426823-26-9Relevant articles and documents
[2,2′-bipyridin]-6(1 H)-one, a Truly Cooperating Ligand in the Palladium-Mediated C-H Activation Step: Experimental Evidence in the Direct C-3 Arylation of Pyridine
Salamanca, Vanesa,Toledo, Alberto,Albéniz, Ana C.
supporting information, p. 17851 - 17856 (2019/01/04)
The ligand [2,2′-bipyridin]-6(1H)-one (bipy-6-OH) has a strong accelerating effect on the Pd-catalyzed direct arylation of pyridine or arenes. The isolation of relevant intermediates and the study of their decomposition unequivocally show that the deprotonated coordinated ligand acts as a base and assists the cleavage of the C-H bond. Mechanistic work indicates that the direct arylation of pyridine with this ligand occurs through a Pd(0)/Pd(II) cycle. Because of this dual ligand-intramolecular base role, there is no need for an available coordination site on the metal for an external base, a difficulty encountered when chelating ligands are used in coupling reactions that involve a C-H cleavage step.
Ligand-promoted C3-selective arylation of pyridines with Pd catalysts: Gram-scale synthesis of (±)-preclamol
Ye, Mengchun,Gao, Guo-Lin,Edmunds, Andrew J. F.,Worthington,Morris, James A.,Yu, Jin-Quan
supporting information; experimental part, p. 19090 - 19093 (2012/01/07)
The first example of Pd-catalyzed, C3-selective arylation of unprotected pyridines has been developed by employing a catalytic system consisting of Pd(OAc)2 and 1,10-phenanthroline. This protocol provides an expeditious route to an important class of 3-arylpyridines and 3-arylpiperidines frequently found in bioactive compounds. A brief synthesis of the drug molecule (±)-preclamol is also reported.
9-Fluorenylphosphines for the Pd-catalyzed Sonogashira, Suzuki, and Buchwald-Hartwig coupling reactions in organic solvents and water
Fleckenstein, Christoph A.,Plenio, Herbert
, p. 2701 - 2716 (2008/03/14)
The lithiation/alkylation of fluorene leads to various 9-alkyl-fluorenes (alkyl = Me. Et, /Pr, -Pr. -C18H25) in > 95% yields, for which lithiation and reaction with R2PCl (R = Cy, iPr, tBu) generates 9-alkyl, 9-PR2fluorenes which constitute electron-rich and bulky phosphine ligands. The in-situ-formed palladium-phosphinc complexes ([Na2PdCl4], phosphonium salt, base, substrates) were tested in the Sonogashira. Suzuki, and Buchwald-Hartwig reactions of aryl chlorides and aryl bromides in organic solvents. The Sonogashira coupling of aryl chlorides at 100-120°C leads to >90% yields with 1 mol % of Pd catalyst. The Suzuki coupling of aryl chlorides typically requires 0.05 mol % of Pd catalyst at 100°C in dioxane for quantitative product formation. To carry out "green" cross-coupling reactions in water, 9-ethylfluorenyldicyclohexylphosphine was reacted in sulphuric acid to generate the respective 2-sulfonated phosphonium salt. The Suzuki coupling of activated aryl chlorides by using this water-soluble catalyst requires only 0.01 mol% of Pd catalyst, while a wide range of aryl chlorides can be quantitatively converted into the respective coupling products by using 0.1-0.5 mol % of catalyst in pure water at 100°C. Difficult substrate combinations, such as naphthylboronic acid or 3-pyridylboronic acid and aryl chlorides are coupled at 100°C by using 0.1-0.5 mol % of catalyst in pure water to obtain the respective N-heterocycles in quantitative yields. The copper-free aqueous Sonogashira coupling of aryl bromides generates the respective tolane derivatives in > 95 % yield.
