Résumé
The n-BuLi and lithium 2,2,6,6-tetramethylpiperidine (LTMP) metalation of imidazo[1,2-a]pyrazine heterocycles and subsequent quenching with electrophiles is described. Bromine atoms exhibit different behaviours towards lithiation depending on their positions (3 or 6) on the imidazo[1,2-a]pyrazine heterocycle. Halogen-metal exchange occurs readily with the bromine on position 3. On the contrary, bromine on position 6 only leads to C-5 substituted derivatives further to an ortho-directing effect.
The n-BuLi and LTMP metalation and halogen-metal exchange of imidazo[1,2-a]pyrazine heterocycles followed by subsequent quenching with electrophiles are described.