Structural Requirements of the Sulfonyl Prolinate Ligands for Dirhodium Catalysis Open Access

Abstract

Previous experimental studies have indicated that arylsulfonyl prolinate ligands might be a structural requirement in dirhodium tetraprolinate catalysis. The research presented here expands upon and tests this notion using aryl carbene precursors and two N-alkylsulfonyl prolinate catalysts, N-dodecylsulfonyl and N-methylsulfonyl. The results of this research demonstrate that arylsulfonyl prolinate ligands are not a structural requirement for achieving high enantioselectivity in cyclopropanation and C-H functionalization reactions. Currently, extensive computational studies are in progress by other members of the Davies group to develop a new model to explain the enantioselectivity of the N-sulfonylprolinate catalysts. The experimental data presented herein show that an alkylsulfonyl prolinate ligand is similarly effective at asymmetric induction as the arylsulfonyl derivatives used previously. Therefore, the new model from the computational calculations will need to address the notion that the aryl component of the sulfonyl ligand is not a critical requirement for achieving high asymmetric induction.  

Table of Contents

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

1.1. The Requirement of Stereoselective Synthesis in Chemistry…………………………………………1

1.2. Carbene Formation with Diazoacetates and Diazo Modification Effect on Selectivity……3

1.3. Two major Types Reactions for Donor-Acceptor Carbenes: Cyclopropanation and C-H Functionalization Reactions……………………………………………………………………………………………5

1.4. Symmetric Models for Dirhodium Catalyst……………………………………………………………………7

1.5. Previous Mechanism for Stereochemical Control in Dirhodium Tetraprolinate Catalysis…………………………………………………………………………………………………………………………8

2. Exploration of the Structural Requirements of the Sulfonyl Prolinate Ligands for Dirhodium Catalysis…………………………………………………………………………………………………………………………………..10

2.1. Synthesis of N-methylsulfonyl Catalyst for C-H functionalization reactions……………………….12

2.2. N-arylsulfonyl Catalyst Screening via Cyclopropanation Reactions……………………………………13

2.3. N-alkylsulfonyl Catalyst Screening via Cyclopropanation Reactions…………………………………15

2.4. Diazoacetate Screen via N-methyl/dodecylsulfonyl Catalyzed Cyclopropanations……………18

2.5. Dirhodium Tetraprolinate Catalyzed C-H Functionalization Reactions………………………………20

3. Conclusions………………………………………………………………………………………………………………………….29

4. Experimental………………………………………………………………………………………………………………………30

4.1. General Remarks……………………………………………………………………………………………………………….30

4.2. General Procedure for the Synthesis of Diazoacetates………………………………………………………30

4.3. N-methylsulfonyl Catalyst Synthesis…………………………………………………………………………………32

4.4. General Procedure for Cyclopropanation Reactions with Methyl 2-diazo-2-phenylacetate.34

4.5. General Procedure for Cyclopropanation Reactions in Diazo Screen…………………………………50

4.6. General Procedure for C-H Functionalization Reactions with N-dodecyl/methyl Catalyst…65

4.7. General Procedure for C-H Functionalization Reactions with R-(DOSP)4……………………………81

5. References……………………………………………………………………………………………………………………………91

Figures and Tables

Figure 1.1.1………………………………………………………………………………………………………………………………..1

Figure 1.1.2………………………………………………………………………………………………………………………………..2

Figure 1.1.3………………………………………………………………………………………………………………………………..2

Figure 1.2.1………………………………………………………………………………………………………………………………..3

Figure 1.2.2………………………………………………………………………………………………………………………………..4

Figure 1.3.1………………………………………………………………………………………………………………………………..6

Figure 1.3.2………………………………………………………………………………………………………………………………..7

Figure 1.4.1………………………………………………………………………………………………………………………………..7

Figure 1.4.2………………………………………………………………………………………………………………………………..8

Figure 1.5.1………………………………………………………………………………………………………………………………..9

Figure 2a….………………………………………………………………………………………………………………………………10

Figure 2b….………………………………………………………………………………………………………………………………11

Figure 2.1.1………………………………………………………………………………………………………………………………12

Table 2.2.1……………………………………………………………………………………………………………………………….14

Table 2.3.1……………………………………………………………………………………………………………………………….16

Table 2.3.2……………………………………………………………………………………………………………………………….17

Figure 2.4.1………………………………………………………………………………………………………………………………18

Figure 2.4.2………………………………………………………………………………………………………………………………20

Figure 2.5.1………………………………………………………………………………………………………………………………21

Figure 2.5.2………………………………………………………………………………………………………………………………22

Figure 2.5.3………………………………………………………………………………………………………………………………23

Figure 2.5.4………………………………………………………………………………………………………………………………24

Figure 2.5.5………………………………………………………………………………………………………………………………25

Figure 2.5.6………………………………………………………………………………………………………………………………25

Figure 2.5.7………………………………………………………………………………………………………………………………26

Figure 2.5.8………………………………………………………………………………………………………………………………27

Figure 2.5.9………………………………………………………………………………………………………………………………28

About this Honors Thesis

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School	Emory College
Department	Chemistry
Degree	B.A.
Submission	Honors Thesis
Language	English
Research Field	Chemistry, Organic
Keyword	alkylsulfonyl ligands dirhodium tetraprolinate catalysts
Committee Chair / Thesis Advisor	Dr. Huw Davies, Emory University
Committee Members	Dr. Kate O'Toole, Emory University Dr. John Heemstra, Jr. , Emory University

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