Z natrijevim nitritom katalizirano aerobno oksidativno jodiranje aromatskih spojin

Rihtaršič, Martin (avtor), Iskra, Jernej (mentor)

Jodirane organske spojine imajo pomembno vlogo kot sintezni intermediati v organski kemiji ter zdravila in radioaktivni označevalci v medicini. Klasični jodirni reagenti so atomsko neekonomični in so tako s stališča zelene kemije neprimerni. Zato so bile narejene številne raziskave na področju oksidativnega jodiranja, ki omogoča 100 % atomsko ekonomičnost joda. V diplomskem delu smo raziskovali aerobno oksidativno jodiranje s sistemom I2/O2/NaNO2/H2SO4. Proučili smo vpliv in vlogo vsake komponente jodirnega sistema. I2 je vir jodovih atomov. O2 je terminalni oksidant, potreben za regeneracijo joda iz jodidnih ionov, ki nastanejo kot stranski produkt. NaNO2 v prisotnosti kisline disproporcionira na dušikove okside, ki so posredniki elektronov med jodidnimi ioni in kisikom v katalitskem ciklu regeneracije joda. Hkrati katalitski cikel lahko omogoči in situ tvorbo elektrofilnega »I+« reagenta, ki reagira z nukleofilnim organskim substratom. H2SO4 je aktivator jodiranja, saj omogoči tvorbo dušikovih oksidov iz NaNO2. Z jodirnim sistemom smo v kisikovi atmosferi pri sobni temperaturi monojodirali anizol, 4-terc-butilfenol in 4-terc-butiltoluen. Anizol se s substehiometričnimi količinami H2SO4 po 3 urah kvantitativno pretvori v monojodiran produkt; 4-jodoanizol smo izolirali z 82 % izkoristkom, pri tem pa nismo potrebovali organskih topil. 4-terc-Butilfenol s sistemom ni kompatibilen zaradi stranske reakcije oksidativnega nitriranja – zaradi porabljanja NO2 se katalitski cikel ustavi in kvantitativna pretvorba v jodiran produkt ni mogoča. Po kromatografski ločbi reakcijske zmesi je bil izkoristek dobljenega jodiranega produkta 34 %. 4-terc-Butiltoluen je za jodiranje manj aktiviran, a je pretvorba kvantitativna ob povečanju količine H2SO4 in podaljšanju reakcijskega časa na 24 ur. Izkoristek jodiranja je 95 %. Metoda uporablja dostopen vir jodovih atomov I2, »zelen« oksidant O2 in poceni katalizator NaNO2. Reakcija poteka pri sobni temperaturi, reakcijski medij pa je ekološko sprejemljiv MeCN. Sistem je primeren za jodiranje aktiviranih aromatskih spojin, njegovo reaktivnost pa uravnavamo s koncentracijo H2SO4.

• Jezik: Slovenski jezik
• Ključne besede: oksidativno halogeniranje, aerobno jodiranje, kisik, dušikovi oksidi, zelena kemija
• Vrsta gradiva: Diplomsko delo/naloga
• Tipologija: 2.11 - Diplomsko delo
• Organizacija: FKKT - Fakulteta za kemijo in kemijsko tehnologijo
• Leto izida: 2021
• PID: 20.500.12556/RUL-129956
• COBISS.SI-ID: 82509315
• Datum objave v RUL: 09.09.2021

Sekundarni jezik

• Jezik: Angleški jezik
• Naslov: Aerobic oxidative iodination of aromatic molecules catalyzed with sodium nitrite

Izvleček

Iodinated organic compounds have a crucial role as synthetic intermediates in organic chemistry, as well as drugs and radioactive markers in medicine. Classic iodinating agents have low atom economy and as such are unsuitable from a green chemistry perspective. Therefore, abundant research has been conducted on the field of oxidative iodination, which enables 100 % iodine atom economy. Within this Bachelor's thesis, aerobic oxidative iodination with I2/O2/NaNO2/H2SO4 system is studied. Influence and role of each component in our system was investigated. I2 is the source of iodine atoms. O2 is the terminal oxidant for iodine regeneration from iodide ions that form as a side product. Under acidic conditions, NaNO2 disproportionates to nitric oxides that act as electron mediators between iodide ions and oxygen in the catalytic cycle of iodine regeneration. Furthermore, the catalytic cycle can enable in situ formation of electrophilic »I+« reagent that reacts with nucleophilic organic substrate. H2SO4 is the activator of iodination, as it enables the formation of nitric oxides from NaNO2. Using our system, anisole, 4-tert-butylphenol and 4-tert-butyltoluene were monoiodinated at room temperature in oxygen atmosphere. Anisole is quantitatively converted to monoiodinated product in 3 hours; 4-iodoanisole was isolated with 82 % yield without the use of organic solvents. 4-tert-Butylphenol is incompatible with our system due to oxidative nitration side reaction – depletion of NO2 halts the catalytic cycle, thus making quantitative conversion to iodinated product unattainable. Isolated yield of iodinated product was 34 % after chromatographic separation. Although 4-tert-butyltoluene is less activated for iodination, quantitative conversion was achieved by employing higher concentration of H2SO4 and longer reaction time (24 hours). Yield of iodination was 95 %. Our method utilizes accessible iodine atom source I2, »green« oxidant O2, and inexpensive catalyst NaNO2. Reaction is conducted at room temperature in environmentally acceptable MeCN. Our system is suitable for iodination of activated aromatic compounds, and its reactivity can be readily tuned by adjusting the concentration of H2SO4.

• Ključne besede: oxidative halogenation, aerobic iodination, oxygen, nitric oxides, green chemistry