afford functionalized organometallic compounds of Mg, Zn, or Cu. This in situ trapping method allows an expedited metalation (−78 °C, 5 min) of a range of sensitive pyridines (bearing a nitro, ester, or cyano group) and allows the preparation of kinetic regioisomers of functionalized aromatic compounds or heterocycles not otherwise available by standard metalating agents, such as TMPMgCl⋅LiCl or TMPZnCl⋅LiCl
iodine-magnesium exchange. In many cases, the exchange can be extended to heteroaryl bromides, and a case of a chlorine-magnesium exchange is described with tetrachlorothiophene. This new preparation of functionalized heteroarylmagnesium compounds provides after reaction with various electrophiles a new entry to a broad range of polyfunctional pyridines, imidazoles, furanes, thiophenes, pyrroles, antipyrines
Functionalized iodopyridines bearing either a chloride, ester or nitrile function were converted to the corresponding organomagnesium derivatives at -40 °C or -78 °C by treatment with i-PrMgBr (1.1 equiv, 0.5 h, > 90% yield). The resulting functionalized Grignard reagents react with aldehydes, TosCN directly or with allylic bromides and benzoyl chloride after transmetalation with CuCN leading to polyfunctional pyridines.
salts of 2-, 3- and 4-pyridinecarboxylic acids undergo deprotonation at the position adjacent to the carboxylate group when treated with LTMP in THF at 0 °C, −50 °C and −25 °C, respectively. The lithiation conditions could be extended to chloronicotinic acids, and even to an activated benzoic acid.