Date of Award

January 2022

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Chemistry

First Advisor

Qianli Rick Chu

Abstract

Dicarboxylic acids have extensive applications in many different fields such as polymers, metal–organic materials (MOMs), and pharmaceuticals. However, many of the dicarboxylic acids currently in use are derived from nonrenewable petroleum. Recently, cyclobutane-containing dicarboxylic acids CBDAs have shown promise as biomass-derived alternatives to these petroleum-based diacids. They can be readily prepared from a number of commercially available bio-based starting materials using clean, efficient [2+2] photocycloaddition. One group of chemicals which may be utilized in producing CBDAs are the derivatives of hydroxycinnamic acid; these compounds currently have applications ranging from polymers to pharmaceuticals to cosmetics to food additives. They can be obtained from the biopolymer lignin and can thus be derived from many different biomass sources. Of particular interest among substituted hydroxycinnamic acids are ferulic acid and its derivatives, which exhibit a wide range of therapeutic effects, including anticancer, antiviral, antidiabetic, cardioprotective, neuroprotective, and anti-inflammatory activities, indicating many possible pharmaceutical applications. These compounds also possess antioxidant properties which protect against oxidative stress in cells and may slow the progression of age-related diseases, as well as reduce the risk of some types of cancer. Ferulic acid has been shown to act as a building block in polymer applications, either by itself or in its dimerized form known as incarvillateine, an example of a CBDA, which can be prepared via [2+2] cycloaddition. Incarvillateine may then be subsequently used as a component of polyamides, polyesters, and even cross polymers. Another class of compounds having great importance in organic chemistry are esters; they are present in polymers, pharmaceuticals, perfumes, flavor chemicals, fine chemicals, cosmetics, solvents, and chiral auxiliaries. Specifically, phthalate esters are commonly used as plasticizers in polymer applications; however, there is evidence that these phthalates may be toxic to the human endocrine system, and their use has come under significant scrutiny. In this study, the synthesis of a series of novel mono- and di-esters derived from CBDA-4, which are similar in structure to phthalates, may provide nontoxic alternatives. Esters of cinnamic acid derivatives, including isopropyl ferulate, isopropyl cinnamate and isopropyl p-coumarate have also been shown to readily photodimerize to form a di-ester, which may then be hydrolyzed to produce the corresponding diacid building block. Significantly, the cyclobutane ring in these esters has been shown to be thermally cleavable in the same manner as the cyclobutane ring of CBDA-4, providing a method by which materials made from them could be easily recyclable. These esters may also have potential medical applications, as other truxinate and truxillate esters have been shown to possess antinociceptive, myorelaxant, and anticancer properties. Still other truxinate and truxillate esters have been used in Ziegler-Natta catalysts for propylene polymerization, indicating that the compounds presented in this work show promising potential for use in wide-ranging applications. Still another important group of chemical compounds that find applications in nearly every field of industrial chemistry are anhydrides. They are important raw materials and intermediates employed in the manufacture of unsaturated polyester resins, surface coatings, plasticizers, copolymers, agricultural chemicals, and pharmaceuticals. For example, alkyd resins are thermoplastic polyester resins made by heating polyhydric alcohols (polyols) with dicarboxylic acids or their anhydrides. They are used in making protective coatings with good weathering properties. One such polyester known as glyptal is produced by polycondensation of glycerol and phthalic anhydride. The importance of the anhydride structure to biochemical processes has also sparked interest in anhydride research among scientists in this field. For example, succinic anhydride has been used in chemical modifications of proteins, and substituted succinimides are important pharmaceutical compounds. Many of the compounds discussed above can be derived from the biopolymer lignin, which makes up around 30% of all biomass and is the second most abundant organic polymer on earth. Lignin is an optimal source of aromatic compounds because it is renewable, has a low cost of production, and requires little processing energy, making compounds derived from it good substitutes for petroleum-based chemicals.

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