Fotoredoks katalitske pretvorbe pirazolov

doktorska disertacija

Nejc Petek (Author), Bogdan Štefane (Mentor), Jernej Iskra (Thesis defence commission member), Janez Mravljak (Thesis defence commission member), Stojan Stavber (Thesis defence commission member)

Abstract

Redoks reakcije, ki potečejo po absorpciji fotonov, omogočajo pripravo in funkcionalizacijo heterocikličnih spojin pod blagimi reakcijskimi pogoji. Od teh smo se osredotočili na pretvorbe spojin s pirazolnim skeletom. Pod vidno svetlobo v prisotnosti fotoredoks katalizatorja eozina ter kisika kot oksidanta smo uspešno oksidirali 1-substituirane pirazolidin-3-one. Nastali azometin imini so uporabni gradniki v sintezi heterocikličnih spojin, kar smo pokazali z enolončno reakcijo fotokatalizirane oksidacije ter cikloadicije nastalih dipolov z inoni. Po optimizaciji reakcijskih pogojev smo tako sintetizirali nabor azometin iminov ter pirazolo[1,2-a]pirazolov. Uspešno smo oksidirali tudi 1-arilpirazolidin-3-one do pirazol-3-onov. Kot stranske produkte oksidacije pirazolidin-3-onov smo identificirali aldehide ter ketone, ki nastanejo iz substituenta na mestu N1 tvorjenih azometin iminov. Pirazolo[1,2-a]pirazoli absorbirajo vidno svetlobo, pri čemer tudi fluorescirajo. Izmerili smo nekatere optične lastnosti teh bicikličnih spojin ter prvič pripisali izpostavljenost svetlobi kot vzrok za njihovo nestabilnost v raztopini, kjer pride do odpiranja enega od pirazolnih obročev. Z optimizacijo reakcijskih pogojev smo dosegli kar 6 selektivnih pretvorb v različno substituirane pirazole. Potek reakcij je odvisen od substituentov na pirazolo[1,2-a]pirazolnem obroču ter dodanih reagentov. Predstavljene raziskave so ključnega pomena za uporabo pirazolo[1,2-a]pirazolov kot fluorescentnih označevalcev. Pirazole smo poskusili sulfonirati s fotoredoks katalizirano radikalsko adicijo. Pri tem smo uporabili sulfonil kloride, prav tako pridobljene pod fotoredoks katalitskimi pogoji. Izbranih heterocikličnih spojin nismo uspeli funkcionalizirati. Raziskavo smo zaključili z nepričakovano odkrito dvostopenjsko tvorbo dialkenil sulfonov z zaporednima radikalskima adicijama med triflil kloridom ter arilacetileni. Transformacija kljub znanim sorodnim reakcijam med triflil kloridom ter alkeni še ni bila raziskana.

Keywords

fotokemija;pirazoli;pirazolo[1,2-a]pirazoli;pirazolidin-3-oni;fotoredoks kataliza;fotokatalizatorji;vidna svetloba;fotoreakcije;doktorske disertacije;

Data

Language:	Slovenian
Year of publishing:	2021
Typology:	2.08 - Doctoral Dissertation
Organization:	UL FKKT - Faculty of Chemistry and Chemical Technology
Publisher:	[N. Petek]
UDC:	547.86:544.526:543.242/.243(043.3)
COBISS:	82212611
Views:	374
Downloads:	96
Average score:	0 (0 votes)
Metadata:

Other data

Secondary language:	English
Secondary title:	Photoredox catalytic transformations of pyrazoles
Secondary abstract:	Redox reactions, which take place after photon absorption, enable preparation and functionalization of heterocyclic compounds under mild reaction conditions. Out of those, we focused our attention on the transformations of pyrazole-based compounds. Under visible light irradiation in the presence of eosin, a photoredox catalyst, and oxygen, an oxidant, 1-substituted pyrazolidin-3-ones were successfully oxidized. So formed azomethine imines are useful building blocks in the synthesis of heterocyclic compounds, as demonstrated by a one-pot photocatalyzed oxidation and cycloaddition of ensuing dipoles with ynones. After optimization of reaction conditions, a plethora of azomethine imines and pyrazolo[1,2-a]pyrazoles were synthesized. 1-Arylpyrazolidin-3-ones were also successfully oxidized to 1-arylpyrazol-3-ones. Aldehydes and ketones, which are formed from N1 substituent of azomethine imines, were identified as side products of pyrazolidin-3-one oxidation. Pyrazolo[1,2-a]pyrazoles are fluorescent compounds, which can absorb visible light. Some of the optical properties of these bicyclic compounds were measured. Their instability in solutions was for the first time attributed to exposure to visible light as pyrazole ring opening takes place. With optimization of reaction conditions, 6 distinct transformations into substituted pyrazoles were achieved. The selectivity of the reactions is dependent on the substituents on the pyrazolo[1,2-a]pyrazole and the added reagents. The combined research proved crucial in the use of pyrazolo[1,2-a]pyrazoles as fluorescent markers. Attempts to sulfonate pyrazoles with photoredox catalyzed radical addition with sulfonyl chlorides, which were synthesized under photoredox catalyzed conditions as well, were unsuccessful. The research was concluded with an unexpected two-step formation of dialkenyl sulfones with sequential radical additions between triflyl chloride and arylacetylenes. This transformation has not yet been explored despite already investigated reactions involving alkenes.
Secondary keywords:	pyrazoles;pyrazolo[1,2-a]pyrazoles;photoredox catalysis;visible light;photoreactions;
Type (COBISS):	Doctoral dissertation
Study programme:	1000381
Embargo end date (OpenAIRE):	1970-01-01
Thesis comment:	Univ. v Ljubljani, Fak. za kemijo in kemijsko tehnologijo
Pages:	147 str.
ID:	13587578