(Z)-N'-(1H-Benzo[d]imidazol-2-Yl)-Arylimidamide Adducts of 2-Aminobenzimidazole and Aromatic Nitriles: Structural and Spectroscopic Proof of Regiochemical and Stereochemical Outcomes

The selection of a core scaffold or template is of enormous importance in medicinal chemistry. Benzimidazoles are a recurring fragment in medicinal chemistry, and the 2-amino derivative is a versatile example in lead generation. Alkylated and acylated examples abound, however, alternative linkage chemistries leading do more diverse structures are needed.
Here we discuss the regiochemistry of nucleophilic addition of 2-aminobenzimidazole to nitriles, leading to imidamide (amidine) adducts. Additionally, we use extensive NMR analysis and ultimately X-ray crystallography to demonstrate both the regiochemistry and stereochemistry of the addition products, arising from derivatisation of the exocylic 2-amino group.