Lewis Acid-Assisted C(sp3)–C(sp3) Reductive Elimination at Gold published in the J. Am. Chem. Soc.

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The phosphine-borane iPr2P(o-C6H4)BFxyl2 (Fxyl = 3,5-(F3C)2C6H3) 1-Fxyl was found to promote the reductive elimination of ethane from [AuMe2(μ-Cl)]2. Nuclear magnetic resonance monitoring revealed the intermediate formation of the (1-Fxyl)AuMe2Cl complex. DFT calculations identified a zwitterionic path as the lowest energy profile, with an overall activation barrier more than 10 kcal/mol lower than without borane assistance. The Lewis acid moiety first abstracts the chloride to generate a zwitterionic Au(III) complex, which then readily undergoes C(sp3)–C(sp3) coupling. The chloride is finally transferred back from boron to gold. The electronic features of this Lewis-assisted reductive elimination at gold have been deciphered by intrinsic bond orbital analyses. Sufficient Lewis acidity of boron is required for the ambiphilic ligand to trigger the C(sp3)–C(sp3) coupling, as shown by complementary studies with two other phosphine-boranes, and the addition of chlorides slows down the reductive elimination of ethane.
This paper by Yago García-Rodeja and collaborators can be found in:

https://pubs.acs.org/doi/10.1021/jacs.3c01974

Photoinduced Reactions of C60 and C70 in Water

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Three types of water-soluble fullerene derivatives were prepared from their Prato adducts by conjugation with PEG. One Prato derivative of C60 ([6,6]-addition) and two Prato derivatives of C70 (ab-[6,6] and cc-[6,6]-addition) with carboxylic acids were synthesized, purified and subjected to the amide-forming conjugation with amine-PEG to form corresponding C60– or C70-PEG conjugates. All the conjugates showed photoinduced DNA cleavage by reactive oxygen species (ROS) formed by type II energy transfer pathway or type I electron transfer pathway.

The responsible ROS were measured by ESR spin-trapping methods using 4-oxo-TEMP (for singlet oxygen) and DEPMPO (for superoxide radical anion), and were shown to be significantly different in three materials.  To understand the mechanism of these differences, redox potentials of the precursor molecules were analyzed by cyclic voltammetry in order to determine the difference in electron transfer rates. The lifetimes of the triplet excited states were measured by laser-flash photolysis.  Finally, calculations were performed in the DiMoCat group by Dr. Anton Stasyuk, Prof. Alexander Voityuk and Prof. Miquel Solà to obtain rate constants for each step in the type I and II pathways.

The paper has been highlighted by the Spanish Biophysical Society (https://sbe.es/paperhighlights-oct2021-2/).

The paper can be read in JACS Au journal through the following link:

https://pubs.acs.org/doi/10.1021/jacsau.1c00239

Jesús Antonio Luque Urrutia wins the second prize for the best Spanish computational paper in 2020

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On 19th May 2021, the evaluation committee of the prizes to the best articles produced by Spanish PhD students in the area of Chemistry and Computation in 2020 were announced by the Computation and Chemistry specialized group of the Spanish Royal Society of Chemistry. To our delight, Dr. Jesús Antonio Luque Urrutia, former member of our research group, won the second prize with the paper:

Jesús Antonio Luque-Urrutia, Albert Poater, Miquel Solà
Do carbon nano-onions behave as nanoscopic Faraday cages? A comparison of the reactivity of C60, C240, C60@C240, Li+@C60, Li+@C240, and Li+@C60@C240
Chem. Eur. J., 2020, 26, 804-808
DOI: 10.1002/chem.201904650

Congratulations Xus!

This paper corresponds to the last chapter of the PhD thesis defended by Dr. Luque on 26th March 2021. If you are interested you can see his defense at:

https://www.twitch.tv/videos/1025916063?t=0h0m39s

Sustainable catalysis by Mn: Amide Synthesis from Alcohols and generation of H2 as energy source

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Density functional theory calculations unveil the mechanism of the original example of a base-metal-catalyzed synthesis of amides from alcohols and amines, generating H2 as a subproduct. Instead of a convoluted mechanism with the implication of dissociation of some ligand of the manganese catalyst, our DFT calculations describe a facile protocol, where the catalyst only produces aldehydes from alcohols. Once formaldehyde is formed from methanol, it reacts with the amine to form a second alcohol that undergoes the same procedure as methanol and creates the desired amide through a double-carrousel mechanism. This reaction is eminently sustainable in different ways: it uses alcohols and generates molecular hydrogen, without releasing CO2, but the interesting formation of amides. In addition, to speed up the process the reaction has a manganese catalyst, with manganese being one of the most abundant metals in the Earth’s layer.

A. Luque-Urrutia, T. Pèlachs, M. Solà, A. Poater; “Double-Carrousel Mechanism for Mn-Catalyzed Dehydrogenative Amide Synthesis from Alcohols”; ACS Catal. 2021, DOI: 10.1021/acscatal.1c00693

The Mechanism of the Iodane‐Guided ortho C−H Allylation Unveiled

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This work is the result of a joint collaboration of the DiMoCat group with the groups of with groups of Prof. A. Shafir of the Institute for Advanced Chemistry of Catalonia, Prof. A. B. Cuenca of the Químics de Sarrià, Prof. S. Lethu of the Institute of Chemical Research of Catalonia, and Prof. J. Zhu from Xiamen University. Our group has performed the DFT mechanistic study with a great work by Dandan Chen.

A metal‐free C−H allylation strategy is described to access diverse functionalized ortho‐allyl‐iodoarenes. The method employs hypervalent (diacetoxy)iodoarenes and proceeds through the iodane‐guided “iodonio‐Claisen” allyl transfer. The use of allylsilanes bearing electron‐withdrawing functional groups unlocks the functionalization of a broad range of substrates, including electron‐neutral and electron‐poor rings. The resulting ortho‐allylated iodoarenes are versatile building blocks, with examples of downstream transformation including a concise synthesis of the experimental antimitotic core of Dosabulin. DFT calculations shed additional light on the reaction mechanism, with notable aspects including the aromatic character of the transition‐state structure for the [3,3] sigmatropic rearrangement, as well as the highly stereoconvergent nature of the trans‐product formation.

Chen, W. W.; Cunillera, A.; Chen, D.; Lethu, S.; López de Moragas, A.; Zhu, J. Solà, M.; Cuenca, A. B.; Shafir, A. “Iodane-Guided ortho C-H Allylation” Angew. Chem. Int. Ed. 2020,  DOI: 10.1002/ange.202009369

 

A Review on Mechanistic Studies of Transition-Metal Catalyzed [2+2+2] Cycloaddition Reactions

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The development of catalytic methodologies involving the formation of C-C bonds to enable the generation of cyclic systems constitutes a field of great relevance in synthetic organic chemistry. One paradigmatic process to accomplish this goal efficiently is the transition-metal catalyzed [2+2+2] cycloaddition reaction since it permits the formation of a wide range of highly functionalized six-membered carbo- and heterocyclic molecules in a single step with high efficiency and perfect atom economy. A key feature of these transformations is the mechanistic pathway that they follow, since a deep knowledge of this mechanism may enable us to understand and improve the efficiency of the reaction. This review covers the mechanistic aspects, studied both from theoretical and experimental points of view, of the transition metal-catalyzed [2+2+2] cycloaddition reaction involving all kinds of unsaturated substrates with metals such as Co, Ni, Ru, Rh, Ir, Pd, Zr, Ti, Ta, and Nb. A thorough overview is undertaken, from the seminal studies until the present day, of the key mechanistic aspects that influence the reactivity and selectivity of the reaction, comparing the involvement of different unsaturated substrates as well as the different transition metals used.

The review contains 86 pages, 6684 lines of text, 57971 words, 141 schemes, 9 Figures and 403 references. It has been reviewed by four referees who asked the authors to answer 210 remarks in the first round of peer-review and 46 in the second one. It has been a hard work and a long trip. Congratulations to Anna, Anna, and Miquel!

A. Pla-Quintana*, A. Roglans* and M. Solà*.

Mechanistic studies of transition-metal catalyzed [2+2+2] cycloaddition reactions.

Chem. Rev., 2020, DOI: 10.1021/acs.chemrev.0c00062.