An Investigation on the Diastereoselectivity of α-Methylstyrene Cyclopropanations Catalyzed by Dirhodium (II) Catalysts Open Access

Abstract

Dirhodium (II) based catalysis have proven to be important tools for chemical syntheses, allowing for the development of bonds that would otherwise be difficult to obtain. In particular, rhodium-catalyzed cyclopropanations provide an efficient way to produce three-membered rings – scaffolds of interest in the context of pharmaceutics and natural synthesis. Though the Davies group has developed rhodium catalysts that allow these reactions to be performed efficiently and with high levels of selectivity, there are still gaps to be filled in these studies. This current study explores the diastereoselectivity of cyclopropanations between α-methylstyrene and 2,2,2-trichloroethyl 2-(4-bromophenyl)-2-diazo acetate in the presence of 11 different dirhodium (II) catalysts. The obtained results represent an initial step in the further refining of cyclopropanation-directed dirhodium (II) catalysts.

Table of Contents

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

1.a) Rhodium (II) Catalysis…….………………………………………………………………….1

1.b) Cyclopropanation Reactions………………………………………………………………….2

1.c) Catalyst Screening with α-Methylstyrene……………………………………………………3

1.d) Working Hypotheses…………………………………………………………………………4

2) Results and Discussion…………………………………………………………………………5

2.a) Screened Catalysts……………………………………………………………………………5

2.b) Cyclopropanation Reacions and Results……………………………………………………..6

2.c) Determination of Diastereoselectivity via ¹H NMR Analysis………………………………..7

3) Conclusions…………………………………………………………………………………...10

4) Experimental Section………………………………………………………………………….12

4.a) Diazoacetate Synthesis Procedure…………………………………………………………..12

4.b) General Cyclopropanation Reaction Procedure…………………………………………….14

4.c) Cyclopropanation Product NMR Spectra…………………………………………………...24

4.d) HPLC Traces………………………………………………………………………………..35

5) References…………………………………………………………………………………….41

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
Keyword	Styrene Cyclopropanation Diastereoselectivity Catalyst Alphamethylstyrene Dirhodium
Committee Chair / Thesis Advisor	Huw M. L. Davies, Emory University
Committee Members	Monika Raj, Emory University Yun J. Kim, Emory University

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