Pd-Catalyzed Tandem Approach for 1,2,3-Triazolo-azepine Fused Benzosuberenes and 1,2,3-Triazolobenzazepines Synthesis

Herein, a highly efficient palladium-catalyzed tandem approach for the synthesis of 1,2,3-triazolo-azepine-fused benzosuberenes (TAABS) has been developed for the first time with vinyl bromide and internal alkynes as starting precursors. The given reaction proceeded under ligand- and additive-free conditions via sequential carbopalladation, followed by intramolecular electrophilic substitution. Also, the developed protocol has good functional group tolerance, wherein a range of sterically hindered TAABS analogues has been synthesized in appreciable yields. In addition, the developed methodology was also extended for the synthesis of 1,2.3-triazolobenzazepines from triazole-bearing aryl iodides and internal alkynes. The present protocol operates under relatively milder conditions with comparatively shorter reaction time. Furthermore, computational studies were also performed to validate the proposed mechanistic pathways. Additionally, the developed protocol is applicable to the gram-scale synthesis of TAABS analogues.