Fig. 2: Establishment of meta and para C−H difluoromethylation of pyridines.

a Choice of difluoromethylation reagent. b meta-functionalization. c para-functionalization. Yield of 5 was determined by 19F NMR using 1-bromo-4-fluorobenzene as the internal standard. E = CO2Me. EWG electron-withdrawing group, TMP 2,2,6,6-tetramethylpiperidine, CSA camphorsulfonic acid.