Transition-metal-catalyzed site-selective C7-functionalization of indoles: advancement and future prospects

C7-Decorated indoles are important structural motifs present in a plethora of bioactive and pharmaceutical compounds. Early stage developments for C7 modifications were realized through directed metallation (DOM) and subsequent quenching with suitable electrophiles or by halogenation with Cu( ii ) halides. Direct C-7 functionalization of indoles is comparatively difficult compared to functionalization at C-2 and C-3 positions owing to the inherent reactivity of the pyrrole-type ring. However, recently transition-metal-catalyzed auxiliary assisted site-selective C-7 functionalization of indoles has emerged as an elegant synthetic tool for carbon-carbon and carbon-heteroatom bond formation to diversify the indoles. This article covers the advancement, application and mechanistic underpinnings of the evolved transformations of the otherwise inert C7-H bond up to October 2018. The advancement and future prospects of transition-metal-catalyzed auxiliary assisted regioselective C7-functionalization of indoles/indolines are covered in this article.