In one word, how would you describe your research?Dynamic.
How did this research begin?During our work on dynamic processes in Pd/NHC catalytic systems, one of the key techniques we utilized was mass spectrometry.E lectrospray ionization mass spectrometry was applied to understand possible reduction pathways of the studied Pd/NHC complexes. Surprisingly,s everal NHC-free species were detected, unstabilized palladium hydride being one of them. This elusive intermediate caught our attention and we delved into the study of the observed phenomena.What is the most significant result of this study?Formation of palladium complexes, non-stabilized by direct metal bonding with strong NHC ligand, makes av ery important point. Dynamic nature of the catalytic system allows ligand-free ionic palladium complexes to be formed. These ionic species do not agglomerate while being in Pd 0 oxidation state and, notably,t hey can be isolated from the reaction mixture and recycled.
What was the inspiration for this cover design?Thinking about an artwork that might describe dynamic nature of the studied system, we wanted to highlight the ease with which the catalytic system can transform. This brought us to the sketch of palladium complexes on as eesaw.I nt he image we created, alternative palladium complexes play together as friends, seesawed easily up and down by the possibility of dynamic transformations.Invited for the cover of this issue are ValentineP .A nanikov and co-workers. The image depicts the dynamic behaviour of a Pd/NHCc atalytic systemw ith easy transition from molecular to ionic complex. Read the fullt ext of the article at
The first example of an intermolecular thiolyne-ene coupling reaction is reported for the one-pot construction of CÀ S and CÀ C bonds. Thiol-yne-ene coupling opens a new dimension in building molecular complexity to access densely functionalized products. The employment of Eosin Y/DBU/MeOH photocatalytic system suppresses hydrogen atom transfer (HAT) and associative reductant upconversion (via CÀ S threeelectron σ-bond formation). Investigation of the reaction mechanism by combining online ESI-UHRMS, EPR spectroscopy, isotope labeling, determination of quantum yield, cyclic voltammetry, Stern-Volmer measurements and computational modeling revealed a unique photoredox cycle with four radical-involving stages. As a result, previously unavailable products of the thiol-yneene reaction were obtained in good yields with high selectivity. They can serve as stable precursors for synthesizing synthetically demanding activated 1,3-dienes.
The product of a revealed transformation—NHC‐ethynyl coupling—was observed as a catalyst transformation pathway in the Sonogashira cross‐coupling, catalyzed by Pd/NHC complexes. The 2‐ethynylated azolium salt was isolated in individual form and fully characterized, including X‐ray analysis. A number of possible intermediates of this transformation with common formulae (NHC)nPd(C2Ph) (n=1,2) were observed and subjected to collision‐induced dissociation (CID) and infrared multiphoton dissociation (IRMPD) experiments to elucidate their structure. Measured bond dissociation energies (BDEs) and IRMPD spectra were in an excellent agreement with quantum calculations for coupling product π‐complexes with Pd0. Molecular dynamics simulations confirmed the observed multiple CID fragmentation pathways. An unconventional methodology to study catalyst evolution suggests the reported transformation to be considered in the development of new catalytic systems for alkyne functionalization reactions.
This work reveals ambident nucleophilic reactivity of imidazolium cations towards carbonyl compounds at the C2 or C4 carbene centers depending on the steric properties of the substrates and reaction conditions. Such an adaptive
The series of novel Pd/NHCF complexes were synthesized via a straightforward approach from fluorine-containing anilines. Computational and structural studies were performed to assess the effect of fluorine on the Pd–NHC bond.
An efficient strategy
was developed for directing-group-free C–H
functionalization of biomass-derived C6 furanic building
block. Palladium-catalyzed C–H functionalization of the low-reactive
C3 position was successfully performed in 2,5-diformylfuran, an important
derivative of the biobased platform chemical 5-(hydroxymethyl)furfural.
The ligand-free catalytic arylation was carried out without using
protecting or directing groups, which is of key importance for the
studied area to achieve waste-minimized and step-economic biomass
processing. The experimental results combined with density functional
theory calculations revealed a reaction mechanism and indicated that
the presence of the aldehyde group is essential for catalytic reaction.
Enolization of the aldehyde group and Pd binding play an important
role in governing the overall C–H functionalization pathway.
One of the obtained arylated furanic compounds was tested as a model
substrate for reduction and oxidation of carbonyl groups to highlight
its versatile synthetic potential.
An atom-economic ring construction approach to the synthesis of α-(hetero)arylfurans based on renewable furanic platform chemicals has been developed. Corresponding compounds have been prepared in good to excellent yields via [2 + 2 + 2] and [4 + 2] cycloaddition reactions using metal-catalyzed or photoredox protocols. Easily available HMF-based 2-hydroxymethyl-5-ethynylfuran and 2hydroxymethyl-5-cyanofuran were used as starting materials.A synthetic route with an improved carbon economy factor has been implemented to achieve sustainability aim. The possible application of arylfurans as molecular conductors has been investigated by DFT calculations, which revealed excellent charge transfer properties. As a future perspective, integration of biomass processing strategy into manufacturing of molecular electronics was pointed out to achieve the aim of sustainability.
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