Rhodium-Catalyzed One-Pot Access to N‑Polycyclic Aromatic Hydrocarbons from Aryl Ketones through Triple C–H Bond Activations

A Rh-catalyzed pot and step economic
synthesis of aza-polycyclic
aromatic hydrocarbons (N-PAHs) from readily available aryl ketones
and alkynes has been disclosed. Additionally, a novel synthetic application
of the well-known aminating reagent hydroxylamine-O-sulfonic acid (HOSA) has been explored as an in situ redox-neutral
directing group for the formation of N-PAHs via isoquinoline. Multiple
bond formation in a single operation through a cascade of triple C–H
bond activations is the beauty of this protocol. The challenging annulations
of two different alkynes in a regioselective fashion have been demonstrated
effectively. Mechanistic studies reveal that 3,4-diphenyl-1-methylisoquinoline
is an active intermediate for this one-pot transformation.