Synthesis of Α‐imino Amidines and 2,3‐diamino Indolenines Using a One‐Pot Graphene Oxide‐Catalyzed Process

The acid-catalyzed three-component (3 C) UGI reaction of isocyanides, amines, and aldehydes generally gives alpha-amino amidines. Herein, we report the graphene oxide (GO)-promoted promoted 3 C Ugi reaction followed by a C-N bond oxidation to provide rapid access to alpha-imino amidines. GO plays a crucial role both in the multicomponent reaction and in the subsequent oxidation. Interestingly, alpha-imino amidines bearing electron-donating groups undergo spontaneous cyclization leading substituted 2,3-diamino indolenines. The scope of the process has been investigated with respect to all three components, and a comparison between the one-pot and sequential approaches is given. The major advantages of the developed methodology include one-pot synthesis, operational simplicity, high atom economy, broad substrate scope, multicomponent character, and applicability towards gram scale synthesis. Recovery and regeneration of GO and investigation of its real active sites has been performed by control experiments and X-ray photoelectron spectroscopy (XPS).