Fotokemijske reakcije fluoriranja

Filip, Larisa (author), Iskra, Jernej (mentor)

Uvedba fluorovega atoma je zaradi njegovih specifičnih lastnosti pogosto uporabna v organski kemiji, saj značilno spremeni lastnosti spojin. Uporabnost fluoriranih spojin je zelo široka, najdemo jih v medicini, agronomiji in zadnje časa tudi v tehnologiji. Pri fluoriranju so predstavljali težavo močno reaktivni in toksični fluorirni reagenti, kar je vodilo do razvoja novih, primernejših reagentov, to pa je omogočilo enostavnejšo izvedbo fluoriranja. V diplomski nalogi sem opisala nekaj postopkov fotokemijskega fluoriranja in trifluorometiliranja. V uvodnem delu so predstavljeni pristopi k fluoriranju in reagenti, ki so se razvili za enostavnejšo izvedbo fluoriranja. V osrednjem delu so predstavljeni splošni mehanizmi, po katerih pride do fotokemijske reakcije, in opisi reakcij fluoriranja. S fotokemijskimi postopki dosežemo nekoliko milejše pogoje in s tem izvedemo reakcijo, ki je okolju prijaznejša. Najprej je predstavljena reakcija aromatskega fluoriranja, ki je bila osnovana z vezavo atoma fluora-19, potem pa so reakcijo uporabili za vezavo atoma radioizotopa fluora-18, ki je uporaben v pozitronski emisijski tomografiji. Sledijo reakcije fluoriranja na benzilnem mestu. Pri teh reakcijah lahko pride do mono- ali difluoriranja, zato so predstavljene metode obeh možnosti. Naslednje je fluoriranje alifatskih spojin, kjer se znajdemo pred novimi izzivi. Za razliko od fluoriranja na benzilnem mestu, tukaj nimamo specifičnega mesta, kamor bi se vezal fluorov atom, kar lahko povzroči težave pri selektivnosti. Reakcija, pri kateri je možno vezati fluorov atom na specifično mesto alifatske spojine, je reakcija dekarboksilativnega fluoriranja alifatskih karboksilnih spojin. Nazadnje je predstavljeno še trifluorometiliranje. Opisana so trifluorometiliranja alkenov, benzilnega mesta ter arenov in heteroaromatov. Na koncu so podane še prednosti izvajanja fotokemijskega fluoriranja v pretočnih procesih.

• Language: Slovenian
• Keywords: Fotokemijsko fluoriranje, fluor, trifluorometiliranje, fotokatalizator
• Work type: Bachelor thesis/paper
• Typology: 2.11 - Undergraduate Thesis
• Organization: FKKT - Faculty of Chemistry and Chemical Technology
• Year: 2021
• PID: 20.500.12556/RUL-130137
• COBISS.SI-ID: 82882563
• Publication date in RUL: 10.09.2021

Secondary language

• Language: English
• Title: Photochemical fluorination reactions

Abstract

Introducing the fluorine atom into organic compounds is very useful due to its specific qualities, which can cause characteristic changes of substances. Fluorinated compounds are very useful, they are found in medicine, agriculture, and lately in technology as well. During fluorination the strong reactivity and toxicity of fluorinating reagents have presented some issue. This problem has led to the development of new, more appropriate reagents, which made fluorination reactions easier. In this diploma thesis some of the reactions of photochemical fluorination and trifluoromethylation are described. In the introduction I put forward some approaches to fluorination and some fluorinating reagents that were developed to make fluorination reactions easier. Following in the main part there are general mechanisms of photochemical reactions and descriptions of reactions of fluorination. With photochemical reactions it is possible to use milder reaction conditions which therefore lead to more environment-friendly transformations. Included is a representation of aromatic fluorination, which was first performed using reagents that included atoms of fluorine-19. Later this already developed reaction was used for binding a fluorine-18 atom to the substrate, which is useful in positron emission tomography. There are some reactions of fluorination on a benzylic position. In these types of reactions, we can expect mono- or difluorination, due to this, methods for both options are introduced. The next type of reactions is fluorination of aliphatic compounds, where certain new challenges arise. Unlike benzylic fluorination, here we do not have a specific reaction site, thus leads to selectivity problems. One of the options for site-specific fluorination of aliphatic compounds is decarboxylative fluorination of aliphatic carboxylic compounds. Lastly, trifluoromethylation reactions of alkenes, benzylic positions, arenes and heteroarenes are presented. The thesis concludes by putting forward some of the advantages of carrying out the reactions in continuous flow reactors.

• Keywords: Photochemical fluorination, fluor, trifluoromethylation, photocatalyst