Abstract A general and efficient Rh(III)-catalyzed ortho-C–H alkylation of 2-arylbenzothizazoles and 2-arylthiazoles with potassium alkyltrifluoroborates has been developed. The present method leads to the construction of a library of alkylated 2-arylbenzothiazoles and 2-arylthiazoles with yields up to 99%. A general and efficient Rh(III)-catalyzed ortho-C–H alkylation of 2-arylbenzothizazoles and