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.

Chemoselective Transformations of Cyclic ß-Bromoacrylic Acids with Palladacycles Formed by Aryl Iodides to Access Fused or Spiro Polycycles.

A palladium-catalyzed chemoselective decarboxylative annulation of different aryl iodides with cyclic ß-bromoacrylic acids for the construction of interesting fused and spiro polycycles is disclosed. Notably, cyclic ß-bromoacrylic acids can chemoselectively act as C1 or C2 insertion units by the use of different aryl iodides. 2-Iodo-N-methacryloylbenzamides can undergo a Heck/[4+2] annulation to afford hexahydrodibenzoisoquinoline-4,6(5H)-diones. Employing 2-iodobiphenyls or N-(2-iodophenyl)-2-phenylacrylamides as substrates enables the assembly of spirofluorenes and dispirooxindoles.