Photocycloaddition of N-alkoxycarbonylbenzoxazole-2-thiones to alkenes: isolation of stable aminothietanes

Abstract

N-Alkoxy- and N-aryloxycarbonylbenzoxazole-2-thiones 1 undergo photocycloaddition with alkenes 2 in a regiospecific manner to yield stable spirocyclic aminothietanes 3–4, 7–9 and 11 in fair to high yields.

References

1. (a) M. Sakamoto, T. Fujita, S. Watanabe and T. Nishio, Yuki Gousei Kagaku Kyokaishi, 1995, 52, 658; (b) T. Nishio and M. Sakamoto, in Reviews on Hetreoatom Chemistry, ed. S. Oae, MYU, Tokyo, 1995, vol. 12, p. 23 and references cited therein; (c) M. Sakamoto and T. Nishio, in Reviews on Heteroatom Chemistry, ed. S. Oae, MYU, Tokyo, vol. 12, p. 53 and references cited therein; (d) T. Nishio, Y. Mori, I. Iida and A. Hosomi, Helv. Chim. Acta, 1994, 77, 981; (e) T. Nishio, Y. Mori, I. Iida and A. Hosomi, J. Chem. Soc., Perkin Trans. 1, 1996, 921; (f) T. Nishio, J. Chem. Soc., Perkin Trans. 1, 1998, 1007.
2. J. D. Coyle, Tetrahedron, 1985, 41, 539; M. Machida, K. Oda, E. Sato and Y. Kanaoka, Yuki Gosei Kagaku Kyokaisi, 1986, 44, 1071; J. D. Coyle and P. A. Rapley, J. Chem. Soc., Perkin Trans. 1, 1986, 2273.
3. Aminothietanes have not been isolated except for one example by us. By the photochemical cycloaddition of 1,3,3-trimethylindole-2-thione and 2-methylpropene, 1,3,3,′3′-pentamethy1-2,3-dihydrospiro[in dole-2,2′-thietane] was isolated, though in only 8% yield; T. Nishio, N. Okuda and Y. Omote, J. Chem. Soc., Perkin Trans. 1, 1988, 1663.
4. For example, spirocyclic aminothietane 3: IR (KBr) 1725 and 1620 cm ^–1; δ_H 1.10 (3H, s), 1.39 (3H, s), 1.55 (3H, s), 1.71 (3H, s), 3.91 (3H, s), 6.80–6.96 (3H, m) and 7.37–7.43 (1H, m); δ_c 21.5 (q), 22.1 (q), 26.3 (q), 29.8 (q), 48.0 (s), 52.9 (q), 62.9 (s), 108.2 (d), 109.8 (s), 115.4 (d), 121.1 (d), 123.9 (d), 129.8 (s), 148.2 (s) and 152.5 (s). The structure of the sultine 13 was finally confirmed by X-ray structural analysis. Details will be reported elsewhere.