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Note | Regular issue | Vol 48, No. 5, 1998, pp.1015-1022
Published online, 1st January, 1970
DOI: 10.3987/COM-98-8124
The Regioselective Acylation Reactions of Imidazopyridines

Dennis J. Hlasta* and Marla J. Silbernagel

*Department of Medicinal Chemistry, Sanofi Winthrop Inc., Collegeville, Pennsylvania, 19426, U.S.A.


The regioselectivity of acylation in imidazopyridines can be controlled by two mechanism-specific reactions. As expected acylation reactions under Friedel-Crafts conditions result in reaction at the most electron-rich site in imidazopyridines. However, depending on the structure of the imidazopyridine, ylid intermediates are proposed to direct reaction to the electron-deficient site in the parent heterocycles. These observations led to the selective synthesis of acylimidazopyridines and this methodology was used in the preparation of analogs of the α2-adrenergic agonists MPV-207 and clonidine.