Synthesis of 2-Fluoroalkylated Pyridines and Fluoropyridines by Thermal Denitrogenation of N -Fluoroalkyl-1,2,3-triazoles and Cyclization of Ketenimines

2-Fluoro-6-fluoroalkylpyridines and their ring-fused analogues were synthesized from N-fluoroalkyl-4-alkenyl-1,2,3-triazoles by thermal denitrogenation, fluorine shift, cyclization, and hydrogen fluoride elimination. This reaction proceeds via ketenimine intermediates. Conversely, 2-fluoroalkylpyridines were prepared starting from N-fluoroalkyl-4-alkyl-1,2,3-triazoles and proceeded by denitrogenation, fluorine shift, hydride shift, cyclization, and hydrogen fluoride elimination. Nucleophilic aromatic substitution of 2-fluoro-6-fluoroalkylpyridines afforded highly functionalized 2-fluoroalkylpyridines.