News @ Views article in Nature Synthesis

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A paper in the News & Views section of Nature Synthesis reporting the significance of Rh-catalyzed cycloaddition reactions done by Uchiyama, Tanaka and co-workers has been written by Anna Roglans and Anna Pla-Quintana.

Dr. Roglans and Dr. Pla-Quintana take advantage of their expertise in transition-metal catalysed [2+2+2] cycloaddition reactions of unsaturated substrates to summarise and highlight the work done by this Japanese research group. We note that this process is a powerful tool to synthesize a wide range of six-membered rings with high levels of diversity and complexity in a single reaction step with perfect atom economy.

Pla-Quintana, A., Roglans, A. Cyclotrimerization takes orders from rhodium. Nat. Synth (2022). https://doi.org/10.1038/s44160-022-00059-8.

 

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 adaptive aromaticity of metallapentalenes in the Front Cover of Chem. Eur. J.!

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The Chemistry: A European Journal features in its FRONT COVER of issue number 57 of volume 26 the recently published article “Proving the origin of adaptive aromaticity in 16-valence-electron metallapentalenes”. The work has been carried out by Prof. Jun Zhu at the University of Xiamen and Dandan Chen, Dr. Dariusz W. Szczepanik, and Prof. Miquel Solà members of the DiMoCat group of the Institute of Computational Chemistry and Catalysis of the University of Girona. The cover is the result of the artistic inspiration of Dandan Chen. The paper has been highlighted in Chem. Eur. J. 26 (2020) 12902

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.