Photochemistry of some trialkylsilyloxybenzylidenemalonic acid derivatives. C–Si bond fragmentation in a polarized excited state

Abstract

Photolysis of 3-(tert-butyldimethylsilyloxyphenyl)methylenemalonodinitrile (2) in a polar medium leads to C–Si cleavage via the polarized singlet excited state. The thus formed tert-butyl radicals diffuse out of cage and are trapped by further molecules of 2. In contrast, the photochemical alkylation of benzylidenemalonodinitrile by tert-butyldimethylsilyl phenyl ether occurs via the radical cation and requires phenanthrene sensitization. In an apolar solvent, 2 undergoes only a slow dimerization and gives two (one main) cyclobutanes. Photoinduced cleavage is not observed neither with the corresponding diester nor with the 2-silyloxy analogue of 2 (the lowest excited singlet of the latter compound is an ICT state).

References

1. F. D. Saeva, Top. Curr. Chem., 1991, 156, 59.
2. A. Albini, M. Mella and M. Freccero, Tetrahedron, 1994, 50, 575.
3. R. Popielartz and D. R. Arnold, J. Am. Chem. Soc., 1990, 112, 3068.
4. P. Maslak, W. H. Chapman, T. M. Vallombroso and B. A. Watson, J. Am. Chem. Soc., 1995, 117, 12 380.
5. Photoinduced Electron Transfer, ed. M. A. Fox and M. Chanon, Elsevier, Amsterdam, 1988.
6. Top. Curr. Chem., ed. J. Mattay, 1990, 156; 1990, 158; 1991, 159; 1992, 163; 1993, 168.
7. Advances in Electron Transfer Chemistry, ed. P. S. Mariano, JAI Press, Greenwich, CT, 1991–94, vol. 1–4.
8. F. D. Lewis, Acc. Chem. Res., 1986, 19, 401.
9. E. R. Gaillard and D. G. Whitten, Acc. Chem. Res., 1996, 29, 292.
10. I. R. Gould, R. H. Young, L. J. Mueller and S. Farid, J. Am. Chem. Soc., 1994, 116, 8176; I. R. Gould, R. H. Young, L. J. Mueller, A. C. Albrecht and S. Farid, J. Am. Chem. Soc., 1994, 116, 8188.
11. M. Fagnoni, M. Mella and A. Albini, J. Am. Chem. Soc., 1995, 117, 7877; M. Fagnoni, M. Mella and A. Albini, Tetrahedron, 1995, 51, 859.
12. J. W. Verhoeven, T. Scherer, B. Wegewijs, R. M. Hermant, J. Jortner, M. Bixon, S. Depaemelaere and F. C. De Schryver, Recl. Trav. Chim. Pays-Bas, 1995, 114, 443; P. Pasman, J. M. Verhoeven and T. J. de Boer, Tetrahedron, 1976, 32, 2827.
13. M. N. Paddon Row, Acc. Chem. Res., 1994, 27, 18.
14. F. D. Lewis, G. D. Reddy, D. M. Bassani, S. Schneider and M. Gahr, J. Am. Chem. Soc., 1994, 116, 597; F. D. Lewis, D. M. Bassani, E. L. Burch, B. E. Cohen, J. A. Engleman, G. D. Reddy, S. Schneider, P. Jaeger, P. Gedeck and M. Gahr, J. Am. Chem. Soc., 1995, 117, 660.
15. A. Albini and S. Spreti, Tetrahedron, 1984, 40, 2975.
16. T. van der Haar, A. Hebecker, Y. Il'ichev, Y. B. Jiang, W. Kuehnle and K. A. Zachariasse, Recl. Trav. Chim. Pays-Bas, 1995, 114, 430.
17. Z. Grabowski and J. Dobkovski, Pure Appl. Chem., 1983, 55, 245.
18. M. Mella, N. d'Alessandro, M. Freccero and A. Albini, J. Chem. Soc., Perkin Trans. 2, 1993, 515.
19. K. Mizuno and Y. Otsuji, Top. Curr. Chem., 1994, 169, 301; K. Mizuno, M. Ikeda and Y. Otsuji, Chem. Lett., 1988, 1507; K. Mizuno, K. Nakanishi, A. Tachibane and Y. Otsuji, J. Chem. Soc., Chem. Commun., 1991, 344.
20. S. Kyushin, K. Masuda, K. Matsushita, Y. Nadaira and M. Ohashi, Tetrahedron Lett., 1990, 31, 6395.
21. R. M. Dodson and A. G. Zielske, J. Org. Chem., 1967, 32, 28; D. N. Harp and C. Heitner, J. Org. Chem., 1970, 35, 3256; O. L. Chapman and W. R. Adams, J. Am. Chem. Soc., 1968, 90, 2333.
22. D. Haag and H. D. Sharf, J. Org. Chem., 1996, 61, 6127.
23. F. D. Lewis, Adv. Photochem., 1986, 13, 165.
24. G. Kaupp, Methoden der Organischen Chemie, Thieme, Stuttgart, 1975, vol. IV/5a, p. 248.
25. T. Kitamura, S. Toki and S. Sakurai, Kokaganu Toronkai Koen Yoshishu, 1979, 190, through Chem. Abstr., 1980, 93, 70 806.
26. G. G. Hess, F. W. Lampe and L. H. Sommer, J. Am. Chem. Soc., 1965, 87, 5327.
27. H. G. Sturz and C. R. Noller, J. Am. Chem. Soc., 1949, 71, 2949.
28. W. Baker and C. S. Howes, J. Chem. Soc., 1953, 122.
29. J. M. Bruce, D. Creed and K. Dawes, J. Chem. Soc. (C), 1971, 3749.
30. S. K. Chaudhary and O. Hernandez, Tetrahedron Lett., 1979, 99.
31. E. Campaigne and W. L. Roelofs, J. Org. Chem., 1965, 30, 396.