Impact of Silyl Ethyl Esters on the Rhodium(II)-Catalyzed Transformations of Donor/Acceptor Carbenes Pubblico

Abstract

Donor/acceptor carbenes are a privileged class of reagents that are capable of highly site-selective C-H bond functionalization when used in combination with transition metal catalysts. This ability to selectively functionalize a C-H bond has revolutionized organic synthesis in recent years. The transformations of a donor/acceptor carbene substituted with a trialkylsilyl moiety in the acceptor group are investigated. It was discovered that in the presence of the catalyst Rh2(TPA)4, triisopropylsilyl-substituted ethyl aryldiazoacetates undergo an intramolecular C-H insertion followed by decomposition of the beta-lactone intermediate, resulting in preferential formation of the more sterically hindered Z allylsilanes. In addition to this unexpected reactivity, the silyl substituted donor/acceptor carbenes are excellent substrates for cyclopropanation using Rh2(S-DOSP)4. This reaction has been applied to the synthesis of the triarylcyclopropane carboxylate ligand used in the catalyst Rh2(R-BTPCP)4.

Table of Contents

Table of Contents Page

Introduction...................................................................................................1

Part 1: Reaction of a Silyl-Substituted Diazo Compound........................................11

Background: Allylsilanes.................................................................................12

Exploration of a New Allylsilane Reaction...........................................................14 Discussion....................................................................................................22

Part 2: Cyclopropanation.................................................................................25

Exploration of Ligand Synthesis........................................................................30 Conclusion....................................................................................................30

Experimental Data.........................................................................................32

Figures

1. Three classes of carbenes.............................................................................3

2. Structure of dirhodium(II) tetracarboxylate catalysts.........................................4

3. Dirhodium tetracarboxylate catalysts..............................................................5

4. Structure of Rh2(R-BTPCP)4...........................................................................7

5. Silyl substituted ethyl aryldiazoacetate............................................................8

6. Example cyclopropane natural product............................................................9

7. Structure of Rh2(TPA)4................................................................................16

Tables

1. Catalyst Optimization Study.........................................................................15

2. Initial Investigation of Reaction Scope............................................................17

3. Silyl Group Optimization..............................................................................18

4. Catalyst Optimization for Cyclopropanation.....................................................27

5. Exploration of Substrate Scope.....................................................................28

6. Substrate Scope with Optimized Conditions.....................................................29

Schemes

1. Synthesis of triarylcyclopropanecarboxylate ligand............................................8

2. Reaction of a silyl substituted diazo with Rh2(S-DOSP)4.....................................11

3. Control reaction for byproduct identification....................................................12

4. Exploration of Diazo Substrate Scope.............................................................20

5. Synthesis of Chiral Allylsilanes......................................................................21

6. General Synthesis of Diazo Compounds..........................................................22

7. Proposed Mechanism for Allylsilane Formation.................................................23

8. Control Reaction to Isolate Beta-lactone Intermediate.......................................23

9. Explanation of Observed Stereochemistry.......................................................25

10. Synthesis of Triarylcyclopropanecarboxylate..................................................30

About this Honors Thesis

Rights statement

• Permission granted by the author to include this thesis or dissertation in this repository. All rights reserved by the author. Please contact the author for information regarding the reproduction and use of this thesis or dissertation.

School	Emory College
Department	Chemistry
Degree	BS
Submission	Honors Thesis
Language	English
Research Field	Chemistry, Organic
Parola chiave	Allylsilanes Cyclopropanation Carbenes Organic Synthesis Rhodium(II)
Committee Chair / Thesis Advisor	Davies, Huw, Emory University
Committee Members	Pratt, Louise, Emory University Blakey, Simon, Emory University

Ultima modifica

Primary PDF

Thumbnail	Title	Date Uploaded	Actions
	Impact of Silyl Ethyl Esters on the Rhodium(II)-Catalyzed Transformations of Donor/Acceptor Carbenes ()	2018-08-28 14:53:07 -0400	Press to Select an action Download

Supplemental Files

Thumbnail	Title	Date Uploaded	Actions