Electronic Theses and Dissertations

Date of Award

1-1-2019

Document Type

Thesis

Degree Name

M.S. in Chemistry

First Advisor

Sudeshna Roy

Second Advisor

David A. Colby

Third Advisor

John M. Rimoldi

School

University of Mississippi

Relational Format

dissertation/thesis

Abstract

The objective of the thesis is to develop regioselective methods for mono-fluorination of disubstituted triazoles, both 1,4- and 1,5-regioisomer, and isoxazoles. These strategies focus on one-pot direct access to final mono-fluorinated triazoles and isoxazoles. Eventually, these fluorinated substrates will be screened against various biological targets. Similarly, the optimization study of a regioselective method to generate 5-fluoro-1,4-disubstituted triazole was conducted. This reaction also utilized 1,3-dipolar cycloaddition to synthesize fluorinated triazole. However, difluoroalkene was used as a synthetic equivalent of fluoroalkyne for this method. This resulted into the inversion of polarity affording a different regioisomer. Here, fluoronitroalkene was identified as a synthetic equivalent of fluoroalkyne, which undergoes 1,3-dipolar cycloaddition reaction to provide a direct regioselective access to 4-fluorotriazoles. The cycloaddition of fluoro-nitroalkenes with organic azides in the presence of trifluoroacetic acid generated 4-fluoro-1,5-disubstituted triazoles regioselectively. Fluorinated heterocycles have recently received a surge of interest in the field of medicinal chemistry. An incorporation of a fluorine atom into heterocyclic compounds can influence the overall dipole moment, pKa, and hydrogen bonding patterns. Currently, there is about twenty-five percent of fluorinated drugs in the market. Among these, fluorinated nitrogen heterocycles such as isoxazoles and triazoles, have been frequently found in medicinal agents. Both triazole and isoxazole rings have shown a wide range of biological activities as anti-cancer, anti-fungal, anti-viral, anti-bacterial, and anti-diabetic. Also, a silver(I)-catalyzed reaction was studied to synthesize 4-fluoro-3,5-disubstituted isoxazole. An on-going optimization of cyclization reaction of oxime in presence of an electrophilic fluorinating source to furnish fluorinated isoxazole is discussed in detail.

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