Expanding the scope of donor/acceptor rhodium-carbene chemistry Público
Wang, Yuxing (2015)
Abstract
The reactions of donor/acceptor rhodium carbenoids have been studied extensively in the past several decades. Cyclopropanation was a major early application of rhodium carbenoid chemistry and has been widely used in both academia and the industrial world. Also, C-H insertion by rhodium carbenoids is one of the most promising methodologies for C-H functionalization. This work attempts to expand the scope of existing rhodium carbenoid methodologies as well as develop new methodologies. The first part of this thesis describes a systematic optimization of catalyst, solvent, reaction temperature, additive, as well as reaction substrates to achieve C-H insertion of Rh(II)-stabilized carbenoids into acetals with high enantioselectivity. Eight substrates were tested under optimized conditions affording C-H insertion product in 25 - 83% yield and 87 - 94% ee. This reaction can be considered as a surrogate for the Claisen condensation. The second part of the thesis describes the development of the combined C-H functionalization/Cope rearrangement (CHCR) and C-H insertion reaction with triazoles and dihydronaphthalene. However, the reaction scope is very limited, and only a few substrates are compatible with this transformation. The last part of the thesis describes the development of an asymmetric transformation of propargylic alcohols with donor/acceptor-substituted carbenoids affording 2,5-dihydrofuran derivatives via tandem ylide formation/[2,3]-sigmatropic rearrangement/cycloisomerizaion using S-xylyl-BINAP(AuCl)2 and AgSbF6 as the catalysts.
Table of Contents
Chapter 1. Introduction. 1
1.1 Metallocarbenoid chemistry. 1
1.2 Chiral catalysts for metallocarbenoid chemistry. 4
1.3 Use of triazoles as an alternative carbene precursor.6
References. 10
Chapter 2. Asymmetric C-H insertion of Rh(II)-stabilized carbenoids into acetals: a surrogate for the Claisen condensation. 14
2.1. Introduction. 14
2.1. Results and discussion. 18
2.3. Future directions. 27
2.4. Summary. 28
References. 29
Chapter 3. Combined C-H Functionalization/Cope Rearrange Reaction with Triazoles. 31
3.1 Introduction. 31
3.1.1 CHCR reaction. 31
3.1.2 Using triazole as a mask of donor/acceptor carbenoid. 32
3.2. Results and discussion. 34
3.3. Summary. 42
References. 43
Chapter 4. Asymmetric transformations of propargyl alcohols with donor/acceptor-substituted carbenoids. 45
4.1 Introduction. 45
4.2 Results and Discussion. 48
4.3 Summary. 54
References. 55
Experimental Section. 56
General Methods. 56
Experimental Section for Chapter 2: Asymmetric C-H insertion of Rh(II) stabilized carbenoid into acetals: a surrogate for the Claisen condensation. 57
I. General procedure for C-H insertion into dioxalene. 57
II. Experimental Data. 57
Experimental Section for Chapter 3: Combined C-H Functionalization/Cope Rearrangement Reaction with Triazoles. 67
I. General procedure for Combined C-H Functionalization/Cope Rearrangement Reaction with Triazoles. 67
II. Experimental Data. 67
Experimental Section for Chapter 4: Asymmetric transformations of propargyl alcohols with donor/acceptor-substituted carbenoids. 77
I. General procedure for substituted propargyl alcohol. 77
II. General procedure for 3-silyl-substituted propargyl alcohol.77
III. General method for the gold catalyzed reaction of propargyl alcohol and aryldiazoacetates. 78
IV. Experimental Data. 78
About this Master's Thesis
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