Oxidative Cyclization of 4-(2-Mercaptophenyl)-Substituted 4H-1,2,4-Triazolium Species to Tricyclic Benzothiazolium Salts

Herein we report a generally applicable method for the preparation of N-substituted benzo[4,5]thiazolo[2,3-c][1,2,4]triazol-1-ium salts from air stable precursors. This transformation features selective deprotection of a para-methoxybenzyl protected thiol followed by C-H functionalization of the linked 1,2,4-triazolium salts under oxidative conditions. Using this procedure, we synthesized a variety of tricyclic thiazolium salts which contain both electron-withdrawing and electron-donating aromatic substituents as well as aliphatic substituents. Our approach also tolerates many functional groups including alkynes, alcohols, diols, amides, and polyethers.

Automated summary

Here, we report a generally applicable method for preparing N-substituted benzo[4,5]thiazolo[2,3-c][1,2,4]triazol-1-ium salts from air-stable precursors. This method involves the selective deprotection of a para-methoxybenzyl protected thiol, followed by C-H functionalization of the linked 1,2,4-triazolium salts under oxidative conditions. The synthesized tricyclic thiazolium salts can contain various electron-withdrawing and electron-donating aromatic substituents, as well as aliphatic substituents, and are tolerant to many functional groups.