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Synlett 2005(1): 161-163  
DOI: 10.1055/s-2004-836032
LETTER
© Georg Thieme Verlag Stuttgart · New York

Cation Radical [3+2] Cycloaddition of Chalcone Epoxides (II): A Facile Synthesis of Highly Substituted 1,3-Oxazolidines

Congde Huo, Rui Wei, Wei Zhang, Li Yang, Zhong-Li Liu*
National Laboratory of Applied Organic Chemistry, Lanzhou University, Lanzhou, Gansu 730000, P. R. China
Fax: +86(931)8625657; e-Mail: liuzl@lzu.edu.cn;
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Publication History

Received 24 September 2004
Publication Date:
29 November 2004 (online)

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Abstract

Cycloaddition of electron-rich chalcone epoxides with N-arylimines was efficiently catalyzed by tris(4-bromophenyl)aminium hexachloroantimonate producing poly-substituted 1,3-oxazolidine derivatives in good yield.

Key words

cation radical - cycloaddition - epoxides - N-arylimines - 1,3-oxazolidines

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Representative spectral data of the products:
(±) 2,4,5-Trans,cis-2,3-diphenyl-4-(4-methoxyphenyl)-5-benzoyl-1,3-oxazolidine (trans,cis-3a): colorless prisms, mp 186-188 °C. HRMS (ESI): m/z calcd for C29H25NO3 + H+: 436.1907. Found: 436.1905. 1H NMR (300 MHz, CDCl3): δ = 3.67 (s, 3 H, OMe), 5.52 (d, J = 5.7 Hz, 1 H, H-4), 5.82 (d, J = 5.7 Hz, 1 H, H-5), 6.33 (d, J = 7.5 Hz, 2 H, N-Ph), 6.59 (d, J = 8.1 Hz, 2 H, Ar), 6.61 (t, J = 8.1 Hz, 1 H, N-Ph), 6.69 (s, 1 H, H-2), 6.85 (d, J = 8.1 Hz, 2 H, Ar), 7.01 (t, J = 7.5 Hz, 2 H, N-Ph), 7.38-7.46 (m, 5 H, Ph, Bz), 7.53-7.58 (m, 3 H, Ph, Bz), 7.70 (d, J = 7.5 Hz, 2 H, Bz). 13C NMR (75 MHz, CDCl3): δ = 55.0 (OMe), 64.1 (C-4), 81.6 (C-5), 91.3 (C-2), 113.6 (N-Ph), 113.8 (Ar), 117.2 (N-Ph), 127.2 (Ph), 128.1 (Ar), 128.5 (Bz), 128.7 (Bz), 128.8 (Ph), 128.9 (Ar, N-Ph), 128.9 (Ph), 129.1 (Ph), 133.4 (Bz), 136.0 (Ph), 138.3 (Bz), 142.2 (N-Ph), 159.1 (Ar), 193.2 (C=O).
(±)-2,4,5-Cis,trans-2,3-diphenyl-4-(4-methoxyphenyl)-5-benzoyl-1,3-oxazolidine (cis,trans-3a): colorless oil. HRMS (ESI): m/z calcd for C29H25NO3 + H+: 436.1907. Found: 436.1912. 1H NMR (300 MHz, CDCl3): d = 3.81 (s, 3 H, OMe), 5.19 (d, J = 5.1 Hz, 1 H, H-4), 5.31 (d, J = 5.1 Hz, 1 H, H-5), 6.25 (s, 1 H, H-2), 6.56 (d, J = 7.8 Hz, 2 H, N-Ph), 6.76 (t, J = 7.5 Hz, 1 H, N-Ph), 6.90 (d, J = 6.9 Hz, 2 H, Ar), 7.10 (t, J = 7.8 Hz, 2 H, N-Ph), 7.45-7.57 (m, 8 H, Ph, Bz), 7.72 (d, J = 6.9 Hz, 2 H, Ar), 7.90 (d, J = 6.9 Hz, 2 H, Bz). 13C NMR (75 MHz, CDCl3): δ = 55.2 (OMe), 61.1 (C-4), 85.2 (C-5), 92.0 (C-2), 113.1 (N-Ph), 114.5 (Ar), 116.5 (N-Ph), 127.0 (Ph), 128.0 (N-Ph), 128.9 (Ar), 129.0 (Bz), 129.1 (Ph), 129.2 (Bz), 129.3 (Ph), 130.0 (Ar), 134.2 (Bz), 137.3 (Ph), 137.7 (Bz), 140.0 (N-Ph), 159.3 (Ar), 191.7 (C=O).

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Crystal data: C29H25NO3, M = 435.50, monoclinic, a = 19.723 (4), b = 5.928 (1), c = 21.565 (4) Å, U = 2280.4 (7) Å3, T = 293 K, space group P21/c, Z = 4, µ (Mo-Kα) = 0.082 mm-1, 2973 reflections measured, 1538 unique (R int = 0.0870) which were used in all calculations. The final wR (F2) was 0.0854 (all data).