Evidence for Cyclopentyne as a Reaction Intermediate in the Coupling of Phenyllithium with 1-Chlorocyclopentene

Evidence has been presented previously for the intervention of benzyne and cyclohexyne as intermediates in nucleophilic substitution reactions of phenyl and cyclohexenyl halides, respectively. In studies designed to determine the minimum ring size for operation of the elimination-addition mechanism, we have now found that an entity with the symmetry properties of cyclopentyne must be involved in the formation of 1-phenylcyclopentene from 1-chlorocyclopentene-1-^(14)C and phenyllithium.