1. V. V. Zalesov, N. A. Pulina, and Yu. S. Andreichuk, Zh. Org. Chim., 25, 1054 (1989).
2. V. P. Kruglenko, V. P. Gnidets, N. A. Klyuev, and M. V. Povstyanoi, Khim. Geterotsikl. Soed. 533 (1987). [Chem. Heterocycl. Comp., 23, 444 (1987)].
3. H. J. Bestmann and H. Fritzsche, Chem. Ber., 94, 2477 (1961).
4. A. Schonberg and K. Sunahans, Chem. Ber., 97, 2539 (1964).
5. F. R. Hewgill, D. L. Hewitt, L. B. Howie, and W. L. Spencer, Austral. J. Chem., 30, 1971 (1977).