Access to <i>N</i>‑Thioalkenyl and <i>N</i>‑(<i>o</i>‑Thio)aryl-benzimidazol-2-ones by Ring Opening of Thiazolobenzimidazolium and Benzimidazobenzothiazolium Salts and C–O Bond Cleavage of an Alkoxide

We report herein the synthesis of highly functionalized 1,3-dihydro-2H-benzimidazol-2-ones via a ring opening of thiazolo­[3,2-a]­benzimidazolium or benzimidazo­[2,1-b]­[1,3]­benzothiazol-6-ium salts and an unusual C–O bond cleavage of an alkoxide. A large variety of benzimidazolones bearing an original N-thioalkenyl or N-(o-thio)­aryl group was obtained in high yields. The developed chemistry provides efficient and rapid access to the privileged benzimidazol-2-one scaffold.