Facile access to imidazole derivatives: carboxylic acids and δ-lactones

Abstract The nucleophilic addition of bis-(TMS)ketene acetals to doubly N -activated imidazole under mild conditions, leads to their corresponding dihydroimidazolyl carboxylic acids in a first instance. Subsequent reaction of these acids can be efficiently turned into new bicyclic δ-lactones by a regioselective ring closing procedure promoted by a NBS. Along the work presented herein, the effectiveness of bis-(TMS)ketene acetals as 1,3-carbon-oxygen dinucleophiles was confirmed in this type of reactions, expanding thus the range of aza-compounds with bicyclic frameworks capable of being built.