A novel annulation reaction of N-substituted-2-nitrosoanilines with esters of α-isocyano acids. A one-pot, two-step route to 2-benzimidazole-substituted esters of α-amino acids

A BF3-promoted α-addition of isocyanides to both nitrogen atoms of N-aryl-2-nitrosoanilines leads to stable BF3-complexes of 3-N-hydroxy-(2-alkylimino)benzimidazole derivatives, which, after reduction with Zn in AcOH produce 1-N-aryl-2-alkylaminobenzimidazoles. This two-step annulation proceeds efficiently in a one-pot protocol with isocyanides derived from esters of α-amino acids. The chirality of the latter remains unaffected in the reaction.