1. See reference (1).
2. W. J.Gensler, “Heterocyclic Compounds”, Vol. 4. R. C.Elderfield, Ed., John Wiley and Sons, Inc., New York, N. Y., 1952, p. 409.
3. J. M. McCall and R. E. TenBrink, Synthesis, 335 (1975).
4. F. S. Babitsev and V. A. Kovtunenko, Khim. Geterosikl. Soedin., 147 (1977).
5. Heterocyclic Systems with Bridgehead Nitrogen Atoms;Mosby,1961