Lithiation of 2-chloro- and 2-methoxypyridine with lithium dialkylamides: initial ortho-direction or subsequent lithium ortho-stabilization?
The lithiation pathway of 2-chloro and 2-methoxypyridine with LDA and LTMP has been investigated using deuterated probes. The availability of both H-6 and H-3 protons on the pyridine nucleus was found to be critical to ensure complete C-3 lithiation. We thus concluded that the C-3 lithiation was not a straightforward process. A mechanism involving precomplexation of lithium dialkylamides near the H-6 proton and formation of a 3,6-dilithio pyridine intermediate is proposed.
Gros
Philippe
P
Synthèse Organique et Réactivité, UMR CNRS-UHP 7565, Faculté des Sciences, Université Henri Poincaré-NancyI, BP 239, 54506, Vandoeuvre-Lès-Nancy, France.
Choppin
Sabine
S
Fort
Yves
Y