Assembly of Indolo[2,1- a ]isoquinolines via a C–H Oxidation/Carbene Insertion Cascade

A metal-free synthesis of indolo[2,1-a]isoquinolines is achieved via a one-pot C-H oxidation/intramolecular carbene insertion cascade. The strategy employs CBr₄ as a mild oxidant and diazoacetates to form key α-diazo intermediates, which undergo visible-light-induced denitrogenative cyclization to forge the target framework. This protocol features operational simplicity, excellent functional group tolerance, and scalability, enabling the discovery of derivatives with aggregation-induced emission properties.