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

A palladium-catalyzed divergent cascade decarboxylative annulation of aryl iodides and α-oxocarboxylic acids using norbornene (NBE) derivatives as a controlled switch is reported. When NBE is used as a mediator, fluorenones are synthesized with moderate to excellent yields via a Catellani reaction that involves sequential ortho -C-H arylation and ipso -decarboxylative acylation of aryl iodides. Employing oxanorbornadiene (ONBD) instead of NBE enables the assembly of dibenzo[ a , c ]cycloheptenones by a retro-Diels-Alder reaction rather than the release of an ONBD. Additionally, the synthetic utility of this method is demonstrated by the diversification of the products.