No description available.

No description available.

No description available.

Two new general synthetic routes to phosphines were developed. The first method described directly converts phosphonates to phosphine oxides using organometallic nucleophiles. This reaction proceeds through a five-coordinate phosphorus intermediate. The second synthetic method uses a deprotonated secondary phosphine oxide for nucleophilic addition to an alkyl halide to form a tertiary phosphine oxide. This reaction proceeds through a standard SN2 mechanism, however in extreme cases a competitive electron transfer reaction was observed. These syntheses were used to make a new dimethyl phosphine (MeJPhos). This phosphine was used as a ligand for metal complexes and compared against a series of structurally related (JohnPhos) phosphines. MeJPhos was found to be the strongest electron donor in the series MeJPhos, EtJPhos, iPrJPhos, CyJPhos, and tBuJPhos. These ligands were then used to study structural effects of ligands on Buchwald-Hartwig cross-coupling catalysis. It was found that only tBuJPhos performed catalytically. This observation is likely due to the smaller steric profile of the other JohnPhos ligands. Specifically, it is the inability to perform the reductive elimination step of the catalytic cycle that prevents turnover. Ozonolysis was used to oxidize alkenes to aldehydes directly. Typically with ozonolysis, a secondary ozonide is formed as the product that must be chemically reacted in a subsequent step. By trapping out the immediate chemical precursor to the secondary ozonide with water, the formation of secondary ozonides was avoided. This method produced aldehydes directly from aryl alkenes in good to excellent yields. This dissertation includes previously published and unpublished co-authored material.

Thesis. 1977. Ph.D.--Massachusetts Institute of Technology. Dept. of Chemistry. / M̲i̲c̲ṟo̲f̲i̲c̲ẖe̲ c̲o̲p̲y̲ a̲v̲a̲i̲ḻa̲ḇḻe̲ i̲ṉ A̲ṟc̲ẖi̲v̲e̲s̲ a̲ṉḏ S̲c̲i̲e̲ṉc̲e̲. / Vita. / Includes bibliographical references. / Ph.D.

Thesis (Ph.D.)--McMaster University, 2005. / Supervisor: John F. Valliant. Includes bibliographical references.

none

Thèse doctorat : Chimie et Physico-Chimie Moléculaires : Nancy 1 : 2006. / Titre provenant de l'écran-titre.

Includes bibliographical references (p. 176-187).

The goal of this research was to synthesize and study new phosphine crown ethers. The first target molecule was 5-phenylphoshinobis(2-hydroxy,1,3-xylyl-18-crown-5). We tried to synthesize this target molecule in six steps. 5-Bromophenol was reacted with formaldehyde, dimethylsulfate, phosphorus tribromide and tetraethylene glycol in the presence of sodium hydride producing the main intermediate molecule, 5-bromo-2-methoxy-1,3-xylyl-l8-crown-5. This molecule was reacted with n-butyllithium and dimethyl phenylphosphinite at the low temperature . NMR evidence indicated that was not obtained.The second target molecule, the oxide of 5-phenylphosphinobis(2-hydroxy-1,3-xylylcrown-5) was synthesized in nine steps. The main intermediate, 5-bromo-2-methoxy-1,3-xylyl-18-crown-5 was reacted with n-butyllithium and dimethyl phenylphosphinite to form the phosphine. This phosphine was oxidized with hydrogen peroxide. The OCH3 bond of this crown ether was cleaved by using LiI in boiling anhydrous pyridine. NMR data indicated the product was formed. / Department of Chemistry