Studies Towards the Synthesis of 2,5-Disubstituted-3-Fluorothiophenes Using a Directed Ortho-Metalation/Nickel-Catalyzed Cross-Coupling Approach

Studies Towards the Synthesis of 2,5-Disubstituted-3-Fluorothiophenes Using a Directed Ortho-Metalation/Nickel-Catalyzed Cross-Coupling Approach

Bibliographic Details
Main Author: Onuska, Nicholas Paul Ralph
Language:English
Published: Kent State University Honors College / OhioLINK 2016
Subjects:
Chemistry
Organic chemistry
liquid crystals
cross-couplings
nickel cross-couplings
suzuki couplings
directed ortho metalation
organometallic chemistry
Online Access:http://rave.ohiolink.edu/etdc/view?acc_num=ksuhonors1460652408
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spelling ndltd-OhioLink-oai-etd.ohiolink.edu-ksuhonors14606524082021-08-03T06:35:32Z Studies Towards the Synthesis of 2,5-Disubstituted-3-Fluorothiophenes Using a Directed Ortho-Metalation/Nickel-Catalyzed Cross-Coupling Approach Onuska, Nicholas Paul Ralph Chemistry Organic chemistry liquid crystals cross-couplings nickel cross-couplings suzuki couplings directed ortho metalation organometallic chemistry 2,5-Disubstituted 3-fluorothiophene derivatives are of particular interest as potential liquid crystal materials. When compared to liquid crystal materials based on phenyl systems, thiophene-based liquid crystals often have improved physical properties, such as lower viscosity and faster switching times. Additionally, the small molecularbend of thiophene-based systems reduces molecular packing and therefore melting point. Incorporation of fluorine into liquid crystal materials allows for the properties of the material to be fine-tuned. In addition to increasing the lateral dipole moment of the molecule due to the high electronegativity of fluorine, the low polarizability of fluorine reduces intermolecular dispersion forces. In aromatic chemistry, the synthesis of 1,2-disubsituted aromatic systems is often challenging. However, through a process known as directed ortho metalation (DOM), an aromatic system may be selectively deprotonated using an alkyllithium base and trapped with an electrophile to yield a 1,2-disubstituted product. The effectiveness of this process hinges on the ability of the alkyllithum base to coordinate to the existing aromatic substituent, known as a directed metalation group (DMG). There may be a mixture of substituted material and protodemetalated material present after addition of the desired electrophile. In the case of fluorination, the fluorinated and protodemetalated products are typically difficult to separate by conventional purification techniques. The goal of this project was to explore new synthetic approaches to fluorinated thiophene-based building blocks that could be incorporated into liquid crystal synthesis.This project entails the synthesis of 2-thienyl carbamate materials which we hypothesized may be sequentially fluorinated and then subjected to nickel-catalyzed Suzuki-type coupling to yield the desired 2,5-disubstituted 3-fluorothiophene targets. 2016-05-09 English text Kent State University Honors College / OhioLINK http://rave.ohiolink.edu/etdc/view?acc_num=ksuhonors1460652408 http://rave.ohiolink.edu/etdc/view?acc_num=ksuhonors1460652408 unrestricted This thesis or dissertation is protected by copyright: all rights reserved. It may not be copied or redistributed beyond the terms of applicable copyright laws.
collection NDLTD
language English
sources NDLTD
topic Chemistry
Organic chemistry
liquid crystals
cross-couplings
nickel cross-couplings
suzuki couplings
directed ortho metalation
organometallic chemistry
spellingShingle Chemistry
Organic chemistry
liquid crystals
cross-couplings
nickel cross-couplings
suzuki couplings
directed ortho metalation
organometallic chemistry
Onuska, Nicholas Paul Ralph
Studies Towards the Synthesis of 2,5-Disubstituted-3-Fluorothiophenes Using a Directed Ortho-Metalation/Nickel-Catalyzed Cross-Coupling Approach
author Onuska, Nicholas Paul Ralph
author_facet Onuska, Nicholas Paul Ralph
author_sort Onuska, Nicholas Paul Ralph
title Studies Towards the Synthesis of 2,5-Disubstituted-3-Fluorothiophenes Using a Directed Ortho-Metalation/Nickel-Catalyzed Cross-Coupling Approach
title_short Studies Towards the Synthesis of 2,5-Disubstituted-3-Fluorothiophenes Using a Directed Ortho-Metalation/Nickel-Catalyzed Cross-Coupling Approach
title_full Studies Towards the Synthesis of 2,5-Disubstituted-3-Fluorothiophenes Using a Directed Ortho-Metalation/Nickel-Catalyzed Cross-Coupling Approach
title_fullStr Studies Towards the Synthesis of 2,5-Disubstituted-3-Fluorothiophenes Using a Directed Ortho-Metalation/Nickel-Catalyzed Cross-Coupling Approach
title_full_unstemmed Studies Towards the Synthesis of 2,5-Disubstituted-3-Fluorothiophenes Using a Directed Ortho-Metalation/Nickel-Catalyzed Cross-Coupling Approach
title_sort studies towards the synthesis of 2,5-disubstituted-3-fluorothiophenes using a directed ortho-metalation/nickel-catalyzed cross-coupling approach
publisher Kent State University Honors College / OhioLINK
publishDate 2016
url http://rave.ohiolink.edu/etdc/view?acc_num=ksuhonors1460652408
work_keys_str_mv AT onuskanicholaspaulralph studiestowardsthesynthesisof25disubstituted3fluorothiophenesusingadirectedorthometalationnickelcatalyzedcrosscouplingapproach
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