Rh(III)-catalysed site-selective alkylation of β-carbolines/isoquinolines and tandem C-H/C-N functionalization to construct indolizine-indole frameworks

The rhodium-catalysed ortho-selective carbenes insertion strategy to activate the non-acidic sp2 C-H bond of beta-carboline and isoquinoline scaffolds was developed. This transformation endows facile fabrication of C-C bond with high atom economy, pleasant yields and wide functional group tolerance exploiting directing properties of pyridinic nitrogen. In this protocol, diazo compounds of diethyl malonate, dimethyl dimedone and oxindole are tested as carbene source with the release of environmentally benign N2 gas as the by-product. Moreover, to perceive mechanistic insights, ESI-MS studies were conducted, and the key intermediates associated with this transformation were identified. In addition, the metal-free construction of planar polycyclic indolizine-indole frameworks has been accomplished from the synthesized products. Furthermore, the neoplastic and fluorescence properties of C-N annulated compounds were also determined.

Automated summary

The rhodium-catalysed carbenes insertion strategy was developed to activate the non-acidic C-H bond of beta-carboline and isoquinoline scaffolds, allowing for facile C-C bond formation with high atom economy and wide functional group tolerance. Mechanistic insights were obtained and polycyclic indolizine-indole frameworks were successfully constructed.