Synthesis of 1,3-dihydro-2H-benzimidazol-2-ones (microreview)

The methodology for preparing domperidone: strategies, routes and reaction processes

Domperidone is a powerful peripheral dopamine receptor antagonist; however, a systematic review of the synthetic methods and processes of this drug has not been reported so far. This review summarizes the synthetic strategies, synthetic routes and reaction processes of domperidone in detail. Domperidone can be synthesized from the coupling reaction of two benzimidazolone derivatives (intermediates 1 and 2). Intermediate 1 can be prepared by two synthetic routes: the cyclization of o-phenylenediamine with carbonyl reagents followed by coupling with 1,3-dihalopropane, and the coupling reaction of o-halo or o-amino substituted nitrobenzene with 1,3-disubstituted propane followed by reduction and cyclization. The latter route avoids the production of di-substituted by-products and has higher reaction selectivity. Intermediate 2 is synthesized by coupling substituted nitrobenzene with 4-aminopiperidine followed by reduction and cyclization, which is similar to the synthetic route of intermediate 1. Understanding the advantages and drawbacks of these synthetic methodologies would provide insights for the development of new strategies to prepare domperidone. Moreover, the methods used to synthesize domperidone can provide alternative approaches in the preparation of drugs or compounds with similar structure.

Optimisation by Design of Experiment of Benzimidazol-2-One Synthesis under Flow Conditions

A novel flow-based approach for the preparation of benzimidazol-2-one (1) scaffold by the 1,1′-carbonyldiimidazole (CDI)-promoted cyclocarbonylation of o-phenylenediamine (2) is reported. Starting from a preliminary batch screening, the model reaction was successfully translated under flow conditions and optimised by means of design of experiment (DoE). The method allowed the efficient preparation of this privileged scaffold and to set up a general protocol for the multigram-scale preparation in high yield, purity, and productivity, and was successfully applied for the multigram flow synthesis of N-(2-chlorobenzyl)-5-cyano-benzimidazol-2-one, which is a key synthon for hit-to-lead explorations in our anti-inflammatory drug discovery program.