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.

Advances in Palladium‐Catalyzed Cascade Cyclizations

“…In 2016, Suffert and co-workers reported the synthesis of cyclooctatetraenes 209 via multiplec arbopalladations,e lectrocyclization, andt ermination by a Stille coupling (Scheme 62). [86] Especially the proposed initial 4-exo-dig carbopalladationt of orm bicycle[4.2.0]octane 210 is remarkable and exceedingly rare in palladium-catalyzed cascade reactions.T he cascade is continued by a5 -exo-dig carbopalladation, yieldingalkenyl-Pd(II) species 211.…”

Alkyne Aminopalladation/Heck and Suzuki Cascades: An Approach to Tetrasubstituted Enamines

“…Such carbopalladation cascades using C�C triple bonds have been developed by many groups during recent decades. [6] These transformations have paved the way to unusual molecular architectures such as helicenes, [2,3,7] fenestranes, [8] highly substituted cyclooctatetraenes [9] and molecular switches; [10] natural products [11] have also proved accessible in a quick and facile fashion.…”

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

“…Dicarbofunctionalizations of internal alkynes by the addition of two carbon moietiest oac arbon-carbon triple bond have paved the way to numerous products with embeddedt etrasubstituted alkene units.F or this purpose, several transitionmetal-catalyzed approaches have been developed;i np articular,P dc atalysis has proved av ery powerful method.I nitially, carbopalladation reactions of alkynes were integrated in cascades (domino processes) [1] leading to steroid derivatives and highly substituted arenes. [2,3] Recently,n ovel domino processes with one or several carbopalladationsa sk ey reactions have been designed affording highly complex natural products or natural product analogs, [4] and also other more specific targets such as spirocycles, [5] (oligo)cyclic compounds, [6] dibenzopentafulvalenes, [7] helical oligoenes, [8] fenestranes, [9] persubstituted cyclooctatetraenes, [10] and molecular switches. [11] Because the emerging organopalladium species, which is formed at the beginningo fs uch ac ascade,c ommonly attackst he carboncarbon triple bond in a syn-fashion, both residues are located at the same side of the newly generated double bond.…”