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

Onuska, Nicholas Paul Ralph

Abstract Details

2016, BS, Kent State University, College of Arts and Sciences / Department of Chemistry and Biochemistry.
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 molecular bend 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.
Paul Sampson, Dr. (Advisor)
Alexander Seed, Dr. (Advisor)
Ruth Leslie, Dr. (Committee Member)
Björn Lüssem, Dr. (Committee Member)
104 p.

Recommended Citations

Citations

  • Onuska, N. P. R. (2016). Studies Towards the Synthesis of 2,5-Disubstituted-3-Fluorothiophenes Using a Directed Ortho-Metalation/Nickel-Catalyzed Cross-Coupling Approach [Undergraduate thesis, Kent State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=ksuhonors1460652408

    APA Style (7th edition)

  • Onuska, Nicholas. Studies Towards the Synthesis of 2,5-Disubstituted-3-Fluorothiophenes Using a Directed Ortho-Metalation/Nickel-Catalyzed Cross-Coupling Approach . 2016. Kent State University, Undergraduate thesis. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=ksuhonors1460652408.

    MLA Style (8th edition)

  • Onuska, Nicholas. "Studies Towards the Synthesis of 2,5-Disubstituted-3-Fluorothiophenes Using a Directed Ortho-Metalation/Nickel-Catalyzed Cross-Coupling Approach ." Undergraduate thesis, Kent State University, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=ksuhonors1460652408

    Chicago Manual of Style (17th edition)