Palladium(II)‐Catalyzed Decarboxylative Heck Arylations of Acyclic Electron‐Rich Olefins with Internal Selectivity

Abstract

Despite the recent emergence of decarboxylative CC bond forming reactions, methodologies providing internally arylated electron‐rich olefins are still lacking. We herein report on palladium(II)‐catalyzed decarboxylative Heck arylations of linear electron‐rich olefins with excellent selectivity for the internal position. The method allows a variety of electron‐rich linear olefins to undergo arylation with ortho‐functionalized aromatic carboxylic acids, including heterocycles. The reaction mechanism has been explored with ESI‐MS studies to confirm previous findings, and to reveal the formation of a highly stable palladium complex as a result of the Heck product reacting with the catalyst.

Reversible Insertion of Carbon Dioxide at Phosphine Sulfonamido PdII–Aryl Complexes

“…44 Although the protonation step is effectively performed by the aromatic carboxylic acids, stoichiometric decarboxylative coupling of 2,6-dimethoxybenzoic acid with styrene could be observed, selectively yielding 1,3-dimethoxy-2-(1-phenylvinyl)benzene (Scheme 6). This rather exclusive 45 regioselectivity to 1,1-disubstituted olefins is likely caused by the steric bulk of the ligand's N-aryl moiety, forcing styrene coordination in a manner only allowing a 2,1-insertion mechanism.…”

Aryl-Decarboxylation Reactions Catalyzed by Palladium: Scope and Mechanism

“…In a contemporaneous study, Larhed and co-workers demonstrated that electron-rich alkenes, enamides, and enol ethers, can undergo a similar decarboxylative Heck reaction using benzoquinone (BQ) as the stoichiometric oxidant (Scheme 9C). 64 The reaction was expanded to 1,1-disubstituted vinylphosphonates by Yao and co-workers (Scheme 9D). 65 The reaction gave the kinetically favored E isomer over the thermodynamically favored Z isomer in DMSO/DMF (consistent with Scheme 8).…”

Palladium(II)-Catalyzed Desulfitative Synthesis of Aryl Ketones from Sodium Arylsulfinates and Nitriles: Scope, Limitations, and Mechanistic Studies

“…Throughout the years, we have investigated various aryl palladium precursors such as aryl boronic acids, , aryltrifluoroborates, , and more recently benzoic acids for Pd(II)-catalyzed Heck arylations and synthesis of aryl amidines and aryl ketones . Although aryl carboxylic acids may undergo decarboxylation to form an aryl palladium complex, the use of aryl carboxylic acids for palladium-catalyzed decarboxylative coupling reactions is limited to electron-rich, sterically congested ortho -substituted substrates or the use of a Cu decarboxylative cocatalyst. ,, The limitations of Pd(II)-catalyzed decarboxylative coupling reactions prompted us to investigate alternative aryl palladium precursors.…”