In Situ Kinetic Studies on Rhodium (II) Carboxylate Catalysts with Cyclopropanation Reactions Pubblico

Abstract

A systematic kinetics study was done via ReactIR (TM) on dirhodium catalysts with the cyclopropanation reaction to further understand the catalytic cycle, as well as the effect of the catalysts’ ligands on the performance of the catalyst. Using the RPKA study, the rhodium (II) triarylcyclopropane carboxylate catalyst was found to be robust, as the catalytic activity is maintained during the course of the reaction. The rhodium (II) catalysts with different ligands exhibit different reactivities, some catalyzing the reaction faster than others; however, all of the catalysts tested were able to achieve at least 40,000 turnover numbers (TON). This study gives a better understanding of the factors that affect catalyst activity and stability under high TON conditions, and results from this study can help with the design of ligands that will lead to more efficient and practical rhodium (II) catalysts. It was also found that dimethylcarbonate (DMC) can be used as a greener alternative for solvent compared to dichloromethane (DCM), and not only does it give higher enantioselectivity, it allows for the use of lower catalyst loadings at higher temperatures. 

Table of Contents

1) Introduction ................................................................................................................................1

1.1) Rhodium (II) Catalysts and Background ...................................................................................1

1.2) Cyclopropanation Reaction and Carbenes ..............................................................................2

1.3) High Turnover Numbers with Rhodium (II) Catalysts .............................................................4

1.4) Reaction Progress Kinetic Analysis (RPKA) ..............................................................................4

2) Results and Discussion .................................................................................................................5

2.1) Initial Studies with Triarylcyclopropane Carboxylate Catalysts ..............................................5

2.2) Molecular Sieves as Drying Agent .........................................................................................10

2.3) A Greener, Safer Solvent ......................................................................................................17

2.4) Discussion ...............................................................................................................................27

3) Conclusions ................................................................................................................................29

4) Experimental ..............................................................................................................................30

4.1) General Remarks .....................................................................................................................30

4.2) General Procedure for Synthesis of Diazo Compounds ..........................................................30

4.3) General Procedure of ReactIR (TM) Set-up and Cyclopropanation Reactions ...........................31

4.4) General Procedure for ReactIR (TM) Data Analysis .....................................................................33

4.5) Analysis of Cyclopropane Products .........................................................................................34

4.6) HPLC Traces ............................................................................................................................35

References .....................................................................................................................................47 

About this Honors Thesis

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School	Emory College
Department	Chemistry
Degree	B.S.
Submission	Honors Thesis
Language	English
Research Field	Chemistry, Organic
Parola chiave	dirhodium catalyst cyclopropanation reaction
Committee Chair / Thesis Advisor	Davies, Huw, Emory University
Committee Members	Jui, Nathan, Emory University Bhasin, Paul, Emory University

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