THE REGIOSELECTIVE ACYLATION REACTIONS OF IMIDAZOPYRIDINES

The regioselectivity of acylation in imidazopyridines can be controlle d by two mechanism-specific reactions. As expected acylation reactions under Friedel-Crafts conditions result in reaction at the most electr on-rich site in imidazopyridines. However, depending on the structure of the imidazopyridine, ylid intermediates are proposed to direct reac tion to the electron-deficient site in the parent heterocycles. These observations led to the selective synthesis of acylimidazopyridines an d this methodology was used in the preparation of analogs of the alpha (2)-adrenergic agonists MPV-207 and clonidine.