Palladium(0)-Catalyzed Intramolecular Decarboxylative Allylation of Ortho Nitrobenzoic Esters

Abstract

A Pd/Ag bimetallic system has been developed for the decarboxylative allylation of ortho-nitrobenzoic esters in an intramolecular fashion. In contrast to the typical sp(2)-sp(3) cross-coupling approach which requires air and moisture sensitive preformed organometallic reagents, we provide an alternative route to the synthesis of ortho-allyl nitroarenes from the corresponding ortho-nitrobenzoic acid derivatives. The reaction proceeds through a mechanistically distinct decarboxylative metalation pathway. A cooperative reactivity of palladium and silver is crucial for the reaction outcome.

CuI/AgI‐Promoted Decarboxylative Alkynylation of ortho‐Nitro Benzoic Acids

“…This indicates that electron withdrawing substituents may facilitate the decarboxylation but they decrease the ability of the aryl anion to serve as a σ‐donor for the copper(II)‐acetylide. The same observation was also found in our previous work of decarboxylative allylation of ortho nitrobenzoic esters . Selective reduction of nitro group followed by cyclization leads to the formation of 2‐phenylindole from 3 a (see the Supporting Information).…”

The Evolution of Decarboxylative Allylation: Overcoming pKa Limitations

“…This suggests that resonance donation from the heterocyclic oxygen might promote electrophilic palladation and subsequent decarboxylation (Scheme , B ). While this hypothesis most easily explains our data, others have observed decarboxylative allylation of nitroaromatics, fluoroarenes, and dienes where this electrophilic palladation/decarboxylation mechanism would be expected to be less accessible.…”

Aryl-Decarboxylation Reactions Catalyzed by Palladium: Scope and Mechanism

“…Precatalyst Pd5 (Scheme 21) was preferred for this reaction, possibly because the silane and COD ligands are fully organic soluble and minimally coordinating after precatalyst activation. Other palladium-catalyzed decarboxylative allylations have been reported with the addition of silver 124 or copper and silver. 125 Su and co-workers reported a decarboxylative Sonogashira reaction between electron-rich benzoic acids and alkynes (Scheme 24).…”