A Task-Specific Ionic-Liquid-Mediated Solvent-Free Protocol for Direct Access to Dimethyl Acetal Protected Benzimidazole 2-Carboxaldehydes

A robust and straightforward protocol has been developed for the synthesis of a diverse array of dimethyl acetal protected benz­imidazole-2-carboxaldehydes by reacting various 2-amino aniline derivatives with methyl 4,4-dimethoxy-3-oxobutanoate using the task-specific­ imidazolium ionic liquid (HBIm·TFA) as a promoter for N-C/C-N annulation processes. The present protocol offers several advantages over existing protocols, such as single-step process, short reaction times, very mild reaction conditions, high yields, ease of purification, recovery and reusability of the catalyst, and scale-up of the reaction.