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

Palladium/norbornene-catalyzed C-H/N-H cycloaddition of carbazoles with 2-halobenzoic acid derivatives

An example of palladium/norbornene-catalyzed C-H/N-H cycloaddition of carbazoles with 2-bromobenzoic acids is presented, in which a collection of important carbazoles is expeditiously obtained. Derivatives, including acyl halides, α-oxocarboxylic acids, anhydrides, and even amides, are all allowed. Preliminary mechanistic studies reveal that a rare six-membered spiropalladacycle is involved.

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.