Date of Award
Doctor of Philosophy
John G. Verkade
In recent years proazaphosphatranes of type P(RNCH2CH 2)3N have proven their synthetic utility as catalysts and as stoichiometric bases in a variety of organic transformations. Herein are described their application as a supporting ligand for palladium in palladium-catalyzed cross-coupling reactions, such as Buchwald-Hartwig amination, Stille, and Suzuki reactions.;Screening of various proazaphosphatranes (R = Me, Et, i-Pr, i-Bu, neo-Pent) revealed that the electron-rich, bulky, and commercially available P(i-BuNCH2CH 2)3N is the most effective ligand of this series in the aforementioned reactions. Aryl halides (bromides and iodides), including notoriously unreactive aryl chlorides, have been shown to participate in these processes.;It has also been discovered that for certain combinations of substrates in palladium-catalyzed Stille reactions, the proazaphosphatranes P(PhCH 2NCH2CH2)3N and P(PhCH2NCH 2CH2)2N(i-BuNCH2CH 2) provided even more active palladium catalysts than P(i-BuNCH 2CH2)3N.;Additionally, the synthesis of the new bicyclic triaminophosphine ligand P(i-BuNCH2)3CMe and its efficacy in Buchwald-Hartwig amination reactions is demonstrated. This ligand provides a remarkably general, efficient, and mild palladium catalyst for aryl iodide amination. This ligand also allows a weak base, such as Cs2CO 3, to function in these reactions.;Finally, the first general protocol for the ligand-, copper-, and amine-free Sonogashira reaction has been developed. The success of this method hinges on the use of tetrabutylammonium acetate as the base.
Digital Repository @ Iowa State University, http://lib.dr.iastate.edu/
Urgaonkar, Sameer, "Proazaphosphatranes: a highly effective class of triaminophosphine ligands in palladium-catalyzed cross-coupling reactions " (2004). Retrospective Theses and Dissertations. 1707.