Hydrogenation of hexamethylbicyclo[2.2.0]hexa‐2,5‐diene (hexamethyldewarbenzene)

Hexamethylbicyclo[2.2.0]hexa‐2,5‐diene can be hydrogenated nearly quantitatively, with preservation of the bicyclic structure, to either the dihydro or the tetrahydro compound, depending on the reaction conditions. In both hydrogenation products the hydrogens are located in the exo position, as revealed by NMR spectroscopy. The corresponding dideutero compound was also prepared. Thermal isomerization of the dihydro product yields cis ‐1,2,3,4,5,6‐hexamethylcyclohexa‐1,3‐diene quantitatively.