Photocatalyst-free wavelength-dependant sequential ring transformations of pyrazolo[1,2-a]pyrazolones

Kulašić, Ines (avtor), Petek, Nejc (avtor), Brodnik, Helena (avtor), Grošelj, Uroš (avtor), Svete, Jurij (avtor), Štefane, Bogdan (avtor)

We report sequential wavelength-selective photochemical transformations of 1-alkenylpyrazolo[1,2-a]pyrazolones to pyrazolo[1,2-a][1,2]diazepines or cyclobuta[c]pyrazolo[1,2-a]pyrazolones. Irradiation of 1-alkenylpyrazolo[1,2-a]pyrazolones with visible-light (blue LED, 457 nm) induced selective ‘ring switching’ transformation into pyrazolo[1,2-a][1,2]diazepines, which underwent electrocyclisation yielding cyclobuta[c]pyrazolo[1,2-a]pyrazolones upon irradiation with UV A light (black LED, 365 nm). Due to the very narrow irradiation wavelength now available from OLED sources, the selective formation of either 5,7-bicyclic or 5,5,4-tricyclic ring systems from the 5,5-bicyclic starting material is possible by changing the wavelength of the irradiation source. The transformations took place under mild conditions in the absence of additives or photocatalysts. Mechanistic studies indicate that these transformations proceed through the formation of an excited triplet state of the substrate, followed by selective homolytic C(1) N(8) bond cleavage, intersystem crossing, and cyclization of the zwitterionic intermediate on the ground potential energy surface. The subsequent photoinduced disrotatory stereospecific 4π-electrocyclization of the 5,7-bicyclic systems leads to 3D-rich 5,5,4-tricyclic products.

• Jezik: Angleški jezik
• Ključne besede: C-N bond cleavage, heterocycles, visible-light, ring transformation, photocatalyst-free transformations
• Vrsta gradiva: Članek v reviji
• Tipologija: 1.01 - Izvirni znanstveni članek
• Organizacija: FKKT - Fakulteta za kemijo in kemijsko tehnologijo
• Status publikacije: Objavljeno
• Različica publikacije: Objavljena publikacija
• Leto izida: 2024
• Št. strani: Str. 4441-4451
• Številčenje: Vol. 366, iss. 21
• PID: 20.500.12556/RUL-165184
• UDK: 547.77:544.52
• ISSN pri članku: 1615-4169
• DOI: 10.1002/adsc.202400684
• COBISS.SI-ID: 209299715
• Datum objave v RUL: 26.11.2024

Gradivo je del revije

• Naslov: Advanced synthesis & catalysis
• Založnik: Wiley
• ISSN: 1615-4169
• COBISS.SI-ID: 22996997

Licence

• Licenca: CC BY-NC 4.0, Creative Commons Priznanje avtorstva-Nekomercialno 4.0 Mednarodna
• Povezava: http://creativecommons.org/licenses/by-nc/4.0/deed.sl
• Opis: Licenca Creative Commons, ki prepoveduje komercialno uporabo, vendar uporabniki ne rabijo upravljati materialnih avtorskih pravic na izpeljanih delih z enako licenco.

Sekundarni jezik

• Jezik: Slovenski jezik
• Ključne besede: cepitev C-N vezi, heterocikli, vidna svetloba, pretvorbe obročev, pretvorbe brez katalizatorja

Projekti

• Financer: ARRS - Agencija za raziskovalno dejavnost Republike Slovenije
• Številka projekta: P1-0179
• Naslov: Napredna organska sinteza in kataliza