Mechanistic Insights on Pd/Cu-Catalyzed Dehydrogenative Coupling of Dimethyl Phthalate

Abstract

Despite its industrial importance, very limited mechanistic information on the dehydrogenative coupling of dimethyl phthalate has been reported. Herein we report the detailed mechanism for dehydrogenative coupling of dimethyl phthalate catalyzed by [Pd­(OAc)2]/[Cu­(OAc)2]/1,10-phenanthroline·H2O (phen·H2O). The solution-phase analysis of the catalytic system by XANES shows the active species to be Pd­(II), and EXAFS supports the formation of an (acetato)­(dimethyl phthalyl)­(phen)­palladium­(II) complex from [Pd­(OAc)2]. A formation pathway of tetramethyl 3,3′,4,4′-biphenyltetracarboxylate via disproportionation of independently prepared [Pd­(OAc)­{C6H3(CO2Me)2-3,4}­(phen)] is observed with regeneration of [Pd­(OAc)2(phen)].

Bonding Energetics of Palladium Amido/Aryloxide Complexes in DMSO: Implications for Palladium‐Mediated Aniline Activation

“…[31] Other weakly coordinating oxyanions (such as OTf À ,O Ts À ,a nd TFA À )c an be readily replaced by solvent molecules. [31,32] As for palladium-amido compounds,t heir DG het (Pd À N) values (14.5-19.5 kcal mol À1 )a re shown to be remarkably larger than DG het -(PdÀO) values.T his should be primarily due to the stronger and softer basicity of ArNH À compared to oxyanions.T he thermodynamic superiority for formation of Pd À N bonds over PdÀOb onds can be used to rationalize Hartwigsobservations in competitive reactions of DG het (PdÀO) [c] 1a…”

Pd/Cu-Catalyzed Dehydrogenative Coupling of Dimethyl Phthalate: Synchrotron Radiation Sheds Light on the Cu Cycle Mechanism

“…We recently reported the mechanism of this reaction evaluated by solution-phase Xray absorption fine structure (XAFS) using Pd K-edge. 3 We also described an alternative synthesis of the intermediates as well as their catalytic and stoichiometric reactions. In this study, Pd complex 1a was easily converted in situ to [Pd(OAc) 2 (phen)] (1b), which reacted with dimethyl phthalate (3) to give [Pd(OAc){C 6 H 3 (CO 2 Me) 2 -3,4}(phen)] (1c).…”

“…3 We also described an alternative synthesis of the intermediates as well as their catalytic and stoichiometric reactions. In this study, Pd complex 1a was easily converted in situ to [Pd(OAc) 2 (phen)] (1b), which reacted with dimethyl phthalate (3) to give [Pd(OAc){C 6 H 3 (CO 2 Me) 2 -3,4}(phen)] (1c). Subsequently, disproportionation of 1c giving [Pd-{C 6 H 3 (CO 2 Me) 2 -3,4} 2 (phen)] (1d) and 1b and reductive elimination between the dimethyl phthalyl groups in 1d yielded tetramethyl 3,3′,4,4′-biphenyltetracarboxylate (4) with regeneration of 1b (Scheme 1).…”

Activator-Promoted Aryl Halide-Dependent Chemoselective Buchwald–Hartwig and Suzuki–Miyaura Type Cross-Coupling Reactions

“…The structure of the nickel complex was determined by single-crystal X-ray analysis (inset, Scheme ); this complex is converted to intermediate B in the presence of the boron-amine ate complex A . XAFS studies suggest that B is a common intermediate for both the Suzuki–Miyaura and Buchwald–Hartwig type reactions (see the Supporting Information). The oxidative homocoupling of phenylboronic acid to produce biphenyl leads to the formation of Ni(0) species C , , which is the active catalyst for the Buchwald–Hartwig type C–N bond-forming reaction.…”