1. a;Ficini;Tetrahedron letters,1970
2. Journ chimie ibid;Ficini;Tetrahedron letters,1980
3. a ibid;Ficini;Tetrahedron Letters Review Tetrahedron Bull SOC Chim Fr,1972
4. We all thank the Ministry of the and RhBne for financial support;Poulenc;Education science
5. For reviews see for instance a;Jones;ortschr Chem Org Nat Russ Chem Rev,1980