Heptafulvene (methylenecycloheptatriene)

Abstract

Heptafulvene (Chart 2, I), a conjugated, non-benzenoid hydrocarbon of theoretical interest, has been synthesized by a Hofmann elimination on trimethyl 7-cycloheptatrienylmethyl ammonium iodide. Non-isolable, stable only in dilute solution, I is assigned the heptafulvene structure on the basis of catalytic hydrogenation to methylcycloheptane; indication of a methylene group from I. R. and ozonolysis to formaldehyde; association of elaborate visible and U. V. spectrum with a highly conjugated system; marked sensitivity to acid; and reaction with acetylene dicarboxylic ester to give (ultimately) an azulene derivative.