Base/Solvent Controlled Divergent Synthesis of Norbornane-Fused Dihydrophenanthrenes and Triphenylenes via Palladium Catalyst

Abstract

A base/solvent controlled divergent synthesis for the construction of polycyclic hydrocarbons has been developed. In this process, norbornene through a reagent role leads to the synthesis of norbornane-fused dihydrophenanthrenes, which are essential due to their biological activities. Amazingly, by switching solvent and base, the role of norbornene becomes limited to a mediator/catalyst; therefore, it is removed from the final scaffold, and triphenylenes are regioselectively synthesized. Additionally, by removing norbornene from the reaction conditions, a different path leading to synthesis of unsymmetrically substituted triphenylenes with exceptional regioselectivity is established. This reaction includes a rare domino decarboxylation/C−H activation/annulation in a chemo-and regioselective manner.

Norbornene Derivatives-Controlled Palladium-Catalyzed Divergent Synthesis of Dibenzo[a,c]cycloheptenones and Fluorenones from Aryl Iodides and α-Oxocarboxylic Acids

“…In the reaction, the aryl norbornyl palladacycle formed by an oxidative addition/norbornene (NBE) insertion/C–H bond activation sequence is the key intermediate. Recently, Kwong et al and our group found that the palladacycle formed by Catellani strategy could be captured by o -bromobenzoic acids to give phenanthrenes and triphenylenes. , Since then, a series of decarboxylative cyclization reactions were reported by us and others via a carboxyl-assisted palladacycle capture strategy, which provide an efficient platform for the synthesis of polycyclic compounds. Despite great progress, the application of α-oxocarboxylic acids in the Catellani reaction has not been reported yet.…”