University of Missouri - Saint Louis

The Graduate School

Announcement

An oral examination in defense of the dissertation for the degree

Doctor of Philosophy in Chemistry

Pushkar S. Shejwalkar
M.S. in Chemistry, December 2010, University of Missouri-Saint Louis
M.Sc. in Organic Chemistry, December 2005, Ramnarain Ruia College, Mumbai University.


Application of Iron Complexes as Catalysts in C-O and C-C bond forming reactions

 

Abstract

‘Green Chemistry’ is a philosophy that encourages chemists in research and industry to reduce toxic waste for cleaner and safer chemical production. Oxidation reactions are commonly used in industry and are traditionally achieved by methods that involve toxic metals (such as chromium) and solvents, generating considerable waste compared to the value of the final product. The Mukaiyama Aldol reaction is another organic reaction that utilizes metals as Lewis acid catalysts. The principles of Green Chemistry suggest that chemical reactions should be performed with a maximum of efficiency and with a minimum of side product formation, accompanied by a minimal use of the toxic reagents. The overall purpose of the PhD project was to replace toxic metals in catalyst systems by environmentally more benign iron. The research focused on synthesizing iron based organometallic complexes, that were fully characterized and then employed as catalysts, as compared to conventional in situ synthesis of catalytically active complexes (where the identification and modification of active sites is difficult due to lack of knowledge of the exact structure of the metal complex). Iron complexes of the general formula [FeBrCp(CO)(L)] (1) where L is a monodentate phosphoramidite, [Fe(OTf)2(L)2] (2) where L is bidentate -iminopyridine and OTf is triflate, and [Fe2Cl6(L)] (3) where L is a tris-dentate -diiminopyridine were synthesized and characterized by various instrumental methods such as multinuclear NMR, IR, Mass-spectrometry, UV-VIS spectroscopy, elemental analyses, and single crystal X-ray diffraction methods. Complexes 1 and 2 were successfully employed as catalyst precursor in oxidation reactions of activated methylene groups and secondary alcohols to obtain the corresponding ketones in 21-91% yield. Complex 3 was successfully employed as catalysts after activation using AgSbF6 in Mukaiyama Aldol reactions to give silyl protected -hydroxyketones in 43-91% yield.


 

Date: July 12, 2013

Time: 10:00am to 12:00 noon

Place: 451, Benton Hall

 

Defense of Dissertation Committee

 

Prof. Dr. Eike B. Bauer, Ph.D. (Advisor)

Prof. Dr. Janet Braddock-Wilking, Ph.D.

 

Prof. Dr. Alexei V. Demchenko, Ph.D.

Prof. Dr. Keith J. Stine, Ph.D.