A Straightforward, One-Pot Protocol for the Synthesis of Fused3-Aminotriazoles

摘要

A simple protocol for the synthesis of 3-amino-[1,2,4]triazolo[4,3-a]pyridines is reported. The newlydeveloped one-pot methodology involves the reaction of hydrazinopyridine with isothiocyanates to givethe corresponding thiosemicarbazides, which are further desulfurized in situ using polymer-supportedMukaiyama's reagent to promote the final cyclization and formation of the central core. Aryl isothio-cyanates bearing both electron-donating and electron-withdrawing groups are well tolerated, and theexpected compounds were obtained in excellent purities and yields after removal of salts with a SPE-NH_2column. This methodology proved to be robust in the extension to 3-amino-[1,2,4]triazolo[4,3-a]pyrazinesand 3-amino-[1,2,4]triazolo[4,3-d-pyrimidines, and no significant differences were noticed in terms ofpurities and yields. The straightforward protocol developed, mix, filter, and evaporate, is appropriate forperforming multiple reactions in parallel fashion without need of purification.