Discovery and development of transition metal catalysts for carbon-carbon and carbon-heteroatom bond formations [electronic resource] : Isolation and reactivity of catalytic intermediates.

9780496570102

2003

1 online resource (286 p.)

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A high-throughput screening assay for the discovery of catalysts for transition metal-catalyzed cross-coupling reactions was developed. The assay was based on fluorescence resonance energy transfer (FRET) that occurred between a fluorophore and a quencher molecule. To screen catalysts for the Heck reaction, a base and catalyst were added to a solution of a dansyl flurophore that contained an olefin and a diazo quencher molecule that contained an aryl bromide. The decrease of fluorescence emission, as detected by a fluorescence spectrometer that is capable of analyzing a 96-well plate reader, allowed for the rapid determination of catalyst activity. From these results, the first room-temperature Heck reaction of aryl bromides was discovered. A mechanistic investigation of the active catalyst in this room-temperature Heck reaction led to the discovery of a palladium(I) dimeric complex that catalyzed the coupling of an aryl chloride and amine or an aryl bromide and boronic acid in less than 15 min at room temperature. This mechanistic investigation also led to the discovery of three-coordinate arylpalladium(II) halide complexes containing one dative ligand that are stabilized by weak agostic interactions. A series of these complexes of the general formula, LPd(Ar)(X), were prepared with L = 1-AdPtBu 2, PtBu3, or FcP tBu2(Ph)5 and X = Br, Cl, I, or OTf. Starting from these monomeric complexes, three-coordinate complexes that appear on the proposed catalytic cycles for the palladium-catalyzed etherification and amination of aryl halides were synthesized. The reactivity of these complexes provided evidence of their intermediacy in palladium-catalyzed cross-coupling reactions. In addition, the first reductive elimination of ether from an isolated, monomeric palladium alkoxide complex was observed.

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English

July 12, 2011

Thesis (Ph.D.)--Yale University, 2003.

Yale University.