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Timothy E Barder

Publications and source records attributed to Timothy E Barder.

7 recordsLinked to original sources
PubMed2007

Benchtop monitoring of reaction progress via visual recognition with a handheld UV lamp: in situ monitoring of boronic acids in the Suzuki-Miyaura reaction.

[reaction: see text] Although boronic acids are widely used in metal-catalyzed reactions, it is difficult to assay their consumption. As such, we developed a reversible fluorescent sensor that is activated upon binding a boronic acid. The sensor can be used to monitor consumption of a boronic acid in Suzuki-Miyaura reactions. Importantly, only a standard handheld long-wave UV lamp (365 nm) is required and fluorescence is easily detectable with the naked eye without disturbing the reaction mixture.

Boronic Acids↗
PubMed2006

Synthesis, structural, and electron topographical analyses of a dialkylbiaryl phosphine/arene-ligated palladium(I) dimer: enhanced reactivity in Suzuki-Miyaura coupling reactions.

The treatment of bis(2-(dicyclohexylphosphino)-2',6'-dimethoxybiphenyl)PdCl2 with AgBF4 produces an air-stable phosphine/arene-ligated Pd(I) dimer with two seemingly identical Pd-arene interactions by X-ray crystallography. However, NMR and theoretical electron topographical analyses of this complex distinguish between these two interactions. One interaction is classified as an arenium-like complex, while the other is classified as a pi-interaction. Additionally, this complex is a suitable precatalyst for high yielding Suzuki-Miyaura coupling reactions in short reaction times.

Biphenyl Compounds↗
PubMed2005

Catalysts for Suzuki-Miyaura coupling processes: scope and studies of the effect of ligand structure.

Suzuki-Miyaura coupling reactions of aryl and heteroaryl halides with aryl-, heteroaryl- and vinylboronic acids proceed in very good to excellent yield with the use of 2-(2',6'-dimethoxybiphenyl)dicyclohexylphosphine, SPhos (1). This ligand confers unprecedented activity for these processes, allowing reactions to be performed at low catalyst levels, to prepare extremely hindered biaryls and to be carried out, in general, for reactions of aryl chlorides at room temperature. Additionally, structural studies of various 1.Pd complexes are presented along with computational data that help elucidate the efficacy that 1 imparts on Suzuki-Miyaura coupling processes. Moreover, a comparison of the reactions with 1 and with 2-(2',4',6'-triisopropylbiphenyl)diphenylphosphine (2) is presented that is informative in determining the relative importance of ligand bulk and electron-donating ability in the high activity of catalysts derived from ligands of this type. Further, when the aryl bromide becomes too hindered, an interesting C-H bond functionalization-cross-coupling sequence intervenes to provide product in high yield.

Boronic Acids↗
PubMed2004

Copper-diamine-catalyzed N-arylation of pyrroles, pyrazoles, indazoles, imidazoles, and triazoles.

This paper details the copper-catalyzed N-arylation of pi-excessive nitrogen heterocycles. The coupling of either aryl iodides or aryl bromides with common nitrogen heterocycles (pyrroles, pyrazoles, indazoles, imidazoles, and triazoles) was successfully performed in good yield with catalysts derived from diamine ligands and CuI. General conditions were found that tolerate functional groups such as aldehydes, ketones, alcohols, primary amines, and nitriles on the aryl halide or heterocycle. Hindered aryl halides or heterocycles were also found to be suitable substrates using the conditions reported herein.

Catalysis↗
PubMed2004

Efficient catalyst for the Suzuki-Miyaura coupling of potassium aryl trifluoroborates with aryl chlorides.

Palladium-catalyzed Suzuki-Miyaura cross-coupling reactions of aryl- and heteroaryl chlorides with potassium aryl- and heteroaryltrifluoroborates have been accomplished with the supporting ligand S-Phos in good to excellent yield. Hindered biaryls and substrates containing a variety of functional groups can be prepared. Suzuki-Miyaura couplings of a 3-pyridyl boron-based nucleophile with aryl- and heteroaryl chlorides proceed in good to very good yield. [reaction: see text]

Borates↗