Photochemical substitution of halogenopyrrole derivatives

Abstract

The photochemical behaviour of some iodo substituted pyrroles when they are irradiated in the presence of an aromatic compound is reported. N-Methyl-3,4-diiodopyrrole-2-carbaldehyde and 5-iodopyrrole-2-carbaldehyde are unreactive when they are irradiated in benzene solution. In contrast, ethyl 3,4-dimethyl-5-iodopyrrole-2-carboxylate gives a 1∶1 mixture of ethyl 3,4-dimethyl-5-phenylpyrrole-2-carboxylate and ethyl 3,4-dimethylpyrrole-2-carboxylate in quantitative yields. The same reaction when attempted with acetonitrile as solvent gives ethyl 3,4-dimethylpyrrole-2-carboxylate as the sole product in quantitative yield. Use of 4,5-diiodopyrrole-2-carbaldehyde as substrate and irradiation in benzene gives the corresponding 5-phenyl derivative. The same behaviour is observed with m-xylene, thiophene and 2-chlorothiophene as solvents. With acetonitrile as solvent, the reaction with benzene does not work. With 2-methylthiophene as solvent 2-(5-methyl-2-thienyl)-3-iodopyrrole is obtained as the sole product. The observed behaviour can be explained on the basis of the previously reported data on the mechanism of the photochemical arylation of halogenothiophene derivatives.

References

1. R. Antonioletti, M. D'Auria, A. De Mico, G. Piancatelli and A. Scettri, Tetrahedron, 1985, 41, 3441.
2. R. Antonioletti, M. D'Auria, A. De Mico, G. Piancatelli and A. Scettri, J. Chem. Soc., Perkin Trans. 1, 1985, 1285.
3. R. Antonioletti, M. D'Auria, F. D'Onofrio, G. Piancatelli and A. Scettri, J. Chem. Soc., Perkin Trans. 1, 1986, 1755.
4. M. D'Auria, R. Antonioletti, A. De Mico and G. Piancatelli, Heterocycles, 1986, 24, 1575.
5. M. D'Auria, A. De Mico, F. D'Onofrio and G. Piancatelli, J. Chem. Soc., Perkin Trans. 1, 1987, 1777.
6. M. D'Auria, A. De Mico, F. D'Onofrio and G. Piancatelli, Gazz. Chim. Ital., 1989, 119, 381.
7. M. D'Auria, A. De Mico, F. D'Onofrio, D. Mendola and G. Piancatelli, J. Photochem. Photobiol., A: Chem., 1989, 47, 191.
8. M. D'Auria, Gazz. Chim. Ital., 1994, 124, 195.
9. M. D'Auria, J. Photochem. Photobiol., A: Chem., 1995, 91, 187.
10. F. Elisei, L. Latterini, G. G. Aloisi and M. D'Auria, J. Phys. Chem., 1995, 99, 5365.
11. M. Farnier and P. Fournari, Bull. Soc. Chim. Fr., 1973, 351.
12. A. McKillop, J. S. Fowler, M. J. Zelesko, J. D. Hunt, E. C. Taylor and G. McGillivray, Tetrahedron Lett., 1969, 2423.
13. R. A. Hollins, L. A. Colnago, V. M. Salim and M. C. Seidl, J. Heterocycl. Chem., 1979, 16, 993.
14. K. Ichimura, S. Ichikawa and K. Imamura, Bull. Chem. Soc. Jpn, 1976, 49, 1157.
15. M. Scarsella and G. Sleiter, Gazz. Chim. Ital., 1988, 118, 757.
16. D. Jerchel and H. E. Herck, Justus Liebigs Ann. Chem., 1938, 177.
17. E. B. Merkushev, N. D. Simakhina and G. M. Koveshnikova, Synthesis, 1980, 4.
18. M. D'Auria and G. Mauriello, Tetrahedron Lett., 1995, 36, 4883.
19. H. Berner, G. Schulz and H. Reinshagen, Monatsh. Chem., 1977, 108, 285.
20. H. Berner, G. Schulz, G. Fischer and H. Reinshagen, Monatsh. Chem., 1978, 109, 557.
21. K. Maruyama, T. Otsuki and H. Tamiaki, Bull. Chem. Soc. Jpn, 1985, 58, 3043.
22. J. Meng, M. Shen, D. Fu, Z. Gao, R. Wang, H. Wang and T. Matsuura, Synthesis, 1990, 719.
23. N. A. Gordeeva, M. A. Kirpichenok and I. I. Grandberg, Khim. Geterotsilk. Soedin., 1990, 1469.
24. K. Seki, K. Ohkura, M. Terashima and Y. Kanaoka, Heterocycles, 1984, 22, 2347.
25. H.-S. Ring and H. Sakurai, J. Chem. Soc., Chem. Commun., 1972, 594.
26. K. Seki, K. Ohkura, M. Terashima and Y. Kanaoka, Heterocycles, 1986, 24, 799.
27. K. Ohkura, K. Seki, M. Terashima and Y. Kanaoka, Heterocycles, 1990, 30, 957.
28. D. W. Allen, D. J. Buckland, B. G. Hutley, A. C. Oades and J. B. Turner, J. Chem. Soc., Perkin Trans. 1, 1977, 621.
29. H. Ikehira, T. Matsuura and I. Saito, Tetrahedron Lett., 1985, 26, 1743.
30. V. Nair, S. G. Richardson and R. E. Coffman, J. Org. Chem., 1982, 47, 4520.
31. V. Nair, D. A. Young and R. Desilvia, J. Org. Chem., 1987, 52, 1344.
32. C. F. Candy, R. A. Jones and P. H. Wright, J. Chem. Soc. C., 1970, 2563.
33. J.-P. Boukou-Poba, M. Farnier and R. Guilard, Can. J. Chem., 1981, 59, 2962.
34. J. Wang and A. I. Scott, Tetrahedron Lett., 1996, 37, 3247.
35. D'Auria, unpublished work.
36. H. Fischer and H. Hofelmann, Justus Liebigs Ann. Chem., 1938, 553, 216.