1. I. A. Abronin, A. V. Cherkasov, and G. M. Zhidomirov, Zh. Fiz. Khim.,54, 1888 (1980).
2. I. A. Abronin, N. D. Chuvylkin, and G. M. Zhidomirov, Izv. Sib. Otd. Akad. Nauk SSSR, Ser. Khim. Nauk,3, No. 7, 96 (1980).
3. T. Sordo, J. Bertran, and E. Canadell, J. Chem. Soc. Perkin Trans. 2, No. 11, 1486 (1979).
4. H.-J. Köhler and H. Lischka, J. Am. Chem. Soc.,101, 3479 (1979).
5. J. C. Rayez and J. J. Dannenberg, Tetrahedron Lett., No. 8, 671 (1977).