In this paper, we report on a one-step catalyst-transfer macrocyclization (CTM) reaction, based on the Pd-catalyzed Buchwald-Hartwig cross-coupling reaction, selectively affording only cyclic structures. This route offers a versatile and efficient approach to synthesize aza[1(n)]paracyclophanes (APCs) featuring diverse functionalities and lumens. The method operates at mild reaction temperatures (40 degrees C) and short reaction times (similar to 2 h), delivering excellent isolated yields (>75% macrocycles) and up to 30% of a 6-membered cyclophane, all under nonhigh-dilution concentrations (35-350 mM). Structural insights into APCs reveal variations in product distribution based on different endocyclic substituents, with steric properties of exocyclic substituents having minimal influence on the macrocyclization. Aryl-type endocyclic substituents predominantly yield 6-membered macrocycles, while polycyclic aromatic units such as fluorene and carbazole favor 4-membered species. Experimental and computational studies support a proposed mechanism of ring-walking catalyst transfer that promotes the macrocycle formation. It has been found that the macrocyclization is driven by the formation of cyclic conformers during the oligomerization step favoring an intramolecular C-N bond formation that, depending on the cycle size, hinges on either preorganization effect or kinetic increase of the reductive elimination step or a combination of the two. The CTM process exhibits a living behavior, facilitating sequential synthesis of other macrocycles by introducing relevant monomers, thus providing a practical synthetic platform for chemical libraries. Notably, CTM operates both under diluted and concentrated regimes, offering scalability potential, unlike typical macrocyclization reactions usually operating in the 0.1-1 mM range.
The group is led by Professor Davide Bonifazi at the Institute of Organic Chemistry in the University of Vienna.
We do research in synthetic organic chemistry to develop supramolecular architectures that, through the exploitation of their peculiar physical and structural properties, can contribute to the demonstration of key functions or basic concepts at the intersection of physical organic chemistry, materials science and biology.
One-Step Catalyst-Transfer Macrocyclization: Expanding the Chemical Space of Azaparacyclophanes
On-Surface Molecular Recognition Driven by Chalcogen Bonding
Chalcogen bonding interactions (ChBIs) have been widely employed to create ordered noncovalent assemblies in solids and liquids. Yet, their ability to engineer molecular self-assembly on surfaces has not been demonstrated. Here, we report the first demonstration of on-surface molecular recognition solely governed by ChBIs. Scanning tunneling microscopy and ab initio calculations reveal that a pyrenyl derivative can undergo noncovalent chiral dimerization on the Au(111) surface through double ChN interactions involving Te- or Se-containing chalcogenazolo pyridine motifs. In contrast, reference chalcogenazole counterparts lacking the pyridyl moiety fail to form regular self-assemblies on Au, resulting in disordered assemblies.
Photoredox Annulation of Polycyclic Aromatic Hydrocarbons
The rise of interest in using polycyclic aromatic hydrocarbons (PAHs) and molecular graphenoids in optoelectronics has recently stimulated the growth of modern synthetic methodologies giving access to intramolecular aryl-aryl couplings. Here, we show that a radical-based annulation protocol allows expansion of the planarization approaches to prepare functionalized molecular graphenoids. The enabler of this reaction is peri-xanthenoxanthene, the photocatalyst which undergoes photoinduced single electron transfer with an ortho-oligoarylenyl precursor bearing electron-withdrawing and nucleofuge groups. Dissociative electron transfer enables the formation of persistent aryl radical intermediates, the latter undergoing intramolecular C-C bond formation, allowing the planarization reaction to occur. The reaction conditions are mild and compatible with various electron-withdrawing and -donating substituents on the aryl rings as well as heterocycles and PAHs. The method could be applied to induce double annulation reactions, allowing the synthesis of pi-extended scaffolds with different edge peripheries.
Photoreduction of Anthracenes Catalyzed by peri-Xanthenoxanthene: a Scalable and Sustainable Birch-Type Alternative
The typical Birch reduction transforms arenes into cyclohexa-1,4-dienes by using alkali metals, an alcohol as a proton source, and an amine as solvent. Capitalizing on the strong photoreductive properties of peri-xanthenoxanthene (PXX), herein we report the photocatalyzed Birch-type reduction of acenes by employing visible blue light irradiation at room temperature in the presence of air. Upon excitation at 405 or 460 nm in the presence of a mixture of N,N-diisopropylethylamine (DIPEA) and trifluoromethanesulfonimide (HNTf2) in DMSO, PXX photocatalyzes the selective reduction of full-carbon acene derivatives (24-75 %). Immobilization of PXX onto polydimethylsiloxane (PDMS) beads (PXX-PDMS) allowed the use of the catalyst in heterogeneous batch reactions, giving 9-phenyl-9,10-dihydroanthracene in high yield (68 %). The catalyst could easily be recovered and reused, with no notable drop in performance observed after five reaction cycles. Integration of the PXX-PDMS beads into a microreactor enabled the reduction of acenes under continuous-flow conditions, thereby validating the sustainability and scalability of this heterogeneous-phase approach.
Spinoff Fellowship Demo Day
Congratulations to Laura who presented her IrrevoChrom FFG Spin-off Fellowship topic and spin-off project at the Demo Day in front of the Science Minister Martin Polaschek and the Head of the FFG Henrietta Egerth.
For more info: brutkasten.com/artikel/ffg-spin-off-fellowship-demoday
FFG Spin-off Fellowship awarded
The “IrrevoChrom” project is one out of total eleven recently granted FFG spin-off fellowships that will be led by FFG fellow Laura Maggini and host Davide Bonifazi at the Institute of Organic Chemistry, University of Vienna.
The FFG-funded IrrevoChrom Spin-off Fellowship will build on the patent developed in the Bonifazi group (EP application No EP22164076.6) within the framework of the Charisma Marie-Sklodowska Curie project they are coordinating, entailing the formulation of an irreversible EC matrix composed of both the chromogenic material, an anti-oxidant and electrolyte, to develop and scale-up a commercially viable and completely irreversible electrochromic ink compatible with industrial manufacturing processes.
Upon activation, this ink will provide a stark and permanent color transition (colorless to black), impossible to reverse. Thanks to the new formulations developed in this Fellowship, we will match our technology with industrial ECDs productions processes, jump starting its commercial exploitation, and develop in collaboration with Silicon Austria Labs activatable tamperproof demos.
New DoSChem awardees of “New Ideas” program
DoSChem awards with 24811.20 Euro the joint expertise of Martina Crosta (Institute of Organic Chemistry, Davide Bonifazi group) and David Hernández-Castillo (Institute for Theoretical Chemistry, Leticia González group) with the proposal “Conjugation-Induced TADF Emitters: A Theoretically-Driven Experimental Design”.
Good luck Martina and David with their project!
Best flash talk award for Ruben Ferreira
At the European-Winter School on Physical Organic Chemistry (E-WISPOC 23, www.ewispoc.com) that took place in Bressasone between February 5-10, Rúben Ferreira was awarded with the best flash talk award for his poster with the title “Dynamic Covalent Photowriting“
Congratulations to your prize!
Organization of STiBNite/VIT Summer School: Self-assembled organic materials
Sponsored by two of our on going EU projects, VIT and STiBNite, the summer school took place at the UniVie Skylounge conference room on 4-5 July 2022.
We were delighted to host stimulating lectures both by external speakers and consortia representatives on the topic of self-assembled organic materials.
Big thanks to our wonderful speakers Renaud Nicolay, Francesco Picchioni, Chiara Gualandi, Timothy Swager, Richard Kelly, Laura Maggini, Takuji Hatakeyama, Emilio Perez, Milan Kivala, Susana Otero, Alexander Kros!
For more information about the STiBNite and VIT projects.
These projects have received funding from the European Union’s Horizon 2020 research and innovation programme under the Marie-Sklodowska-Curie grant agreements No 956923 and 101008237.
International Day of Women and Girls in Science
In occasion of the “International Day of Women and Girls in Science”, Bonifazi group @ Institute of Organic Chemistry, UniWien, is organizing IUPAC Global Women’s Breakfast 2022 taking place online on February 16th.
The aim is to celebrate the accomplishments of women in science and to inspire younger generations to pursue careers in science.
The theme for this year is “Empowering Diversity in Science”. The program will include talks from scientists in academia and industry on their personal experiences as women in science. To create mutual connections, there will be a theme quiz and a panel discussion.
You are very welcome to join us on February 16, 08:45 CET with this link.
Click here for the full program: Program-GWB-2022