CYCLOADDITIONS AND YLIDE CHEMISTRY OF DONOR/ACCEPTOR- SUBSTITUTED CARBENES FROM THERMAL DECOMPOSITION OF ARYLDIAZOCARBONYL COMPOUNDS Público
Ovalles, Stephanie Ramona (2011)
Abstract
CYCLOADDITIONS AND YLIDE CHEMISTRY OF DONOR/ACCEPTOR-
SUBSTITUTED CARBENES FROM THERMAL DECOMPOSITION OF
ARYLDIAZOCARBONYL COMPOUNDS
By Stephanie Ramona Ovalles
It has been demonstrated that free carbenes derived from
aryldiazocarbonyl compounds
can be generated thermally in refluxing trifluorotoluene. In the
presence of alkenes, the
carbenes undergo diastereoselective cyclopropanations. Very high
diastereoselectivity
can be observed in moderate to excellent yields if the aryl group
is electron rich.
Aryldiazoketones generate ketocarbenes that undergo the Wolff
rearrangement to form
ketenes under the thermal conditions. The ketene undergoes thermal
[2+2]-cycloaddition
with alkene substrates present. Through kinetic studies, it has
been shown that electron-
withdrawing aryl groups stabilize the diazo compound. A ~100-fold
reactivity difference
was observed between nitro and methoxy-substituted
aryldiazoacetates.
The thermally generated carbenes from aryldiazoacetates undergo
ylide formation
in the presence of oxygen or nitrogen-containing substrates. This
was utilized to achieve
N-H insertions with a variety of primary and secondary amines to
afford unusual α-
amino acid precursors. Tertiary allylic and propargylic amines can
undergo a [2,3]-
sigmatropic rearrangement from the ylide to produce exotic amino
esters with α-
quaternary centers.
CYCLOADDITIONS AND YLIDE CHEMISTRY OF
DONOR/ACCEPTOR-SUBSTITUTED CARBENES FROM
THERMAL DECOMPOSITION OF ARYLDIAZOCARBONYL
COMPOUNDS
By
Stephanie Ramona Ovalles
M.A., University at Buffalo, The State University of New York,
2008
Advisor: Huw M. L. Davies, Ph.D .
A dissertation submitted to the Faculty of the
James T. Laney School of Graduate Studies of Emory University
in partial fulfillment of the requirements for the degree of
Doctor of Philosophy
in Chemistry
2011
Table of Contents
Chapter 1 Cycloaddition Chemistry of Free Donor/Acceptor
Carbenes 1
1.1 Introduction 1
1.1.1 Properties and Reactivity of Carbenes 1
1.1.2 Carbene Reactivity 2
1.1.3 Carbene Generation 5
1.1.4 Free Carbenes in Synthesis 6
1.1.5 Metal-Stabilized Donor/Acceptor-Substituted Carbenes 7
1.1.6 Cyclopropanation chemistry of Free Donor/Acceptor
Aryl-Carbenes 9
1.1.7 Electronic structure 10
1.2 Results and Discussion 12
1.2.1 Discovery 12
1.2.2 Scope of Free Carbene Cycloaddition 16
1.2.3 Mechanistic Studies of Free Carbene Generation 29
1.2.4 Thermal versus Photochemical Carbene Generation 35
1.3 Conclusions 38
Chapter 2 Ylide Chemistry of Thermally Generated
Donor/Acceptor-Carbenes 39
2.1 Introduction 39
2.1.1 Ylide Chemistry with Carbenes 39
2.1.2 N-H Insertion Chemistry 40
2.1.3 Ylide chemistry of Free Carbenes from Aryldiazoacetates
43
2.2 Results and Discussion 46
2.2.1 Initial Explorations 46
2.2.2 Thermal N-H Insertion Chemistry through Aza-ylides
51
2.2.3 N-H Insertion vs Rearrangement Chemistry 58
2.3 Future Directions 64
2.4 Conclusions 66
Chapter 3 Experimental Section 67
3.1 General Considerations 67
3.2 Procedures And Characterization Data 68
References 148
Appendix 1 NMR Spectral Data for Representative Compounds
154
Appendix 2 X-Ray Crystallographic Data 206
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