Lithiation of 2-heterosubstituted pyridines with BuLi-LiDMAE: evidence for regiospecificity at C-6.
The determination of the initial deprotonation site of 2-chloro- and 2-methoxypyridine during reaction with BuLi-LiDMAE has been investigated. A series of experiments on deuterated regioisomers revealed a direct lithiation at C-6 excluding a potential first classical ortholithiation and lithium equilibration in the reaction medium. These results suggested that the formation of lithium aggregates at the neighboring of the pyridinic nitrogen atom favored BuLi delivery at C-6 as well as 6-lithio intermediate stabilization.
Gros
Philippe
P
Synthèse Organique et Réactivité, UMR CNRS-UHP 7565, Faculté des Sciences, Université Henri Poincaré-Nancy I, BP 239, 54506 Vandoeuvre-Les-Nancy, France.
Choppin
Sabine
S
Mathieu
Julien
J
Fort
Yves
Y