Lithiation of Heterocycles Directed by α-Amino Alkoxides

Article abstract of DOI:10.1021/jo00377a019

The addition of heterocyclic aromatic aldehydes to certain lithium dialkylamides gave α-amino alkoxides that were ring-lithiated with butyllithium.Alkylation and hydrolysis provided ring-substituted heterocyclic aromatic aldehydes via a one-pot reaction.The metalation of α-amino alkoxides derived from thiophenecarboxaldehydes, furaldehydes, N-methylpyrrolecarboxaldehydes, and indolecarboxaldehydes was examined.The regioselectivity of the lithiation, was dependent on the heterocycle, the amine component of the α-amino alkoxide, and the metalation conditions.A novel N-methyl metalation of α-amino alkoxides derived from N-methylpyrrole-2-carboxaldehyde and N-methylindole-2-carboxaldehyde was achieved when N,N,N'-trimethylethylenediamine was used as the amine component for in situ formation of the α-amino alkoxides.The novel directed N-methyl lithiations are attributed to an intramolecular TMEDA-like assisted metalation.