Allylic C-H Functionalization of Disubstituted Olefins via Rhodium-π-Allyl Intermediates and Development of a Chiral Cyclopentadienyl Catalyst Restricted; Files Only

Zachmann, Ashley (Spring 2019)

Permanent URL: https://etd.library.emory.edu/concern/etds/37720d65w?locale=en
Published

Abstract

Allylic C-H functionalization has been an emerging field over the last decade due to the ability to convert inert C-H bonds into C-N, C-O, and C-C bonds. In the past two years the Blakey group has developed methodology for rhodium (III) catalyzed intermolecular allylic C-H amination and etherification of 1,2-disubstituted olefins. The allylic amination methodology was found to be regioselective however was not enantioselective. Therefore it was proposed that methodology for allylic C-H alkylation of 1,2-disubstiuted olefins could be developed. Optimization for this method was done using diphenylpropene as the substrate and dimethylmalonate as the nucleophile. This methodology was found to tolerate five nucleophiles with moderate to high yields. The nucleophiles that tolerated this system contained one nitro, ketone, ester, or two esters. The regioselectivity of the system was investigated using β-alkyl-styrenederivatives and a variety of the best nucleophiles from the reaction scope with diphenylpropene. However, these reactions were found to be unsuccessful. Mechanistic studies were performed using dimethyl malonate and diphenylallyl acetate to determine if this method goes through the same mechanism as allylic amination. It was determined that product was made with only having either the rhodium or silver catalyze the reaction. This result is similar to mechanistic studies done for allylic amination and it was determined that allylic alkylation goes through the same mechanism as the allylic amination. Another goal was to develop a chiral sulfoxide cyclopentadienyl rhodium catalyst to be able to develop a new method for allylic amination that would be enantioselective. Conditions for 2,3,4,5-tertamethylcyclopenta-1,5-dien-1-yl)naphthalene ligand were first attempted to be developed through a naphthalene Grignard reaction. It was determined that by either a one-pot or two-step synthesis neither obtained the desired product. Therefore a naphthalene turbo-Grignard was then investigate and was found that desired product was made however the purification of this process is still being investigated.

Table of Contents

1.Introduction 1-6

2.Results and Discussion 6-20

2.1.Allylic C-H Alkylation 6-16

2.2.Development of a Chiral Catalyst 16-20

3.Conclusions and Future Directions 20-21

4.Supplemental Information 22-34

4.1.General Information 22-23

4.2.Material Preparation 23-34

5.References 34-36

Figures

Historical allylic functionalization via a metal π-allyl intermediate 1 Palladium catalyzed allylic C-H alkylation of terminal olefins 2             Rhodium catalyzed allylic C-H alkylation of intramolecular disubstituted olefins 2 Isolated rhodium π-allyl complexes and their reactivity 3 Allylic C-H functionalization methodologies developed in the Blakey group 4 Enantio- and regioselective allylic substitution 5 Enantioselective C-H insertion reaction 5 Trost indenylruthenium complex versus the catalyst being developed for this project 6

Tables

Optimization of dimethyl malonate with diphenylpropene 7 Reaction scope with respect to the carbon nucleophiles for allylic alkylation 9 Reaction scope of incompatible carbon nucleophiles for allylic alkylation 10 Reaction scope with phenyl β-alkyl-styrenederivative and various malonate type nucleophiles 12 Reaction scope with 4-methoxyphenyl β-alkyl-styrene derivative and various malonate type nucleophiles 13                                                                                                                           

Schemes

Conditions used for allylic C-H alkylation of disubstituted olefins 8 Proposed mechanism for rhodium catalyzed allylic C-H amination 15 Mechanistic study for allylic C-H alkylation with rhodium Cp*monomer 16 Mechanistic study for allylic C-H alkylation with silver hexafluoroantimonate 16 Proposed synthesis of chiral sulfoxide cyclopentadienyl ligand 17 Synthesis of naphthalene Grignard reagent 17 One-pot synthesis of cyclopentadienyl benzene ligand 18 One-pot synthesis of cyclopentadienyl naphthalene ligand 18 Synthesis of cyclopentadienyl naphthalene ligand from the naphthalene Grignard 19 One-pot synthesis of cyclopentadienyl naphthalene ligand from the naphthalene turbo-Grignard 20

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