Efficient Synthesis of 9‐Aminophenanthrenes and Heterocyclic Analogues by Electrocyclization of Biaryl Keteniminium Salts

We describe herein a high yielding and metal‐free methodology to access 9‐aminophenanthrene derivatives and heterocyclic analogues starting from biaryl acetamides. The conversion of the substrates to their corresponding keteniminium salts triggers a spontaneous electrocyclization occurring at room temperature within a few minutes. DFT Calculations and competition reactions were carried out to rationalize the observed reactivity and understand the relative kinetics compared to other known reactions involving keteniminium salts.