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Mechanistic studies on iridium catalyzed allylic substitution

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Title: Mechanistic studies on iridium catalyzed allylic substitution
Author(s): Madrahimov, Sherzod
Director of Research: Hartwig, John
Doctoral Committee Chair(s): Hartwig, John
Doctoral Committee Member(s): Girolami, Gregory; Rauchfuss, Thomas; Burke, Martin
Department / Program: Chemistry
Discipline: Chemistry
Degree Granting Institution: University of Illinois at Urbana-Champaign
Degree: Ph.D.
Genre: Dissertation
Subject(s): allylic substitution mechanistic studies iridium catalyzed
Abstract: Mechanistic studies on iridium catalyzed allylic substitution reactions catalyzed by iridium phosphoramidite complexes revealed that the active catalyst is generated through a base assisted cyclometalation of the phosphoramidite to form five-membered iridacycle. A mechanism for the reaction was proposed based on a series of kinetic experiments. According to this mechanism the product bound cyclometalated complex is the resting state of the catalyst. First examples of allyliridium complexes containing cyclometalated phosphoramidite ligand were prepared. A series of stoichiometric experiments showed that these allyliridium complexes were chemically and kinetically competent to be intermediates in iridium catalyzed allylic substitution reactions. Double inversion mechanism for the iridium catalyzed allylic substitution reaction was also shown through a combination of catalytic and stoichiometric reactions of cyclometalated iridium complexes. A series of kinetic studies also showed that oxidative addition was the enantiodetermining step in iridium catalyzed allylic substitution. Finally, allyliridium complexes containing cyclometalated triphenylphosphite ligand were prepared. These complexes were competent to be intermediates in non-stereoselective allylic substitution reactions catalyzed by iridium triphenylphosphite complexes. A series of kinetic experiments showed that regioselectivity of iridium catalyzed allylic substitution is likely controlled by a larger binding affinity of terminal alkenes to iridium center over internal disubstituted alkenes.
Issue Date: 2012-09-18
URI: http://hdl.handle.net/2142/34371
Rights Information: Copyright 2012 Sherzod Madrahimov
Date Available in IDEALS: 2012-09-18
Date Deposited: 2012-08
 

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