We are grateful to Dr. P. Kunzelmann, Dr. H. Hiller, and Frau G. Rissmann for some spectroscopic measurements as well as to J. Schwab for preparative work. We appreciate financial support from the Deutsche Forschungsgemeinschaft, Fonds der Chemischen Industrie, and BASF Aktiengesellschaft, Ludwigshafen.
Dedicated to Professor Hermann Schildknecht on the occasion of his 60th birthday
The complete manuscript of this communication appears in: Angew. Chem. Suppl. 1982, 1491. DOI:10.1002/anie.198214910