Palladacycle catalysis: an innovation to the Suzuki–Miyaura cross-coupling reaction

Abstract

Herein we report a Suzuki-Miyaura type cross-coupling between an aryl halide and a functionalized boronic acid palladacycle in the absence of an external catalyst. This reaction is an unprecedented case of catalysis in palladium metallacycle chemistry.

From Chemical Serendipity to Translational Chemistry: New Findings in the Reactivity of Palladacycles

“…We initiated our research by searching for novel cyclopalladated compounds supported by Suzuki couplings, for which we chose the treatment of palladacycles bearing ab oronic acidf unctionality with aryl halides, for which thiosemicarbazone palladacycles were selected, because the latter palladacycles themselves are rather insoluble in the more usual organic solvents as well as in water.W ew erea ble to make complex 22 either directly from the tetranuclear cluster or via triphenylphosphine derivative 21,i nb oth cases under catalytic conditions (Scheme 5). [25] We also observed,h owever, that 22 could be prepared directly from 21 in the absence of catalyst, which was clearlya novelty to the Suzuki-Miyaura cross-coupling reaction. This was made possible by close inspection of the thin layer chromatography plates, which allowed us to tentatively propose a plausible Pd II /Pd IV[26] mechanism, which could be in agreement with our discovery (Scheme 6).…”

“…We initiated our research by searching for novel cyclopalladated compounds supported by Suzuki couplings, for which we chose the treatment of palladacycles bearing a boronic acid functionality with aryl halides, for which thiosemicarbazone palladacycles were selected, because the latter palladacycles themselves are rather insoluble in the more usual organic solvents as well as in water. We were able to make complex 22 either directly from the tetranuclear cluster or via triphenylphosphine derivative 21 , in both cases under catalytic conditions (Scheme ) …”

“…The DFT optimized( orange) and crystal (blue) structures are compared on the right.R eproduced from Ref. [25].C opyright 2016 The Royal SocietyofC hemistry.…”

“…Reproduced from Ref. [25].Copyright 2016 The Royal Society of Chemistry. ChemistryOpen 2018, 7,754 -763 www.chemistryopen.org 2018 The Authors.…”

Synthesis and catalytic study in the Suzuki-Miyaura reaction of a family of palladium compounds

“…Given our vast experience in the synthesis and characterisation of cyclopalladated compounds [5] and their use as catalysts in the Suzuki-Miyaura reaction [6,7], we reasoned that by using the thiosemicarbazone as bidentate instead of tridentate, the greater accessibility of palladium would give a better catalytic activity. For this reason the synthesis of ligands 1-3 (scheme1) was carried out.…”