Annulative π-Extension by Rhodium(III)-Catalyzed Ketone-Directed C-H Activation: Rapid Access to Pyrenes and Related Polycyclic Aromatic Hydrocarbons (PAHs)

Annulative pi-extension (APEX) reaction has become a powerful tool for the precise synthesis of well-defined polycyclic aromatic hydrocarbons (PAHs) such as nanographene, graphene, and other PAHs possessing unique structure. Herein, an APEX reaction has been realized at the masked bay-region for the efficient and rapid synthesis of valuable PAH, pyrene, bearing substitutions at the most challenging K-region. Rh-III-catalyzed ketone-directed C-H activation at the peri-position of a naphthyl-derived ketone, alkyne-insertion, intramolecular nucleophilic attack at the carbonyl-group, dehydration, and aromatization steps occurred in one-pot to effectuate the protocol. Employing this strategy, a two-fold APEX reaction on enantiopure BINOL-derived ketones provided access to axially-chiral bipyrene derivatives. The detailed DFT study to support proposed mechanism, and synthesis of helical PAHs like dipyrenothiophene and dipyrenofuran are other highlights of the present study.

Automated summary

Annulative pi-extension (APEX) reaction is a precise synthesis method for polycyclic aromatic hydrocarbons (PAHs) such as nanographene and graphene. In this study, a masked bay-region APEX reaction was successfully used to efficiently synthesize valuable PAH pyrene with substitutions at the challenging K-region. The reaction involved Rh-III-catalyzed C-H activation, alkyne-insertion, intramolecular nucleophilic attack, dehydration, and aromatization steps.