Tuning the Cyclopropane Ring-Opening Reaction over Electronic Bias by Fusion to a Pre-Aromatic Ring: TfOH-Promoted Aromatization of Dibenzonorcaradienes to Dibenzo[<i>f</i>,<i>h</i>]isocoumarins

Abstract

Fusion of the cyclopropane ring bearing two vicinal acceptors to the pre-aromatic dihydrophenanthrene ring, which is constructed by the Pd-catalyzed cross-coupling between the vicinal aromatic rings, is found to effectively direct the cleavage of the electronically unfavored cyclopropane bond between the vicinal acceptors. Consequently, a modular method for the rapid synthesis of dibenzo­[f,h]­isocoumarins from methyl ketones, aryl aldehydes, and α-keto esters via a reaction cascade of aldol condensation, Kukhtin–Ramirez cyclopropanation, Pd-catalyzed direct arylation, and acid-promoted aromatization has been realized