1. The results are part of the Dissertation by Universität Würzburg, 1991.
2. , Tetrahedron Lett. 1968, 4885–4887.
3. One of us (H. Q.) apologizes to the discoverers for having erroneously credited[4] G. Vossen[5] with the first reaction of this type.
4. Dissertation, Universität Bonn, 1910.