Additive-Free Palladium-Catalyzed Decarboxylative Cross-Coupling of Aryl Chlorides

Abstract

The cross-coupling of sodium (hetero)aryl carboxylates with (hetero)aryl chlorides proceeds with 1 mol % palladium catalyst and does not require inorganic base, silver salts, or copper salts. This coupling uses two low energy partners, and the only stoichiometric byproducts are carbon dioxide and sodium chloride. The substrate scope includes less activated aryl chlorides and carboxylates (>25 examples). The palladium loading could be reduced to 0.1 mol %, and Buchwald-style precatalysts could be used.

Gold Catalyzed Decarboxylative Cross-Coupling of Iodoarenes

“…Less activated substrates required elevated temperatures and/or increased catalyst loading ( 3v – 3y ). It is particularly exciting that products 3x and 3y could be isolated in any yield given the scope limitations of other decarboxylative cross-coupling reactions. ,, Substrates with an ortho C–H bond did not afford product with palladium catalyzed reactions, ,, which again disfavors a mechanism based on trace metal contamination. Additionally, a single ortho -fluorine ( 3x ) or chlorine ( 3y ) substituent is only mildly polarizing and was sufficient for decarboxylation.…”

“…Our lab has focused on decarboxylative cross-coupling. 42,43 Decarboxylative functionalization reactions are recognized as promising alternatives to traditional cross-couplings because expensive or unstable organometallic reagents can be replaced by readily available benzoic acids . [44][45][46][47][48] Inspired by two reports describing stoichiometric gold(I) mediated decarboxylation, 49,50 we surmised that this elementary step could offer an alternate pathway to gold-aryl complexes, obviating traditional transmetalation.…”

“…It is particularly exciting that substrates 3x and 3y can be (%) isolated in any yield given the scope limitations of other decarboxylative cross-coupling reactions. 43,48,56 Substrates with an ortho C-H bond did not afford product with palladium catalyzed reactions 42,43,56 and a chlorine substituent (3y) is not considered to be particularly polarizing. A substrate with an orthomethoxy was not activated enough to provide an acceptable yield (3z, Fortho = 0.29).…”

“…Our lab has focused on developing decarboxylative cross-coupling reactions. , Decarboxylative functionalization reactions are recognized as promising alternatives to traditional cross-couplings because expensive or unstable organometallic reagents can be replaced by readily available benzoic acids. − Inspired by two reports describing stoichiometric gold­(I) mediated decarboxylation, , we surmised that this elementary step could offer an alternate pathway to gold-aryl complexes. ,, Alternatively, a dual catalytic cycle using a second metal, also capable of decarboxylation, could enable access to less frequently used transmetalation partners. Presented herein is a gold catalyzed decarboxylative cross-coupling reaction between iodoarenes and (hetero)­aryl carboxylates (Scheme e).…”

Aryl-Decarboxylation Reactions Catalyzed by Palladium: Scope and Mechanism

“…A 2019 contribution by Topczewski and co-workers illustrated that both electron-deficient and electron-rich (hetero)arenecarboxylic acids can participate in decarboxylative cross-coupling (Scheme 20). 101 The substrate scope of this process was quite broad with respect to the aryl chloride. The reaction could forge biaryl bonds between two heterocycles and the products included systems which could be used for organic materials.…”