Abstract The sodium salts of the tricyclic tosylhydrazones 1, 4 and 5 yield by base-catalyzed fragmentation between 130–160 the monocyclic ring expansion products 2, 3 and 6. IR.- spectrometry suggests a diazoalkane A as the principal intermediate of the fragmentation. Besides the known carbene mechanism the reaction is considered to pass through a noncarbenoid intermediate.
