Bimetallic Cu/Pd Catalysts with Bridging Aminopyrimidinyl Phosphines for Decarboxylative Cross‐Coupling Reactions at Moderate Temperature

Abstract

A bimetallic catalyst system is presented that enables the decarboxylative cross‐coupling of triflates with carboxylate salts at only 100 °C, which is 70 °C lower than with previous Cu/Pd‐based systems. The new protocol allows the coupling of a broad range of aryl triflates with various substituted 2‐nitrobenzoates in good to excellent yields. The key feature of the catalyst system is a bidentate P,N‐ligand designed to bridge the Pd and Cu centres and thereby facilitating the rate‐determining transmetalation step. Mass spectrometry (ESI‐MS) studies support the ability of the aminopyrimidinyl phosphine to simultaneously coordinate copper and palladium.

Combined Experimental and Computational Mechanistic Investigation of the Palladium-Catalyzed Decarboxylative Cross-Coupling of Sodium Benzoates with Chloroarenes

“…The mechanisms of metal-catalyzed protodecarboxylation and decarboxylative cross-coupling reactions have been studied. ,, In contrast to systems that use Ag ,− or Cu ,− additives, systems utilizing only a Pd catalyst are much less well understood. Unlike decarboxylative Heck reactions or protodecarboxylation reactions, there is minimal experimental mechanistic data on palladium-catalyzed decarboxylative cross-coupling without copper or silver. − A variety of palladium-catalyzed methods have been developed including work by Bilodeau and Forgione on coupling heteroarylcarboxylic acids, , a report by Eli Lilly to synthesize a desired scaffold, , and advancement of intramolecular cyclizations by Shen, , in addition to others. , However, these reactions have not been thoroughly investigated.…”

Mechanism of Cu/Pd-Catalyzed Decarboxylative Cross-Couplings: A DFT Investigation

“…For the mechanistically more complex decarboxylative couplings mediated by bimetallic catalyst systems, a similarly detailed computational study would be of substantial value. With state-of-the-art catalysts, the protodecarboxylation of o -nitrobenzoic acids with a copper/phenanthroline system can meanwhile be performed at 100 °C, while decarboxylative cross-couplings with aryl triflates, in which copper/phenanthroline systems are employed as the decarboxylation cocatalysts, still do not proceed below 150 °C. , Thus, the decarboxylation is not necessarily rate-determining, and it is no longer sufficient to single out the decarboxylation step in computational studies to obtain a lead for further catalyst optimization. Instead, computational modeling should cover the entire catalytic cycle.…”

Advancing Inorganic Coordination Chemistry by Spectroscopy of Isolated Molecules: Methods and Applications

“…Then it becomes possible not only to study the kinetics of solution reactions by using ESI-MS to probe reactant and product concentrations [11] but also to study the mechanism by resolving charged intermediates, for example in selected homogeneously catalysed reactions. [12][13][14][15][16] ESI-IMS-MS and ESI-MS-IMS-MS: Ion mobility mass spectrometry (IMS-MS) as applied to the structural characterization of molecular ions dates back to the early 1990's. [17] In its first and conceptually simplest "drift-tube" variant, a DC electric field pulls ions through a collision cell containing an inert collision gas such as helium or nitrogen (at a pressure of a few mbar).…”

“…Then it becomes possible not only to study the kinetics of solution reactions by using ESI‐MS to probe reactant and product concentrations [11] but also to study the mechanism by resolving charged intermediates, for example in selected homogeneously catalysed reactions. [ 12 , 13 , 14 , 15 , 16 ]…”