Synthesis of Benzo[4,5]thiazolo[2,3-c][1,2,4]triazole Derivatives via C-H Bond Functionalization of Disulfide Intermediates.

Many nitrogen- and sulfur-containing heterocyclic compounds exhibit biological activity. Among these heterocycles are benzo[4,5]thiazolo[2,3-c][1,2,4]triazoles for which two main synthetic approaches exist. Here we report a new synthetic protocol that allows the preparation of these tricyclic compounds via the oxidation of a mercaptophenyl moiety to its corresponding disulfide. Subsequent C-H bond functionalization is thought to enable an intramolecular ring closure, thus forming the desired benzo[4,5]thiazolo[2,3-c][1,2,4]triazole. This method combines a high functional group tolerance with short reaction times and good to excellent yields.

Catalytic Preparation of 1-Aryl-Substituted 1,2,4-Triazolium Salts.

1,4-Diaryl- and 1-aryl-4-alkyl-substituted 1,2,4-triazolium salts are convenient air-stable precursors to carbenes used both as organocatalysts or as ligands for transition metal complexes. Traditionally, they are prepared via a multistep synthetic pathway with the low-yielding formation of the triazolium ring occurring in the last step. We have developed an alternative two-step synthesis involving the conversion of a primary amine or aniline derivative to the corresponding 4-substituted triazole followed by a copper-catalyzed arylation with diaryliodonium salts. This transition metal-catalyzed arylation can be carried out under mild conditions in acetonitrile and is tolerant toward both water and oxygen. Additionally, the high functional group tolerance of the protocol described here gives easy access to triazolium salts containing heterocyclic substituents or sulfides.