Z bakrom katalizirane reakcije spajanja za tvorbo C–C in C–heteroatom vezi

Sintič, Petra (author), Požgan, Franc (mentor)

Katalitske reakcije (križnega) spajanja so pomembne za tvorbo C–C in C–X (X = heteroatom) vezi in se uporabljajo za sintezo raznovrstnih molekul. Vlogo katalizatorja pri teh reakcijah učinkovito opravljajo kovine, še posebej paladij, platina, srebro in baker. Čeprav je paladij prevladoval v svetu reakcij spajanja, je uporaba bakra starejša od odkritja paladijevih katalizatorjev. Prve raziskave so se v veliki meri osredotočale na uporabo stehiometričnih količin bakra. Fritz Ullmann je na začetku 20. stoletja s tvorbo biarilov preko reduktivnega spajanja dveh aril halogenidov z uporabo stehiometričnih količin bakra opisal prvo obliko spajanja, ki ji danes rečemo Ullmannova reakcija. Tradicionalna različica te reakcije je znana po tem, da zahteva ostre reakcijske pogoje, ima slab izkoristek produkta in je omejena na aril halogenide s pomanjkanjem elektronov. Sodobne različice Ullmannove reakcije so začele vključevati različne ligande, ki so nudili potrebno podporo kompleksom bakrovega katalizatorja in tako omilili reakcijske pogoje in razširili obseg uporabnih substratov. Ob prelomu v 21. stoletje so se začela pojavljati številna poročila, ki so opisovala katalitske reakcije križnega spajanja na osnovi različnih bakrovih kompleksov in soli za tvorbo C–C in C–X vezi. Na plan so prišla odkritja, da lahko bakrovi katalizatorji z visoko učinkovitostjo katalizirajo reakcije križnega spajanja različnih ogranokovinskih reagentov, kot so organomagnezijevi (Grignardov reagent), organosilicijevi, organokositrovi in organoborovi z alkil, aril in heteroaril halogenidi. Razlog za vse večje zanimanje za organobakrove spojine je želja po dolgoročnih kemijskih sintezah in postopkih, saj so bakrove soli v večjih količinah prisotne v Zemljini skorji, cenejše in manj strupene v primerjavi z nekaterimi plemenitimi kovinami, kot je na primer paladij. Nizka razpoložljivost plemenitih kovin je glavni razlog za skrb, še posebej v primerih, ko je njihova poraba v porastu. Na podlagi sedanje stopnje porabe in povpraševanja po paladiju za raznovrstne reakcije, je smiselno trditi, da industrijska uporaba paladija za reakcije spajanja v prihodnje ne more ostati dolgoročno trajnostna. Ta diplomska naloga povzema zgodnja odkritja in nekaj kasnejših napredkov na področju Cu-kataliziranih reakcij (križnega) spajana pri čemer so primeri razvrščeni glede na tip vezi (C–C, C–N, C–O in C–S).

• Language: Slovenian
• Keywords: bakrov katalizator, reakcije spajanja, organokovinske in organobakrove spojine
• Work type: Bachelor thesis/paper
• Typology: 2.11 - Undergraduate Thesis
• Organization: FKKT - Faculty of Chemistry and Chemical Technology
• Year: 2022
• PID: 20.500.12556/RUL-139939
• COBISS.SI-ID: 128592899
• Publication date in RUL: 08.09.2022

Secondary language

• Language: English
• Title: Copper-catalyzed coupling reactions for the formation of C–C in C–heteroatom bonds

Abstract

(Cross) coupling reactions are important for the formation of C–C and C–X (X = heteroatom) bonds and are used for the synthesis of a wide variety of molecules. The role of a catalyst in these reactions is effectively performed by metals, especially metals such as palladium, platinum, silver and copper. Although palladium has dominated the world of coupling reactions, the use of copper predates the discovery of palladium catalysts. Early research focused largely on the use of stoichiometric amounts of copper. At the beginning of the 20th century, Fritz Ullmann described the first form of coupling, which today is called the Ullmann reaction, by forming biaryls via the reductive coupling of two aryl halides, using stoichiometric amounts of copper. The traditional version of this reaction is known to require harsh reaction conditions, has poor product yields, and is limited to electron-deficient aryl halides. Modern versions of the Ullmann reaction began to include various ligands, which provided the necessary support to the copper catalyst complexes and thus modified the reaction conditions and expanded the range of useful substrates. At the turn of the 21st century, numerous reports began to appear describing catalytic cross-coupling reactions based on various copper complexes and salts for the formation of C–C and C–X bonds. It was discovered that Cu-catalysts can perform cross-coupling reactions of various organometal reagents such as organomagnesium (Grignard reagent), organosilicon, organotin and organoboron with alkyl, aryl and heteroaryl halides with high efficiency. The reason for the increasing interest in organocopper compounds is the desire for long-term chemical syntheses and methods, since copper salts are present in larger amount in the Earth's crust, are cheaper and less toxic compared to some precious metals, such as palladium. The low availability of precious metals is a major cause of concern, especially in cases where their consumption is increasing. Based on the current level of consumption and the demand for palladium in various reactions, it is reasonable to argue that the industrial use of coupling reactions cannot remain sustainable in the long term. This thesis summarizes the early discoveries and some later advances in the field of Cu-catalyzed (cross)coupling reactions. The examples are sorted by bond type (C–C, C–N, C–O and C–S).

• Keywords: copper catalyst, coupling reactions, organometallic and organocopper compounds