Uporaba PolyHIPE polimera z vezanim paladijem za katalizo Suzuki reakcije

Ravbar, Miha (avtor), Iskra, Jernej (mentor)

V magistrskem delu smo raziskali vezavo paladija na polipiridinski trdni nosilec in njegovo uporabo kot obnovljivega katalizatorja za reakcije pripajanja. Pripravili smo heterogeni paladijev katalizator, tako da smo na polyHIPE kopolimer 4-vinilpiridina in divinilbenzena vezali paladij v obliki Pd(OAc)2. Na polimer se je vezalo 6,1% Pd oziroma 0,57 mmol Pd/g nosilca, analiza s SEM je pokazala, da se morfologija ohrani. Tak katalizator smo nato testirali na primeru Suzuki reakcije C-C pripajanja. Kot modelno reakcijo smo izbrali reakcijo med jodobenzenom in fenilborovo kislino. Testirali smo uspešnost Suzuki reakcije s tem katalizatorjem v različnih topilih, kjer se je najbolje obnesel etilen glikol monometil eter (EGME), kot bazo pa smo uporabili kalijev karbonat. Preverili smo vpliv količine katalizatorja na reakcijo s tremi različnimi molskimi deleži paladija (2,52 mol%, 1,26 mol% in 0,63 mol%) in primerjali rezultate s paladijevim acetatom. Po pričakovanjih je reaktivnost reakcije padala z nižanjem količine katalizatorja, paladijev acetat pa je bil ob enakem deležu paladija bolj aktiven od heterogenega katalizatorja. Raziskali smo tudi učinkovitost te metode na različnih substratih. Uporabili smo različno substituirane jodobenzene z elektron-donorskimi in elektron-akceptorskimi skupinami, med drugim tudi s karboksilno in aminsko skupino, in ugotovili, da reakcija bolje poteka z elektron-akceptorskimi substituenti na jodobenzenih, razen v primeru karboksilne kisline, kjer je reakcija kljub elektron-akceptorskemu značaju skupine potekala počasneje. Uporabili smo tudi nekaj različnih fenilborovih kislin, kjer je reakcija bolje potekala z elektron-donorskimi substituenti na feniliborovih kislinah, kljub temu pa se je najbolje obnesla nesubstituirana fenilborova kislina. Izkoristki produktov so bili od 66% do 93%, kjer je bila pretvorba popolna in niso potrebovali čiščenja s kolonsko kromatografijo ter med 55% in 66% pri produktih, ki jih je bilo zaradi nepopolne pretvorbe potrebno prečistiti. Naš katalizator smo poskusili tudi reciklirati in ga ponovno uporabiti v zaporednih reakcijah. Po koncu reakcije smo z razklopom polimera in sledečo atomsko absorpcijsko spektrometrijo ugotovili, da se med reakcijo paladij iz polimera spira, vendar največ v prvem koraku. Ko smo polimer uporabili za nadaljnje reakcije, je bilo spiranje manjše. Postopek smo izboljšali z vmesno regeneracijo oziroma z dodatkom diklorometana po reakciji. V prvem primeru smo nadomestili izgubljeni paladij, tako da smo polimer ponovno mešali v raztopini Pd(OAc)2, v drugem primeru pa smo z dodatkom manj polarnega topila po koncu reakcije ponovno vezali paladij, ki se je tekom reakcije raztopil. Poleg določitve količine paladija na polimeru smo posneli tudi SEM slike katalizatorja pred in po reakciji, da smo preverili strukturo polimera. Z izboljšano metodo smo zmanjšali izgubo paladija in ohranili reaktivnost heterogenega katalizatorja. Na koncu smo izvedli še sintezo bifenila direktno iz fenilborove kisline v enem koraku, tako, da smo raztopini fenilborove kisline dodali jod, kalijev karbonat in paladijev katalizator ter 24 h mešali pri 50 ºC.

• Jezik: Slovenski jezik
• Ključne besede: polyHIPE polimeri, trdni nosilci, Suzuki reakcija, heterogeni katalizator, paladijeva kataliza
• Vrsta gradiva: Magistrsko delo/naloga
• Tipologija: 2.09 - Magistrsko delo
• Organizacija: FKKT - Fakulteta za kemijo in kemijsko tehnologijo
• Leto izida: 2020
• PID: 20.500.12556/RUL-114449
• COBISS.SI-ID: 1538541251
• Datum objave v RUL: 28.02.2020

Sekundarni jezik

• Jezik: Angleški jezik
• Naslov: Use of palladium immobilized on polyHIPE polymer as a catalyst for Suzuki reaction

Izvleček

In this master thesis we studied the immobilization of palladium on a polypyridine solid support and its use as a renewable catalyst for coupling reactions. We prepared the heterogeneous palladium catalyst, by immobilizing palladium in the form of Pd(OAc)2 onto a polyHIPE copolymer of 4-vinylpyridine and divinylbenzene. The amount of Pd immobilized on the polymer was 6,1% or 0,57 mmol Pd/g, while SEM analysis showed, that the morphology of the material remained unchanged. We then tested this catalyst for the Suzuki C-C coupling reaction. As a model reaction we selected the reaction between iodobenzene and phenylboronic acid. We tested the reactivity of the Suzuki reaction using our catalyst in different solvents, where the best solvent for the reaction turned out to be ethylene glycol monomethyl ether (EGME) and as base we used potassium carbonate. We checked the effect of the amount of catalyst on the reaction using three different mol% of palladium (2,52 mol%, 1,26 mol% and 0,63 mol%) and compared that to palladium acetate. As expected the reactivity of the reaction was lower while using less catalyst and palladium acetate showed a higher activity than the heterogeneous catalyst with the same used amount. We also studied the efficiency of this method for different substrates. We used differently substituted iodobenzenes with electron-donating and electron-withdrawing groups, as among them carboxyl and amine groups, and we found that the reaction proceeds better with electron-accepting substituents on iodobenzenes, except in the case of carboxylic acid, where the reaction proceeded slower despite the electron-accepting nature of the group. We also used a few different phenylboronic acids, where the reaction proceeded better with electron-donating groups on phenylboronic acids, even though the unsubstituted phenylboronic acid turned out the best. The yields of products were 66-93% in the case where the conversion was quantitative and no purifying by column chromatography was required and 55-66% for products that had to be purified because of incomplete conversion. We also tried to recycle our catalyst and reuse it in subsequent reactions. At the end of the reaction we used digestion of the polymer and subsequent atomic absorption spectroscopy to find out that the palladium was leeching off of the polymer during the reaction, but mostly during the first use. With subsequent uses the leeching was much lower. We improved the procedure by regenerating the catalyst between reactions or by adding dichloromethane after the reaction. In the first case, we replaced the lost palladium by mixing the catalyst in a solution of Pd(OAc)2 again and in the second case we used a less polar solvent at the end of the reaction to rebind the palladium that dissolved during the reaction. Besides determining the amount of palladium on the polymer, we also took SEM pictures of the catalyst before and after the reaction to check the structure of the polymer. In the end we performed the synthesis of biphenyl directly from phenylboronic acid in one step, by adding iodine, potassium carbonate and palladium catalyst to a solution of phenylboronic acid and mixing for 24 h at 50 ºC.

• Ključne besede: polyHIPE polymers, solid supports, Suzuki reaction, heterogeneous catalyst, palladium catalysis