Tandem Intramolecular Carbolithiation-Lithium / Zinc Transmetallation: A Synthetically Versatile Combination

The carbolithiation of 1-lithiohex-5-ene (2) gives cyclopentylmethyllithium (3), which after treatment with zinc dibromide yields a solution of the corresponding organozinc reagent (5). The palladium(II)-catalysed acylation of this compound with several acyl chlorides yields the expected ketones (6). By a copper(I)-promoted reaction of compound (5) with different allylic or propargylic chlorides or bromides, a very clean SN2' reaction takes place giving the expected olefins (7) or allenes (8), respectively. The palladium(II)-catalysed arylation of intermediate (5) with different aryl bromides or iodides affords the corresponding substituted arenes (9). Finally, the copper(I)-promoted conjugate addition of compound (5) to some α,β-unsaturated ketones gives the expected ketones (10), without any contamination of the corresponding 1,2-adducts.