Synthesis Of Fused 1,2,4-Triazoles Via I₂/KI-Mediated Oxidative N-N Bond Formation

Fused triazoles are an important class of nitrogen-containing heterocyclic compounds. In particular, the 1,2,4-triazolo[1,5-a]pyridine framework widely exists in the structures of many bioactive molecules, its derivatives have important applications in areas, such as, pharmceuticals and agricultural science. Therefore, there has been long-standing interest in their synthesis.N-N bond formation reaction is a valuable tool for the construction of nitrogen-containing heterocyclic frameworks. So far, intramolecular N-N bond formation reactions are rarely reported. Current methods are mainly in two aspects: transition-metal-catalyzed oxidations and hypervalent iodine-mediated oxidative cyclizations. Thus, development of new N-N bond formation reaction will be of great importance for the synthesis of nitrogen-containing heterocycles.In this dissertation, for the first time, we developped intramolecular N-N bond formation reaction by employing moleuclar iodine as the oxidant to prepare 1,2,4-triazolo[1,5-a]pyridines. Twenty-four 1,2,4-triazolo[1,5-a]pyridines and related heterocyclic deratives have been synthesized in 60%-95% yields via I2/KI-mediated oxidative cyclization of N-arylamidines in the presence of potassium carbonate as base. The advantages of this synthetic methodology include eviromental friendliness, short reaction time, high efficiency, broad substrate scope, and scalable synthesis.