Cyclopentadienes, fulvenes, and fulvalenes. Part IV. 1,2-Diphenylcyclopentadienes

Abstract

Attempts to obtain 1,2-diphenylcyclopentadiene led to its Diels–Alder dimer. Evidence for dissociation of this dimer has only been obtained in its reaction with molybdenum carbonyl. By contrast, 1,4-dimethyl-2,3-diphenylcyclopentadiene and 1,2,3-trimethyl-4,5-diphenylcyclopentadiene exist as stable monomers, like all other di-and polyarylcyclopentadienes. Exact structures have been assigned to these and other arylcyclopentadienes as well as several related cyclopentene derivatives on the basis of their n.m.r. spectra.