Synthesis of N-alkoxybenzimidazoles with differentiated C2 and O-substituents

N-Alkoxy-, N-aryloxy- and N-allyloxybenzimidazoles (prepared using tandem N-alkylation, heterocyclisation and O-alkylation with in situ alkylating agent) can be selectively O-deprotected and then independently realkylated to provide a protocol for diversification with differentiated substituents at C2 and on oxygen. In addition, carboxamide functionalised derivatives 8 are amenable to staged interruption of the tandem reaction, allowing sequential additions of two different bases and alkylating agents directly affording 9. This ‘start–stop–start’ tandem process also facilitates diversification to analogues bearing different C2 and N-alkoxy substituents.