Direct and Regioselective Introduction of Acetals into Imidazoles at the 2‐Position by an Iridium‐Catalyzed Reaction with Formates in the Presence of Hydrosilanes

Abstract

The iridium‐catalyzed reaction of imidazoles with formates in the presence of hydrosilanes as coreactants led to the production of 2‐[(alkoxy)(siloxy)methyl]imidazoles. Dimethyl acetylenedicarboxylate was the additive of choice for the reaction in terms of reaction efficiency. No reaction was observed in the absence of the hydrosilanes. Whereas substituents at the 1‐ and 5‐positions on the imidazole ring did not affect the reaction, substituents at the 4‐position greatly retarded the reaction. The regioselective reaction of 1‐methyl‐1,2,4‐triazole occurred at the carbon atom between the sp3 and sp2 nitrogen atoms of the ring but not between two sp2 nitrogen atoms. The products were converted into imidazole 2‐carbaldehydes by hydrolysis under acidic conditions.