Arene-Metal Complexes. 12. Reaction of Substituted (Benzene)tricarbonylchromium Complexes with n-Butyllithium

Article abstract of DOI:10.1021/jo01301a002

Reaction of a series of substituted (benzene)tricarbonylchromium complexes with n-butyllithium has been examined.The reaction appears to proceed via proton abstraction to yield an (aryllithium)tricarbonylchromium intermediate which may then be quenched by the addition of primary alkyl halides,usually methyl iodide.New alkylated complexes may be obtained,or the material may be decomplexed to yield alkylated benzene derivatives.In this manner,(monoalkylbenzene)tricarbonylchromium complexes yield mainly m-dialkylbenzenes;(fluorobenzene)tricarbonylchromium yields o-fluorotoluene;(anisole)tricarbonylchromium yields mainly 2,6-dimethylanisole;and (N,N-dimethylaniline)tricarbonylchromium yields several isomeric N,N-dimethyltoluidines.(Iodobenzene)tricarbonylchromium undergoes metal-halogen exchange with n-butyllithium and may be converted to either toluene or n-butylbenzene depending on the reaction conditions.Comparison with known chemistry of the uncomplexed analogues demonstrates the strongly activating effect of the tricarbonylchromium moiety on these reactions.It is especially interesting that under these conditions reaction of (fluorobenzene)tricarbonylchromium with n-butyllithium results in proton abstraction rather than net nucleophilic displacement,as observed when less basic nucleophiles are used.