Evidence for cyclohexyne as an intermediate in the coupling of phenyllithium with 1-chlorocyclohexene

Elimination-Adition mechanisms involving "benzyne"-type (C_6H_4) intermediates have been established for the rearrangements which occur in the amination of non-activated aryl halides, high temperature alkaline hydrolysis of aryl halides and the coupling of phenyllithium with aryl halides. Wittig and Harboth have reported small yields of 1-phenylcyclohexene from the coupling of phenyllithium with 1-chlorocyclohexene and it appeared possible that this reaction might well proceed by way of cyclohexyne as an intermediate. Of interest in this connection is the report by Favorsky and Boshowsky that a cyclohyexne trimer (dodecahydrotriphenylene) is formed in the reaction of 1,2-dibromocyclohexene with sodium

Evidence for Cyclohexyne and Cyclopentyne as Intermediates in the Coupling Reactions of Phenyllithium with 1-Chlorocyclohexene and 1-Chlorocyclopentene

Phenyllithium and 1-chlorocyclohexene and 1-chlorocyclopentene react at 150º in ether to form 1-phenylcyclohexene and 1-phenylcyclopentene, respectively. A 1:1 mixture of 1-chlorocyclohexene-2-^(14) and 1-chlorocyclohexene-6 ^(14)- with phenyllithium yielded 1-phenylcyclohexene-x-^(14)C which contained 23 % of the ^(14)C label in the 1-position. When 1-chlorocyclopentene-1-^(14)C was heated with phenyllithium, extensive rearrangement of the ^(14)C label occurred with 48.9, 36.2, and 14.9% of the ^(14)C distributed in the 1-,2-, and 5-positions of 1-phenylcyclopentene, respectively. The observed ^(14)C rearrangements which accompanied these nucleophilic substitution reactions are best rationalized in terms of an elimination-addition mechanism involving cycloalkyne intermediates

Cycloadditions of Cyclohexynes and Cyclopentyne

[Image: see text] We report the strategic use of cyclohexyne and the more elusive intermediate, cyclopentyne, as a tool for the synthesis of new heterocyclic compounds. Experimental and computational studies of a 3-substituted cyclohexyne are also described. The observed regioselectivities are explained by the distortion/interaction model