxides: A Novel and Solvent-Free Synthesis of Substituted 1,3-Oxazolidines

Chuanming Yu, Xiaoping Dai, Weike Su*
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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Publication History

Received 23 November 2006
Publication Date:
21 February 2007 (online)

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Abstract

The [3+2] cycloaddition of N-arylimines and epoxides was efficiently catalyzed by ytterbium(III) triflate under solvent-free conditions to afford 1,3-oxazolidines in high yields.

Key words

ytterbium(III) triflate - cycloaddition - 1,3-oxazolidines - N-arylimines - epoxides

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5-Chloromethyl-2,3-diphenyloxazolidine ( 3a): MS (EI): m/z (%) = 273 (100), 196 (84), 132 (67); IR (film): 1297, 1207, 1109 cm- 1; 1H NMR (400 MHz, CDCl3):
δ (cis-3a) = 7.48-7.36 (m, 5 H), 7.16 (t, J = 7.6 Hz, 2 H), 6.75 (t, J = 7.6 Hz, 1 H), 6.52 (d, J = 7.6 Hz, 2 H), 5.87 (s, 1 H), 4.59-4.50 (m, 1 H), 3.96 (dd, J = 6.0, 8.4 Hz, 1 H), 3.85-3.59 (m, 2 H), 3.51 (dd, J = 8.4, 8.4 Hz, 1 H); 13C NMR (100 MHz, CDCl3-TMS): δ (cis-3a) = 145.4, 139.3, 129.1, 128.9, 128.8, 127.1, 118.2, 113.9, 92.9, 76.7, 52.2, 44.6; 1H NMR (400 MHz, CDCl3): δ (trans-3a) = 7.48-7.36 (m, 5 H), 7.16 (t, J = 7.6 Hz, 2 H), 6.75 (t, J = 7.6 Hz, 1 H), 6.52 (d, J = 7.6 Hz, 2 H), 6.01 (s, 1 H), 4.59-4.50 (m, 1 H), 3.98 (dd, J = 6.0, 8.4 Hz, 1 H), 3.85-3.59 (m, 2 H), 3.51 (dd, J = 8.4, 8.4 Hz, 1 H); 13C NMR (100 MHz, CDCl3-TMS): δ (trans-3a) = 145.2, 139.5, 129.1, 129.0, 128.7, 126.8, 117.9, 113.0, 92.4, 75.2, 51.2, 44.2; Anal. Calcd for C16H16ClNO: C, 70.20; H, 5.89; N, 5.12. Found: C, 70.22; H, 5.90; N, 5.10.
5-Chloromethyl-2,2-diphenyl-3- p -tolyloxazolidine ( 3i): yellow crystals; mp 125-128 °C; MS (EI): m/z (%) = 363 (22), 286 (64), 146 (100); IR (film): 1322, 1200, 1106 cm- 1; 1H NMR (400 MHz, CDCl3): δ = 7.50-7.24 (m, 10 H), 6.81 (d, J = 8.0 Hz, 2 H), 6.37 (d, J = 8.0 Hz, 2 H), 4.40-4.34 (m, 1 H), 3.84-3.67 (m, 4 H), 2.15 (s, 3 H); 13C NMR (100 MHz, CDCl3-TMS): δ = 142.4, 141.2, 140.5, 129.2, 129.0, 128.8, 128.5, 128.3, 127.9, 126.8, 114.8, 99.7, 74.1, 52.0, 44.7, 20.2; Anal. Calcd for C23H22ClNO: C, 75.92; H, 6.09; N, 3.85. Found: C, 75.90; H, 6.10; N, 3.84.

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A mixture of epoxide 1a (0.28 g, 3 mmol), N-arylimine 2a (0.36 g, 2 mmol), and Yb(OTf)3 (0.06 g, 5 mol%) was stirred at 40 °C for 8 h. After complete conversion into 3a, as indicated by TLC, the reaction mixture was purified by silica gel column chromatography using PE-EtOAc (10:1) as eluent to afford the pure product 5-chloromethyl-2,3-diphenyloxazolidine (3a, 0.46 g, 85%, Table [2] ).

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HPLC conditions: Chiracel OD 4.6 × 250mm, hexane-
i-PrOH (85:15), 25 °C.