Gold-catalyzed C-H Functionalization of Phenothiazines with Aryldiazoacetates

Phenothiazine is an important structural motif in pharmaceuticals and advanced functional organic materials. However, the C-H functionalization reaction of N-protected phenothiazine is rather unexplored and often shadowed by its chemical reactivity on the heteroatomic centers, which limits the diversity of its potential applications. This report demonstrates a straightforward approach towards the site-selective C-H functionalization of phenothiazine at the para-position of N atom via gold-catalyzed carbene transfer reactions (37 examples, up to 83% yield). The mechanism behind the regionselectivity of the C-H functionalization reaction was also elucidated by a combination of computational and experimental studies.