Link to the University of Pittsburgh Homepage
Link to the University Library System Homepage Link to the Contact Us Form

Regulating Reactivity and Selectivity of a Dehydro-Diels–Alder Reaction of Vinyl Heteroarenes Informed by Mechanism and Application towards the Synthesis of Photovoltaic Materials

Winkelbauer, Joseph (2021) Regulating Reactivity and Selectivity of a Dehydro-Diels–Alder Reaction of Vinyl Heteroarenes Informed by Mechanism and Application towards the Synthesis of Photovoltaic Materials. Doctoral Dissertation, University of Pittsburgh. (Unpublished)

[img] PDF
Restricted to University of Pittsburgh users only until 8 October 2022.

Download (27MB) | Request a Copy

Abstract

Ring-fused heteroarenes are present in numerous natural products, FDA approved drugs, agrochemicals, and recently, organic solar cells able to achieve record breaking power conversion efficiencies. Access to these valuable compounds relies primarily on synthesis with dearomative cycloadditions of heteroarenes emerging as an efficient strategy. Many of these reactions require forceful conditions that utilize catalysts, acids and bases, or high temperatures to effect dearomatization. We have developed an intramolecular dearomative didehydro-Diels–Alder (DDDA) reaction which proceeds at temperatures as low as 60 °C with mild conditions, free of additives or catalysts. The adduct of the dearomative cycloaddition, which has been isolated and characterized, readily rearomatizes to either an isomerization product by way of a hydrogen migration or an oxidation product by way of a dehydrogenation.
To determine the substrate dependent factors that control the dearomative cycloaddition, kinetic studies were conducted with in situ reaction monitoring by ReactIR and afforded experimental Gibbs free energies of activation which correlated well with DFT calculations to reveal a highly asynchronous, concerted transition state. Aromaticity of the heteroarene, tether composition, and dispersion interactions were identified as substrate dependent factors that affect reactivity, establishing DFT calculations as a predictive tool in determining reactivity.
For the first time, the 1,4-cyclohexadienyl DA adduct was isolated, characterized, and confirmed as the product of the dearomative cycloaddition with divergent reactivity from the adduct leading to formation of either oxidation or isomerization products. These divergent mechanisms were investigated, and product selectivity was enhanced with control over the reaction parameters. Experiments utilizing deuterium oxide or increased exposure to air revealed the isomerization products were formed by an intermolecular, ionic proton transfer, while oxidation products were formed by an oxygen promoted dehydrogenation. Selectivity for either product was enhanced through reaction parameters such as temperature, solvent polarity, concentration, atmosphere, and additives.
Insight into the mechanisms of dearomatization and product formation allowed us to enhance the reactivity and product selectivity of the dearomative DDDA reaction for vinyl heteroarenes which was then applied towards the synthesis of ladder-type heteroarenes for organic photovoltaic materials. We expect these mechanistic findings to lend insight into other dearomative processes in the future.


Share

Citation/Export:
Social Networking:
Share |

Details

Item Type: University of Pittsburgh ETD
Status: Unpublished
Creators/Authors:
CreatorsEmailPitt UsernameORCID
Winkelbauer, Josephjaw242@pitt.edujaw242
ETD Committee:
TitleMemberEmail AddressPitt UsernameORCID
Committee ChairBrummond, Kaykbrummon@pitt.edukbrummon0000-0003-3595-6806
Committee MemberFloreancig, Paulflorean@pitt.eduflorean0000-0001-9626-3187
Committee MemberHorne, Sethhorne@pitt.eduhorne0000-0003-2927-1739
Committee MemberBernhard, Stefanbern@cmu.edu0000-0002-8033-1453
Date: 8 October 2021
Date Type: Publication
Defense Date: 5 May 2021
Approval Date: 8 October 2021
Submission Date: 12 May 2021
Access Restriction: 1 year -- Restrict access to University of Pittsburgh for a period of 1 year.
Number of Pages: 429
Institution: University of Pittsburgh
Schools and Programs: Dietrich School of Arts and Sciences > Chemistry
Degree: PhD - Doctor of Philosophy
Thesis Type: Doctoral Dissertation
Refereed: Yes
Uncontrolled Keywords: Diels Alder Dearomative Heteroarene Kinetic ReactIR Reactivity activation energy gibbs free transition state mechanism computational brummond rate product selectivity
Date Deposited: 08 Oct 2021 19:50
Last Modified: 08 Oct 2021 19:50
URI: http://d-scholarship.pitt.edu/id/eprint/41075

Metrics

Monthly Views for the past 3 years

Plum Analytics


Actions (login required)

View Item View Item