Cynthia M. Dupureur, Interim Department Chair
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Chemistry & Biochemistry: Summer 2016
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Dr. Bauer received his Diploma (M.Sc.thesis degree) and his Ph.D from the University of Erlangen-Nuremberg. He held a postdoctoral position at the University of California, Riverside and a position as Visiting Assistant Professor prior to joining the UM-St. Louis faculty in Fall 2006.
Dr. Bauer’s research interests are in the area of Organic and Organometallic Chemistry. Organometallic chemistry is the study of compounds having metal-carbon bonds. Organometallic compounds often have unique geometries and exhibit reactivities as a result of the electronic properties of the metal. Organometallic compounds are important in catalysis, medicine, and the construction of molecular scale devices (nanoscience).
Phopshoramidite and phosphinooxazoline ligands have recently attracted considerable interest as ligands for a variety of transition metal catalyzed organic transformations. These ligands are easy to synthesize and can be sterically and electronically modified at several positions in their molecular framework.
Dr. Bauer designed and synthesized several novel, electronically and sterically fine-tuned phosphoramidite and phosphinooxazoline ligands. As a new class of ligands, thio derivatives of phosphoramidites were synthesized. These ligands were subsequently converted to a variety of ruthenium, rhodium, iridium and iron complexes. The impact of the ligand structure on the physical and chemical properties of its respective metal complexes was investigated.
The Bauer group has shown that phosphoramidite containing half sandwich complexes of ruthenium are catalytically active in the formation of b-oxo esters from propargylic alcohols and carboxylic acids (see graphics). The ligand structure has a profound impact on the catalytic activity of the corresponding metal complex. Structurally related chiral at metal ruthenium complexes have exhibited catalytic activity in the Mukaiyama aldol reaction.
Iron is a cheap and non-toxic alternative to well-established, catalytically active transition metals. The Bauer group has demonstrated for the first time that phosphinooxazoline complexes of iron are catalytically active in the oxidation of benzylic methylene groups to ketones utilizing t-BuOOH as the oxidant.
Allenylidene complexes are cumulene-type compounds, which are readily accessible from propargylic alcohols and appropriate precursor metal complexes. The allenylidene complexes are of interest as possible intermediate in catalytic propargylic substitution reactions. Dr. Bauer has also demonstrated a route to chiral at metal allenylidene complexes, which were obtained from corresponding precursors with chirality transfer. Catalytic investigations are currently underway.
″Synthesis,Characterization and Catalytic Activity of Indenyl Tris(N-pyrrolyl-phosphine Complexes of Ruthenium,″ M. J. Stark, M. J. Shaw, N. P. Rath and E. B. Bauer, Eur. J. Inorg. Chem. 2016, 1093.102.
″Ferrocenium Hexafluorophosphate as an inexpensive mild catalyst for the etherification of Propargylic alcohols,″ M. J. Queensen, J. M. Rabus and E. B. Bauer, J. Mol. Catal. A, 2015, 407, 221.
″Iron Catalysis: Historic Overview and Current Trends, ″ E. B. Bauer, Topics in Organometallic Chemistry, 2015, 50, 1
″Topics in Organometallic Chemistry, Vol 50, Iron Catalysis II,″ E. B. Bauer, Ed.; Springer, NY, 2015, 262 pp.
"Diastereoselective Attack on Chiral-at-Metal Ruthenium Allenylidene Complexes to Give Alkynyl Complexes" M. Queensen, N. P. Rath, and E. B. Bauer, Organometallics, 2014, 33, 5052.
″New bis(imino)pyridine complexes of iron(II) and iron(III), and their catalytic-activity in the Mukaiyama aldol reaction″, P. Shejwalkar, N. P. Rath and E. B. Bauer, Synthesis, 2014, 46, 57
"Ruthenium complexes of the general formula [RuCl2(PHOX) 2] and their catalytic activity in the Mukaiyama aldol reaction," N. Curvey, A. K. Widaman, N. P. Rath and E. B. Bauer, Tetrahedron Lett. 2014, 55, 3033.
"Etherification reactions of propargylic alcohols catalyzed by a cationic ruthenium allenylidene complex," D. F. Alkhaleeli, K. J. Baum, J. M Rabus and E. B. Bauer, Catalysis Comm. 2014, 47, 45.
"Polydentate pyridyl ligands and the catalytic activity of their iron(II) complexes in oxidation reactions utilizing peroxides as the oxidants," M. Lenze, S. Sedinkin and E. B. Bauer, J. Mol. Catal. A: Chem. 2013, 373, 161
"Iron(III) a-Aminopyridine Complexes and their Catalytic Activity in Oxidation Reactions: A comparative Study of Activity and Ligand Decomposition," M. Lenze, E. T. Martin, N. P. Rath and E. B. Bauer, ChemPlusChem 2013, 78, 101.
"Transition-metal-catalyzed functionalization of propargylic alcohols and their derivatives," E. B. Bauer, Synthesis 2012, 44, 1131.
Chiral-at-metal complexes and their catalytic applications in organic synthesis," E. B. Bauer, Chem. Soc. Rev. 2012, 41, 3153.
"New five-coordinate Ru(II) phosphoramidite complexes and their catalytic activity in propargylic amination reactions", A. K. Widaman, N. P. Rath and E. B. Bauer, New J. Chem. 2011, 35, 2427
"New iron(II) a-iminopyridine complexes and their catalytic activity in the oxidation of activated methylene groups and secondary alcohols to ketones", P. Shejwalkar, N. P. Rath and E. B. Bauer, Dalton Trans. 2011, 7617.
"Synthesis and Structural Characterization of a Series of New Chiral-at-Metal Ruthenium Allenylidene Complexes", S. Costin, A. K. Widaman, N. P. Rath and E. B. Bauer, Eur. J. Inorg. Chem. 2011, 8, 1269.