Tri‐, Tetramethylbullvalene und Hexamethylbibullvalenyl

Tri‐, Tetramethylbullvalenes and Hexamethylbibullvalenyl The known monomethylbullvalenes 6 and dimethylbullvalenes 7 are supplemented by tri‐ 8 and tetramethylbullvalenes 9 as well as the hexamethylbibullvalenyl 10 . The isomer distributions of the methylbullvalenes 6–9 are determined by NMR‐spectroscopy. A vicinal arrangement of two methyl groups is not found. The 4‐, 6‐, 10‐positions are slightly preferred in respect to the 3‐, 7‐, 9‐positions. In the case of the methylbullvalenes 8 and 9 methyl groups occupy additionally the 1‐, 2‐, 8‐ but not the 5‐position. Contrary to tetrabromobullvalenes 5 , isomers of 9 show no pronounced kinetic stability.