Yield:-

Reaction Conditions:

with trichlorophosphate at 95; for 1.5 h;

Steps:

Typical experimental procedure for substituted 2-chloro-benzimidazol

General procedure: A mixture of 5-methyl-1,3-dihydrobenzimidazol-2-one (1.00 g, 6.84 mmol) and phosphorous oxychloride (9.54 mL, 103 mmol) was stirred for 1.5 h at 95 °C. After being cooled to ambient temperature, the reaction mixture was carefully added to a mixture of saturated NaHCO₃ aq. (60 mL) and ethyl acetate (60 mL). The separated organic layer was washed with water, brine, and dried over MgSO₄. After filtration, the filtrate was evaporated in vacuo, The resulting precipitates were collected by filtration, and successfully washed with isopropyl ether to give 2-chloro-5-methyl-benzimidazole (1.74 g, 58.9 %).

References:

Nakao, Syuhei;Mabuchi, Miyuki;Shimizu, Tadashi;Itoh, Yoshihiro;Takeuchi, Yuko;Ueda, Masahiro;Mizuno, Hiroaki;Shigi, Naoko;Ohshio, Ikumi;Jinguji, Kentaro;Ueda, Yuko;Yamamoto, Masatatsu;Furukawa, Tatsuhiko;Aoki, Shunji;Tsujikawa, Kazutake;Tanaka, Akito [Bioorganic and Medicinal Chemistry Letters,2014,vol. 24,# 4,p. 1071 - 1074] Location in patent:supporting information