Synthesis of Cyclooctatetraenes through a Palladium‐Catalyzed Cascade Reaction

Abstract

Reported is a cascade reaction leading to fully substituted cyclooctatetraenes. This unexpected transformation likely proceeds through a unique 8π electrocyclization reaction of a ene triyne. DFT computations provide the mechanistic basis of this surprizing reaction.

Molecular Diversity of Cyclooctatetraenes through Palladium‐Catalyzed Cascade Reactions

“…In this context, we recently reported a cascade sequence including cyclocarbopalladations [5] that provides facile access to fully substituted COTs 2 from alkenyl bromides 1 and a stannane as coupling partner (Scheme 1). [6] During this process, an aromatic side product 3 was also formed through an alternative competitive pathway. The proposed mechanism starts with two cyclocarbopalladations, first a 4-exo-dig and then a 5-exo-dig, providing intermediate 4.…”

“…A challenge in the field is the synthesis of fully substituted, unsymmetrical COTs with structural complexity. In this context, we recently reported a cascade sequence including cyclocarbopalladations that provides facile access to fully substituted COTs 2 from alkenyl bromides 1 and a stannane as coupling partner (Scheme ) . During this process, an aromatic side product 3 was also formed through an alternative competitive pathway.…”

Intramolecular trans‐Dicarbofunctionalization of Alkynes by a Formal anti‐Carbopalladation/Stille Cascade

“…Since the attack of the organopalladium species [Pd]‐R commonly takes place in a syn ‐fashion, Pd and R are located on the same side of the emerging double bond . Embedded in domino reactions, syn ‐carbopalladations of alkyne units have paved the way to a variety of (oligo)cyclic compounds such as steroid‐like scaffolds, chromanes, fenestranes, pentafulvalenes, molecular switches, truncated helicenes, persubstituted cyclooctatetraenes, hetero‐ and spirocycles, and several natural products…”

Intramolecular Pd‐Catalyzed Formal anti‐Carboalkoxylation of Alkynes: Access to Tetrasubstituted Enol Ethers

“…Initially, carbopalladation reactions of alkynes were integrated in cascades (domino processes) leading to steroid derivatives and highly substituted arenes . Recently, novel domino processes with one or several carbopalladations as key reactions have been designed affording highly complex natural products or natural product analogs, and also other more specific targets such as spirocycles, (oligo)cyclic compounds, dibenzopentafulvalenes, helical oligoenes, fenestranes, persubstituted cyclooctatetraenes, and molecular switches . Because the emerging organopalladium species, which is formed at the beginning of such a cascade, commonly attacks the carbon–carbon triple bond in a syn ‐fashion, both residues are located at the same side of the newly generated double bond…”