Fotoredoks katalitske pretvorbe triklorometansulfenil klorida

Zorko, Tilen (author), Štefane, Bogdan (mentor)

Fotokemija omogoča pretvorbe, ki dopolnjujejo tradicionalne dvoelektronske reakcije in odpirajo vrata sinteznim pretvorbam, ki so bile nekoč zahtevne ali nedostopne. Pogost primer fotokemijske reakcije je adicija radikalov s prenosom atomov (ATRA), ki predstavlja enostaven način uvedbe različnih funkcionalnih skupin na alkene in alkine. V raziskavi smo reakcijo uspešno uporabili za uvedbo triklorometilsulfenilne skupine in s tem razvili novo metodo triklorometilsulfeniliranja alkenov. Triklorometilsulfenilno skupino smo na alkene uvajali s komercialno dostopnim reagentom triklorometilsulfenil kloridom. Izvedli smo mehanistične študije in ugotovili, da reakcija poteka po radikalskem mehanizmu induciranem s svetlobo primerne valovne dolžine. Meritev kvantnega izkoristka je pokazala, da prevladujoč mehanizem predstavlja radikalska propagacija, kar naredi reakcijo bolj aplikativno za potencialno uporabo v industriji. Reakcijo smo testirali tudi v prisotnosti lovilcev radikalov, pri čemer se je izkoristek pretvorbe močno znižal, hkrati pa nam je z uporabo masne spektrometrije uspelo dokazati prisotnost aduktov reakcijskih intermediatov s (2,2,6,6-tetrametilpiperidin-1-il)oksil radikalom (TEMPO). Deloma lahko reakcija poteče tudi brez prisotnosti fotoobčutljivcev, vendar so v tem primeru izkoristki nižji, reakcija pa poteka bistveno počasneje. Slednje smo pojasnili iz absorbančnega spektra triklorometansulfenil klorida, ki šibko absorbira modro svetlobo, kar lahko privede do homolitske cepitve vezi in sproži radikalsko propagacijo. Najvišje izkoristke smo dobili pri uporabi fotokatalizatorjev na osnovi bakrovih kompleksov, ki predvsem zaradi nizke cene in dostopnosti v zadnjih letih pridobivajo na pomenu. Triklorometilsulfenilne produkte smo izolirali z hitro kolonsko kromatografijo ali destilacijo pod znižanim tlakom. Izolacija z normalno fazno kolonsko kromatografijo se je v večini primerov izkazala za neprimerno, saj produkti počasi razpadajo na silikagelu.

• Language: Slovenian
• Keywords: fotoredoks kemija, radikalska verižna reakcija, ATRA, sulfeniliranje
• Work type: Master's thesis/paper
• Typology: 2.09 - Master's Thesis
• Organization: FKKT - Faculty of Chemistry and Chemical Technology
• Year: 2024
• PID: 20.500.12556/RUL-161248
• COBISS.SI-ID: 207396355
• Publication date in RUL: 09.09.2024

ZORKO, Tilen, 2024, Fotoredoks katalitske pretvorbe triklorometansulfenil klorida [online]. Master’s thesis. [Accessed 14 April 2025]. Retrieved from: https://repozitorij.uni-lj.si/IzpisGradiva.php?lang=eng&id=161248

Secondary language

• Language: English
• Title: Photoredox catalytic transformations of trichloromethanesulfenyl chloride

Abstract

Photochemistry opens doors to transformations that complement traditional two-electron reactions and enable conversions that were once challenging or inaccessible. One common example of a photochemical reaction is the addition of radicals with atom transfer (ATRA), which provides a straightforward method for introducing various functional groups onto alkenes and alkynes. In our research, we successfully utilized this reaction to introduce the trichloromethylsulfenyl group, thereby developing a novel method for its incorporation into various alkenes. The trichloromethylsulfenyl group was introduced onto alkenes using a commercially available reagent, trichloromethylsulfenyl chloride. Mechanistic studies revealed that the reaction proceeds through a radical mechanism and requires light. Quantum yield measurements indicated that the predominant mechanism involves radical propagation, enhancing the practical applicability of the reaction in industry. We conducted experiments testing the reaction in the presence of radical scavengers, which led to a significant reduction in yields. Additionally, through mass spectrometry analysis, we confirmed the presence of adducts of reaction intermediates with (2,2,6,6-tetramethylpiperidin-1-yl)oxyl radical (TEMPO). We also observed that the reaction partially occurs even without photo sensitizers, albeit with lower yields and slower kinetics. This was attributed to the weak absorption of blue light by trichloromethylsulfenyl chloride, potentially triggering homolytic bond cleavage and radical propagation. Trichloromethylsulfenyl products were isolated using flash chromatography and distillation under reduced pressure, while isolation using normal-phase column chromatography proved unsuitable, as most of the products degraded slowly on silica gel.

• Keywords: Photoredox Chemistry, Radical Chain Reaction, ATRA, Sulfenylation