Reactions of acyclic ketones and o-phenylenediamines under solvent- and catalyst-free conditions have been developed for the preparation of dihydrobenzimidazoles. This method can also be used for the synthesis of other heterocyclic compounds such as dihydrobenzothiazoles and perimidines.
![Graphical abstract: Solvent- and catalyst-free synthesis of 2,3-dihydro-1H-benzo[d]imidazoles](http://hg.y866.cn/compound/lib/scimg/usr/1/C0GC00572J.jpg)
