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Fast and efficient galvanostatic conversion of 2,4-diarylfurans into dimeric furan-2(5 H )-ones is now possible in one pot and good yields at room temperature in sustainable aqueous organic solvent. Recent applications of these highly desired structures demand our attention since they are a versatile alternative to acrylates in polymerization to achieve green materials. The reaction mechanism proposal, supported by density functional theory (DFT) theoretical calculations, involves furanoxy radicals, detected by electron paramagnetic resonance (EPR), as the last intermediate before a homocoupling step that affords butenolides. The process can be successfully extended to an array of electron-donating and electron-withdrawing substituents on the aromatic ring. The proposed pathways to explain the formation of the products are rationalized and discussed. A concomitant oxidation of water to hydroxyl radicals is not discarded, particularly with electron-withdrawing substituents at the aromatic ring. In addition, the biological activity as biocides of the obtained compounds was tested, and they showed promising activity against Staphylococcus aureus ., Competing Interests: The authors declare no competing interest., (© 2024 The Author(s).)

We have synthesised and characterised the complex Ni(tpy) 2 (tpy = 2,2':6',2''-terpyridine). This formally Ni(0) complex is paramagnetic both in the solid state and in solution ( S = 2). The crystal structure shows an octahedral geometry, with molecules arranged in independent dimers involving π-stacking between pairs of complexes. Magnetic measurementes and DFT calculations suggest the existence of temperature-dependent intermolecular antiferromagnetic coupling in the solid state.

Cyclobutane-fused dihydropyridones can be efficiently synthesized by a completely endo -selective gold-catalyzed cyclization of alkynylcyclobutanes bearing an appended amide, which proceeds under mild conditions. The observed selectivity, which is reversed from that previously observed for the cyclization of related alcohols and acids, is supported by DFT calculations.

A synthesis of skipped 1,4-enynes through functionalization of the cyclobutene core with alkynes has been achieved, suggesting an unusual pathway of oxidative addition in tertiary iodoalkanes.

The formation of catalytically active alkyl-Ni(i) complexes by comproportionation of diorgano-Ni(ii) precursors and Ni(0) species proceeds easily through triplet states by alkyl ligand exchange. The process involves inversion of the configuration at the carbon that is transferred.

New (triflyl)cyclobutenes have been prepared by palladium-catalyzed hydrodetriflylation reaction using water and deuterium oxide as convenient hydrogen and deuterium sources. In addition, an investigation of the possible mechanism for this Tsuji-Trost type reaction of bis(triflyl)cyclobutenes has been facilitated by labelling studies and density functional theory (DFT) calculations.

We report a novel atom-economical Ni-catalyzed cyclization reaction of enynes with alkynylboronates. The reaction employs a non-expensive Ni salt, a phosphine-based ligand and easy-handling alkynylboronates as boron-carbon source. The reaction provides complex fused-bicyclic compounds containing borylated 1,4-cyclohexadienes in high yields in short reaction times, involving the formation of two C-C bonds in one step. A reasonable reaction mechanism is proposed based on mechanistic experimental results., (© 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Olefins devoid of directing or activating groups have been dicarbofunctionalized here with two electrophilic carbon sources under reductive conditions. Simultaneous formation of one C(sp 3 )-C(sp 3 ) and one C(sp 3 )-C(sp 2 ) bond across a variety of unbiased π-systems proceeds with exquisite selectivity by the combination of a Ni catalyst with TDAE as sacrificial reductant. Control experiments and computational studies revealed the feasibility of a radical-based mechanism involving, formally, two interconnected Ni(I)/Ni(III) processes and demonstrated the different ability of Ni(I) species (Ni(I)I vs PhNi(I)) to reduce the C(sp 3 )-I bond. The role of the reductant was also investigated in depth, suggesting that a one-electron reduction of Ni(II) species to Ni(I) is thermodynamically favored. Further, the preferential activation of alkyl vs aryl halides by ArNi(I) complexes as well as the high affinity of ArNi(II) for secondary over tertiary C-centered radicals explains the lack of undesired homo- and direct coupling products (Ar-Ar, Ar-Alk) in these transformations.

We report a Ni-catalyzed diborylative cyclization of enynes that affords carbo- and heterocycles containing both alkyl- and alkenylboronates. The reaction is fully atom-economical, shows a broad scope, and employs a powerful and inexpensive catalytic Ni-based system. The reaction mechanism seems to involve activation of the enyne by Ni(0) through oxidative cyclometalation of the enyne prior to diboron reagent activation. An unprecedented dinuclear bis(organometallic) Ni(I) intermediate complex was isolated.

We have performed a systematic study of the electron structure of a series of Ni(I) and Ni(II) iodo and methyl complexes with a variety of di- and tridentate nitrogen ligands to study the influence of these ligands in the structure of catalytically active complexes in cross-coupling reactions. Ni(II) compounds show the expected square-planar configuration typical of complexes of d 8 metals, regardless of the kind of coordinating nitrogen atom (sp 2 or sp 3 ) found in ligands derived from either trialkylamines or pyridines. In contrast, Ni(I) complexes show different structures. Thus, the absence of orbitals capable of delocalizing the unpaired electron (such as in TMEDA and PMDTA derivatives) leads to nonplanar iodo or methyl tetracoordinate complexes. In contrast, the presence of ligands derived from pyridine allows delocalization of the unpaired electron on the ligand. This delocalization is especially effective for terpyridine species.

An unprecedented Pt-catalysed cyclisation of N-tethered 1,5-bisallenes in the presence of oxygen nucleophiles is reported, where formation of 6- or 7-membered rings is driven by the choice of nucleophile and the mechanism dictated by the nucleophile and the electronic properties of the bisallene. The reaction in the presence of alcohols gives preferentially vinyltetrahydropyridines with an extra alkoxy group and Pt-H as the active species in the catalytic cycle, while formation of di- and tetrahydroazepines with an extra hydroxyl group is favoured when water is used as nucleophile, via nucleophilic attack/carbocyclization as the favoured pathway. The products obtained are frequently found in the core of natural products with important biological activities, so understanding this complex mechanistic behaviour and exploiting this new methodology will have a big impact in organic synthesis and organometallic chemistry.

This detailed protocol describes the new Spin Saturation Transfer Difference Nuclear Magnetic Resonance protocol (SSTD NMR), recently developed in our group to study processes of mutual-site chemical exchange that are difficult to analyze by traditional methods. As the name suggests, this method combines the Spin Saturation Transfer method used for small molecules, with the Saturation Transfer Difference (STD) NMR method employed for the study of protein-ligand interactions, by measuring transient spin saturation transfer along increasing saturation times (build-up curves) in small organic and organometallic molecules undergoing chemical exchange. Advantages of this method over existing ones are: there is no need to reach coalescence of the exchanging signals; the method can be applied as long as one signal of the exchanging sites is isolated; there is no need to measure T1 or reach steady state saturation; rate constant values are measured directly, and T1 values are obtained in the same experiment, using only one set of experiments. To test the method, we have studied the dynamics of the hindered rotation of N,N-dimethylamides, for which much data is available for comparison. The thermodynamic parameters obtained using SSTD are very similar to the reported ones (spin-saturation transfer techniques and line-shape analysis). The method can be applied to more challenging substrates that cannot be studied by previous methods. We envisage that the simple experimental set up and the wide applicability of the method to a great variety of substrates will make this a common technique amongst organic and organometallic chemists without extensive expertise in NMR.

Controlled preparation of 2,5-dihydro-1H-pyrroles, 3,6-dihydro-2H-pyrans, and pyrroles has been achieved through switchable chemo- and regioselectivity in the metal-catalyzed heterocyclization reactions of allenic amino alcohols. The gold-catalyzed cycloisomerization reaction of α-amino-β-hydroxyallenes was effective as 5-endo cyclization by addition of amino functionality to the distal allene carbon to yield enantiopure 2,5-dihydro-1H-pyrroles, whereas their palladium-catalyzed cyclizative coupling reactions furnished 3,6-dihydro-2H-pyrans through a chemo- and regioselective 6-endo cycloetherification. Conversely, the gold-catalyzed heterocyclization reaction of β-amino-γ-hydroxyallenes generated exclusively pyrrole derivatives. These results could be explained through a chemo- and regioselective 5-exo aminocyclization to the central allene carbon followed by aromatization. Chemo- and regioselectivity depend on both linker elongation as well as the type of catalyst. This behavior can be justified by means of density functional theory calculations.

We report here the Initial Growth Rates SSTD NMR method, as a new powerful tool to obtain the kinetic parameters of intramolecular chemical exchange in challenging small organic and organometallic molecules.

A straightforward metal-mediated method for the synthesis of bis(dihydrofuryl) cyclophane scaffolds from carbonyl compounds has been developed. The combination of the dihydrofuran moiety with different heterocycles such as β-lactams and sugars allows high levels of skeletal diversity. The process comprises indium-promoted one-pot carbonyl bis(allenylation) and gold- or palladium-catalyzed double cyclization in the resulting bis(allenols), followed by selective ruthenium-catalyzed macrocyclization. In some cases, the method has been successfully applied to the synthesis of the challenging Z-isomers. The E- versus Z-stereochemistry of the metathesis-formed double bonds could not be assigned taking into consideration the usual coupling constants criteria, but a diagnostic based on the chemical shifts of the two olefinic protons located at the macrocyclic double bond was established.

The gold-acid-co-catalyzed synthesis of nine series of fused azaheterocycles with structural diversity starting from the same synthons as readily available propargylic hydroperoxides and aromatic amines has been achieved. The overall tandem process consists in a gold-catalyzed hydroperoxide rearrangement/Michael reaction followed by a final acid-catalyzed cyclization., (© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Starting from β,γ-allendiols and α-allenic acetates, a chemo- and regiocontrolled palladium-catalyzed methodology has provided access to enantiopure 3,6-dihydropyrans that bear a buta-1,3-dienyl moiety. Thus, it has been demonstrated for the first time that the preparation of six-membered heterocycles through cross-coupling reactions of two different allenes can be accomplished. These heterocyclization/cross-coupling reactions have been developed experimentally and their mechanisms have additionally been investigated by a computational study., (Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

A combined experimental and computational study on regioselective gold-catalyzed synthetic routes to 1,3-oxazinan-2-ones (kinetically controlled products) and 1,3-oxazin-2-one derivatives (thermodynamically favored) from easily accessible allenic carbamates has been carried out.

Controlled gold-catalyzed reactions of primary and secondary propargylic hydroperoxides with a variety of nucleophiles including alcohols, phenols, 2-hydroxynaphthalene-1,4-dione, and indoles allow the direct and efficient synthesis of β-functionalized ketones. Moreover, the utility of some of the resulting products for the selective preparation of fused polycycles has been demonstrated. In addition, density functional theory (DFT) calculations and (18)O-labeling experiments were performed to obtain an insight into various aspects of the controlled reactivity of propargylic hydroperoxides with external nucleophiles under gold catalysis.

First insights into the reaction between a Baylis-Hillman adduct and an allene moiety have been obtained from the novel domino heterocyclization/cross-coupling reaction of alpha-allenols and Baylis-Hillman acetates, which furnishes [(2,5-dihydrofuran-3-yl)methyl]acrylate derivatives in moderate to good yields.