1. Murata, S.; Sugimoto, T.; Matsuura, S. Heterocycles 1987, 26, 883.
2. Woydowski, K.; Liebscher, J. Synthesis, in press.
3. El Meslouhi, H.; Essassi, E. M.; Zerzouf, A.; Salem, M.; Petrus, C.; Viallefont, P. Bull. Soc. Chim. Belg. 1996, 105, 785.
4. Mori. K.; Iwasawa, H. Tetrahedron 1980, 36, 87.
5. Full details have been deposited at the Fachinformationszentrum Karlsruhe, 76344 Eggenstein-Leopoldshaven, Germany; this material can be obtained on quoting a full literature citation and deposition number CSD-408180.