Rearrangement with the formation of dimethyl 3,α-dimethyl-6-methylminofulvene-2,4-dicarboxylate occurs readily when dimethyl 1,2,7-trimethyl-1H-azepine-3,6-dicarboxylate is heated under reflux in benzene, or when dimethyl 4-chloromethyl-1,4-dihydro-1,2,6-trimethylpyridine-3,5-dicarboxylate is heated in mesitylene in the presence of barium carbonate. Other examples of this rearrangement are described and the structures of the fulvenes are supported by the interpretation of their mass spectral fragmentation patterns. 2,4-Diacetyl-α-hydroxy-3,α-dimethylfulvene is formed by the acid hydrolysis of the rearrangement product of 3,5-diacetyl-4-chloromethyl-1,4-dihydro-1,2,6-trimethylpyridine and has also been prepared by the progressive acetylation of sodium methyl-cyclopentadienide.