New Gilman-type lithium cuprate from a copper(II) salt: synthesis and deprotonative cupration of aromatics

Deprotonative cupration of aromatics including heterocycles (anisole, 1,4-dimethoxybenzene, thiophene, furan, 2-fluoropyridine, 2-chloropyridine, 2-bromopyridine, and 2,4-dimethoxypyrimidine) was realized in tetrahydrofuran at room temperature using the Gilman-type amido-cuprate (TMP)₂CuLi in situ prepared from CuCl₂·TMEDA through successive addition of 1 equiv of butyllithium and 2 equiv of LiTMP. The intermediate lithium (hetero)arylcuprates were evidenced by trapping with iodine, allyl bromide, methyl iodide, and benzoyl chlorides, the latter giving the best results. Symmetrical dimers were also prepared from lithium azine and diazine cuprates using nitrobenzene as an oxidative agent.