Mechanistic insights into an NHOAc-promoted imine dance in Rh-catalysed multicomponent double C-H annulations through an N-retention/exchange dual channel.

Developing new and understanding multicomponent reactions (MCRs) is an appealing but challenging task. Herein, Rh(iii)-catalyzed multicomponent double C-H annulations of cyclic diimines (or diketones and acetone), alkynes, and ammonium acetate to assemble functionalized 1,1'-biisoquinolines and C-bridged 1,1'-bisisoquinolines with controllable N/N editing in one shot has been developed. Through a combination of isotopic-labeling (H, O, and N) experiments, crystallography, and time-dependent ESI-MS, the reaction process was studied in detail.