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.
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