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The synthesis of spiro compounds featuring seven- and six-membered rings in the spirobicyclic motif is successfully achieved through a cascade process encompassing a rhodium(I)-catalyzed cycloisomerization followed by a highly selective Diels-Alder homodimerization. The scope of the reaction is analyzed based on a series of synthetic substrates, and control experiments and DFT calculations led us to justify the exquisite degree of selectivity observed We are grateful for financial support from the Ministerio de Ciencia e Innovación (PID2020-113711GB-I00 MCIN/AEI/ 10.13039/501100011033), the Generalitat de Catalunya (Project 2017-SGR-39), and the UdG for an IF predoctoral grant to J.V. Open Access funding provided thanks to the CRUE-CSIC agreement with ACS

The mechanism for the functionalizaton of 2-alkylpyridine and 2-alkylquinoline derivatives by nitrogen transfer from N2O is unveiled. The reaction is predicted to be feasible for other derivatives featuring N−, O−, and S− heterocycles.

The trapping of the elusive vinylogous position of a vinyl carbene with an aliphatic C(sp3)−H bond has been achieved for the first time during a silver-catalyzed carbene/alkyne metathesis (CAM) process. A Tpx-containing silver complex first promotes the generation of a donor-acceptor silver carbene which triggers CAM, generating a subsequent donor-donor vinyl silver carbene species, which then undergoes a selective vinylogous C(sp3)−H bond insertion, leading to the synthesis of a new family of benzoazepines. Density functional theory (DFT) calculations unveil the reaction mechanism, which allows proposing that the C−H bond insertion reaction takes place in a stepwise manner, with the hydrogen shift being the rate determining step., We are grateful for financial support from the Ministerio de Ciencia e Innovación (PGC2018-097722-B-I00, PID2020113797RB-C21 and PID2020-113711GB-I00 MCIN/AEI/ 10.13039/501100011033 and FPU grants to A.D.-J. and R.M.-C.) and the Generalitat de Catalunya (Project 2017SGR-39). We also thank Junta de Andalucía (P18-1536) and Universidad de Huelva (P.O.Feder UHU202024). A.P.Q. and A.P. are Serra Húnter Fellows and A.P. thanks ICREA Academia Prize 2019. M.A. thanks Junta de Andalucia for a postdoctoral fellowship. E.B. thanks Cátedra Cepsa-Universidad de Huelva for financial support.

A synthetic methodology is reported that functionalizes C60 and C70 fullerenes with dihydroazepine rings by a cascade reaction encompassing a rhodium-catalyzed cycloisomerization of 1,5-bisallenes and a [4+2] cycloaddition. This transition metal-catalyzed cascade reaction provides a versatile and step-economical approach to the synthesis of 6,7-membered polyheterocyclic fullerene adducts. Electrochemical characterization of the products obtained ventures their application in organic and perovskite photovoltaic devices We are grateful for the financial support by the Spanish Ministry of Economy and Competitivity (MINECO) (Projects CTQ2017-85341-P and CTQ2017-83587-P, FPI predoctoral grant to A.A. and C.C.) and the Generalitat de Catalunya (Project 2017-SGR-3 Open Access funding provided thanks to the CRUE-CSIC agreement with Wiley

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 6-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 We gratefully acknowledge the financial support of our own research in this area by the Spanish Ministry of Economy and Competitivity (MINECO) (project CTQ2017-85341-P) and the Generalitat de Catalunya (project 2017-SGR-39, Xarxa de referencia en Química Teórica i Computacional, and ICREA Academia 2014 Award to M.S.)

[2+2+2] Cycloaddition reaction is a captivating process that assembles six-membered rings from three unsaturations with complete atom economy. Of the multiple transition metals that can be used to catalyze this reaction, rhodium offers many advantages. These include high activity and versatility, but especially the ability to easily tune the reactivity and selectivity by the modification of the ligands around the metal. In this personal account, we summarize our endeavours in the development of efficient and sustainable [2+2+2] cycloaddition reactions to prepare products of interest, develop conditions in which the catalyst can be recovered and reused, and understand the mechanistic details that govern the selectivity of the processes This research was funded by the Ministerio de Ciencia e Innovación (projects CTQ2017-85341-P, PID2020-113711GB-I00 MCIN/AEI/10.13039/501100011033) and the Generalitat de Catalunya (Project 2017-SGR-39)

Density functional theory calculations were used to systematically explore the effects of axial ligation by solvent molecules on the reactivity and selectivity of dirhodium tetracarboxylates with diazo compounds in the context of C–H insertion into propane. Insertions on three types of diazo compounds—acceptor/acceptor, donor/acceptor, and donor/donor—promoted by dirhodium tetraformate were tested with and without axial solvent ligation for no surrounding solvent, dichloromethane, isopropanol, and acetonitrile. Magnitudes, origins, and consequences of structural and electronic changes arising from axial ligation were characterized. The results suggest that axial ligation affects barriers for N2 extrusion and C–H insertion, the former to a larger extent.

Density functional theory calculations were used to systematically explore the effects of axial ligation by solvent molecules on the reactivity and selectivity of dirhodium tetracarboxylates with diazo compounds in the context of C–H insertion into propane. Insertions on three types of diazo compounds—acceptor/acceptor, donor/acceptor, and donor/donor—promoted by dirhodium tetraformate were tested with and without axial solvent ligation for no surrounding solvent, dichloromethane, isopropanol, and acetonitrile. Magnitudes, origins, and consequences of structural and electronic changes arising from axial ligation were characterized. The results suggest that axial ligation affects barriers for N2 extrusion and C–H insertion, the former to a larger extent.

Density functional theory calculations were used to systematically explore the effects of axial ligation by solvent molecules on the reactivity and selectivity of dirhodium tetracarboxylates with diazo compounds in the context of C−H insertion into propane. Insertions on three types of diazo compounds - acceptor/acceptor, donor/acceptor, and donor/donor - promoted by dirhodium tetraformate were tested with and without axial solvent ligation for no surrounding solvent, dichloromethane, isopropanol, and acetonitrile. Magnitudes, origins, and consequences of structural and electronic changes arising from axial ligation were characterized. The results suggest that axial ligation affects barriers for N2 extrusion and C−H insertion, the former to a larger extent

A novel methodology to transform C60 into a variety of open-cage fullerene derivatives by employing rhodium(I) catalysis has been developed. This transformation encompasses a partially intermolecular [2+2+2] cycloaddition reaction between diynes 1 and C60 to deliver a cyclohexadiene-fused fullerene, which concomitantly undergoes a formal [4+4]/retro-[2+2+2] rearrangement to deliver open-cage fullerenes 2. Most notably, this process occurs without the need of photoexcitation. The complete mechanism of this transformation has been rationalized by DFT calculations, which indicate that, after [2+2+2] cycloaddition, the cyclohexadiene-fused intermediate evolves into the final product through a Rh-catalyzed di-π-methane rearrangement followed by a retro-[2+2+2] cycloaddition. The obtained open-cage fullerenes can be derivatized by Suzuki-Miyaura cross-coupling or subjected to ring expansion to deliver a 12-membered ring orifice in the fullerene structure. Overall, the methodology presented constitutes a straightforward entry to functional open-cage C60 fullerene derivatives by employing catalytic methods.

Open-cage fullerenes, fullerenes with orifices created by breaking some of the C-C bonds in a fullerene such as C60, are molecules that allow chemical access to both the external and the internal surfaces of the carbon cage. We have found such molecules to be challenging to crystallize and thereby fully structurally characterize through single crystal X-ray diffraction studies. We have also found that the reactivity of these open cage fullerenes can differ significantly from that of the parent fullerene (see A. Aghabali, S. Jun, M. M. Olmstead, A. L. Balch, Silver(I)-Mediated Modification, Dimerization, and Polymerization of an Open-Cage Fullerene. J. Am. Chem. Soc. 2016, 138, 16459-16465.) This talk will report recent studies of the crystallographically determined structures and reactivities of several open-cage fullerenes with particular attention given to the accessibility of the cage opening to chemical reactions.

N-Tosylhydrazone-yne-ene substrates are satisfactorily prepared and their cyclization under rhodium catalysis is evaluated. A cascade process involving rhodium vinyl carbene formation – through carbene/alkyne metathesis – and cyclopropanation has been developed to stereoselectively afford vinylcyclopropanes We are grateful for the financial support by the Spanish Ministry of Education and Science (MINECO) (Project CTQ2014-54306-P) and the DIUE of the Generalitat de Catalunya (Project 2014-SGR-931 and FI predoctoral grant to >.T.)

The electronic and steric factors that favour the formation of 1,2,4- and 1,3,5-regioisomers in the intermolecular [2+2+2] cyclotrimerisation of terminal alkynes are not well understood. In this work, this problem was analysed from a theoretical and experimental point of view. Density functional theory (DFT) calculations of the [2+2+2] cyclotrimerisation of p-X-substituted phenylacetylenes (X = H, NO2, and NH2) catalysed by [Rh(BIPHEP)]+ were carried out to determine the reaction mechanism in each case and analyse the effect that the electronic character of the substituents has on the regioselectivity. For the rate-determining step corresponding to the oxidative coupling leading to the rhodacyclopentadiene intermediate, we have taken into account two reaction pathways: the reaction pathway with the lowest energy barrier and the reaction pathway through the most stable transition state (Curtin-Hammett pathway). Our results show that the theoretical results conform experimental outcomes for different p-X-substituted phenylacetylenes (X = NO2, F, H, Me, tBu, OMe, NMe2) only when the Curtin-Hammett reaction pathway is considered. A fairly good correlation has been obtained between the electronic nature of the substituents (as expressed by the Hammett σpara constant values) and the regioisomeric ratios experimentally obtained and computationally predicted Financial support from the Spanish Ministry of Economy and Competitivity (MINECO) (Project No. CTQ2017-85341-P) and the DIUE of the Generalitat de Catalunya (Project No. 2017SGR39 and ICREA Academia 2014 to M. S.) are acknowledged. Thanks are due to the Generalitat de Catalunya for FI predoctoral grants to Ò.T., M.F. and À.D.-J. The EU under the FEDER grant UNGI10-4E-801 has also funded this research

The synthesis, characterization, and incorporation of open-cage [60]fullerene derivatives as electron-transporting materials (ETMs) in perovskite solar cells (PSCs) with an inverted planar (p-i-n) structure is reported. Following optical and electrochemical characterization of the open-cage fullerenes 2a–c, p-i-n PSCs with a indium tin oxide (ITO)/poly(3,4-ethylenedioxythiophene)-polystyrene sulfonate (PEDOT:PSS)/perovskite/fullerene/Ag structure were prepared. The devices obtained from 2a–b exhibit competitive power conversion efficiencies (PCEs) and improved open-circuit voltage (Voc) values (>1.0 V) in comparison to a reference cell based on phenyl-C61-butyric-acid methyl-ester (PC61BM). These results are rationalized in terms of a) the higher passivation ability of the open-cage fullerenes with respect to the other fullerenes, and b) a good overlap between the highest occupied molecular orbital/lowest unoccupied molecular orbital (HOMO/LUMO) levels of 2a–b and the conduction band of the perovskite.

A novel methodology to transform C

A RhI/(S)-BINAP catalytic system is able to promote carbene alkyne metathesis and cascade this elemental step with an stereoselective reaction with allenes. An unusual carbene/allene reactivity is discovered that, through a formal addition of p-toluenesulfinic acid to a Rh-bound trimethylenemethane intermediate, affords 4-methylenetetrahydropyran compounds in good yields and excellent enantioselectivities We are grateful for the financial support by the Spanish Ministry of Economy and Competitiveness (MINECO) (Project CTQ2014-54306-P) and the Generalitat de Catalunya (Project 2014-SGR-931, Xarxa de Referència en Química Teòrica i Computacional, ICREA Academia 2014 prize for M. S., and FI predoctoral grant to O.T.). The EU under the FEDER grant UNGI10-4E-801 has also funded this research

The functionalization of fullerenes helps to modulate their electronic and physicochemical properties, generating fullerene derivatives with promising features for practical applications. Herein, DFT is used to explore the attachment of a cyclohexadiene ring to C

Financial support from the Spanish Ministerio de Ciencia e Innovacion (MICINN) (grant numbers CTQ2011-23121, CTQ2009-07881, CTQ2012-32436, CTQ2011-22649, CSD2007-00006) and by the Generalitat de Catalunya (grant numbers 2009SGR637, 2009SGR1441, and predoctoral grant to M. Fernandez) is acknowledged. M. Ferre thanks the Universitat Autonoma de Barcelona for a predoctoral scholarship

Allene-ene-allene (2 and 5) and allene-yne-allene (3 and 7) N-tosyl and O-linked substrates were satisfactorily synthesised. The [2+2+2] cycloaddition reaction catalysed by the Wilkinson catalyst [RhCl(PPh3)3] was evaluated. Substrates 2 and 5, which bear a double bond in the central position, gave a tricyclic structure in a reaction in which four contiguous stereogenic centres were formed as a single diastereomer. The reaction of substrates 3 and 7, which bear a triple bond in the central position, gave a tricyclic structure with a cyclohexenic ring core, again in a diastereoselective manner. All cycloadducts were formed by a regioselective reaction of the inner allene double bond and, therefore, feature an exocyclic diene motif. A Diels-Alder reaction on N-tosyl linked cycloadducts 8 and 10 allowed pentacyclic scaffolds to be diastereoselectively constructed. The reactivity of the allenes on [2+2+2] cycloaddition reactions was studied for the first time by density functional theory calculations. This mechanistic study rationalizes the order in which the unsaturations take part in the catalytic cycle, the reactivity of the two double bonds of the allene towards the [2+2+2] cycloaddition reaction, and the diastereoselectivity of the reaction S'ha preparat satisfactòriament compostos contenint dues unitats d'allé i un doble (2 i 5) o un triple enllaç (3 i 7) amb unitats enllaçants N-tosil i O. Aquests compostos s'han emprat com a substrats en processos de cicloaddicio [2+2+2] catalitzats pel complex de Wilkinson [RhCl(PPh3)(3)]. Els substrats 2 i 5, contenint un doble enllac en posicio central, han donat compostos triciclics en una reaccio on s'han format de forma diastereoselectiva quatre centres estereogenics. La reaccio dels substrats 3 i 7 contenint un triple enllac en posicio central, han permes lobtencio de tricicles contenint un anell central ciclohexanic en una reaccio de nou diastereoselectiva. Tots els cicloadductes s'han format mitjancant la reaccio regioselectiva del doble enllac intern de lalle. Aixi s'han obtingut compostos contenint un die exociclic. Una reaccio de Diels-Alder en els substrats amb unio N-tosil 8 i 10, ha permes la construccio diastereoselectiva destructures pentacicliques. La reactivitat dels allens en la cicloaddicio [2+2+2] s'ha estudiat per primer cop mitjancant calculs terics basats en la teoria del funcional de la densitat. Aquest estudi mecanistic ha permes racionalitzar lordre en que les insaturacions participen en la reaccio, la reactivitat dels dos dobles enllacos de lalle en la cicloaddicio [2+2+2] i la diastereoselectivitat del proces Financial support from the Spanish Ministry of Education and Science (MINECO) (projects nos.: CTQ2011-23121/BQU, CTQ2011-23156/BQU and CTQ2012-32436), the DIUE of the Generalitat de Catalunya (project no.: 2009SGR637), and the FEDER fund (European Fund for Regional Development) for the grant UNGI08-4E-003 is gratefully acknowledged. E. H. thanks Universitat de Girona for a predoctoral grant. Excellent service by the Centre de Serveis Cientifics i Academics de Catalunya (CESCA) is gratefully acknowledged. Support for the research of M. S. was received through the ICREA Academia 2009 prize for excellence in research funded by the DIUE of the Generalitat de Catalunya

An efficient method for the synthesis of N-arylated pyridazinones from potassium 2-furantrifluoroborate and aryldiazonium salts is described. The reaction was run in water at 0-5 °C in short reaction times and without any catalyst or additive. A mechanistic proposal is made based on the experimental data and DFT calculations We thank MINECO (Projects CTQ2011-23121, 23156, and CTQ2012-32436) and the Generalitat de Catalunya (Project 2009SGR637, ICREA Academia for M.S.) for financial support

Aryl-heteroaryl and heteroaryl-heteroaryl compounds are obtained through the Suzuki-Miyaura cross-coupling reactions between diazonium salts and potassium trifluoroborates using PdCl2(CH3CN)2 as the catalyst in water and in the absence of any additive, ligand or base. In addition, the same mild catalytic system is effective for the Matsuda-Heck reaction between several monoolefins with aryldiazonium salts Financial support from MICINN (CTQ2011-23121) of Spain and 'Generalitat de Catalunya' (2009SGR637) is acknowledged

The synthesis of three new families of dendrimeric compounds possessing two different types of functions is reported. These functions are triethoxysilyl group(s), potentially suitable for grafting onto materials, in particular silica, and primary amines (in their protected form), potentially suitable for trapping CO2. All these dendrimeric compounds are based on phosphorus dendrimers, and possess either one Si(OEt)3 group at the core of dendrons or of “off-centre” dendrimers, or several Si(OEt)3 groups precisely placed on half of the terminal groups. These compounds are characterized by 31P NMR spectroscopy, which affords precious information on the structure, confirmed, in one case, by the X-ray diffraction structure of a first-generation dendrimer.

The functionalization of fullerenes helps to modulate their electronic and physicochemical properties, generating fullerene derivatives with promising features for practical applications. Herein, DFT is used to explore the attachment of a cyclohexadiene ring to C60 through a rhodium-catalyzed intermolecular [2+2+2] cycloaddition of C60 and acetylene. All potential reaction paths are analyzed and it can be concluded that the [2+2+2] cycloaddition of C60 and two acetylene molecules catalyzed by [RhCl(PPh3)3], yielding a cyclohexadiene ring fused to a [6,6] bond of C60, is energetically feasible Funded by: Ministerio de Economía y Competitividad. Grant Number: CTQ2014-54306-P; Ministerio de Economia y Competitividad (MINECO). Grant Number: RYC2012-11112 Generalitat de Catalunya. Grant Numbers: 2014SGR931, ICREA Academia 2014 European Union. Grant Number: UNGI10-4E-801

A rhodium-catalyzed asymmetric synthesis of 5,5-disubstituted cyclohexa-1,3-dienes has been achieved by [2+2+2] cycloaddition reactions between diynes and Morita-Baylis-Hillman (M-B-H) adducts as unsaturated substrates. Products containing two adjacent chiral centres (quaternary and tertiary, respectively) were obtained with complete diastereoselectivity and high enantioselectivity (84-97%) through a kinetic resolution of the M-B-H adduct. Furthermore, these highly substituted cyclohexadienes reacted with dienophiles to afford the corresponding Diels-Alder cycloadducts in good yields

Transition metal carbenes are versatile intermediates that can mediate many reactions. Among the different reactions they can participate in, their reactions with alkynes are especially diverse. The present digest describes the different reaction pathways that can take place when a transition metal carbene reacts with an alkyne, summarizes the most recent developments for each reactivity profile, and tries to shed light on the factors influencing the different reaction types

The combination of cationic rhodium(I) complexes with N-phosphino tert-butylsulfinamides (PNSO) ligands is efficient for catalytic intra- and intermolecular [2+2+2] cycloaddition reactions. PNSO ligands are a new class of chiral bidentate ligands, which have the characteristic of combining the easily accessible sulfur chirality with the coordinating capacity of phosphorous. Cycloaddition of open-chained and macrocyclic E-enediynes with these chiral complexes have proved to be highly efficient in terms of yields, giving moderate enantiomeric excesses of the corresponding cyclohexadiene derivatives. In addition Rh(I)/PNSO complexes catalyzed the intermolecular cycloaddition of diynes with monoalkynes in mild reaction conditions and short reaction times.

Rhodium(I)-catalyzed [2+2+2] cycloaddition reactions of N-tosyl-, carbon-, and oxygen-tethered cyanodiynes in a completely intramolecular fashion have been optimized to afford highly functionalized pyridines by conventional and/or microwave heating. Microwaves have been shown to enhance the process by allowing the reaction to be conducted effectively in short reaction times. The methodology has been extended for the synthesis of bipyridines, either by treating a cyanodiyne with an appended pyridine or by conducting a double [2+2+2] cycloaddition reaction on a dicyanotetrayne scaffold. The choice of the solvent in the microwave heating reaction has been shown to be crucial for the success of the process.

In the last decade, a major effort has been devoted to theachievement of efficient organic materials for nonlinearoptics (NLO). Optimization has been sought at both themolecularandthesupramolecularlevel.Ofmajorimportanceis the awareness that the NLO properties of organic-basedmaterials can be different from the sum of the properties ofthe isolated molecules.

Rhodium complexes of N-heterocyclic carbenes (NHC) [RhCl(cod)(NHC)], [cod=1,5-cyclooctadiene, NHC = 1,3-diisopropylimidazolin-2-ylidene, and NHC = 1,3-dimesitylimidazolin-2-ylidene] are tested for intra- and partially intramolecular [2+2+2]-cycloaddition reactions demonstrating their effectiveness in this kind of process. This is the first use of a rhodium-NHC complex in a [2+2+2]-cycloaddition reaction of three alkynes. ESI-MS has been used to detect oxidative addition intermediates using rhodium NHC as the catalytic system.

The IR spectra of P(1) phosphorus dendrimer built from an octasubstituted metal-free phthalocyanine core have been recorded in the region 4000-400cm(-1). Besides the phthalocyanine core, P(1) possess also eight C(6)H(4)-CHN-N(CH(3))-P(S) arms and terminal P-Cl groups. The optimized molecular geometry, frequency and intensity of the IR bands have been calculated using density functional theory (DFT). The P(1) molecules exist in a stable conformation with planar C(6)H(4)-CHN-N(CH(3))- fragments and phthalocyanine core. The calculated geometrical parameters and harmonic vibrational frequencies are predicted in a good agreement with the experimental data. The experimental IR spectrum of P(1) dendrimer was interpreted by means of potential energy distributions. Relying on DFT calculations a complete vibrational assignment is proposed. The difference IR spectra of molecules built from the thiophosphoryl, cyclotriphosphazene, and phthalocyanine cores with the same repeated units and terminal groups were studied in order to undermine the role of the core functionality on the dendrimer architecture.

Two palladium complexes containing triene-coordinated ligands, 3 and 4, open-chain analogues of the macrocyclic palladium(0) complexes of type 1, have been synthesized. A comparative study of both open-chain and macrocyclic complexes has been carried out, based on a NMR and X-ray structural analysis, a DSC thermal behavior assessment, and a catalytical activity evaluation in the arenediazonium and organotrifluoroborate cross-coupling Suzuki−Miyaura reaction. The 1,6,11-triene sequence has been revealed to be crucial in the great stability of this family of palladium(0) complexes.

Two synthetic routes to "Janus"-type dendrimers possessing ammonium groups on one side and fluorescent dansyl derivatives on the other side are described. These surface-block dendrimers are obtained by the coupling of two different dendrons, built from the hexafunctional cyclotriphosphazene core. Their characterization and their photophysical behavior are reported. The largest compound possesses 10 ammonium groups and 5 dansyl groups; it is potentially useful as a fluorescent label in materials science and biology.

The reaction of diyne arylsulfonyl hydrazone substrates under rhodium(I)/BINAP catalysis gives access to sulfonated azacyclic frameworks in a highly enantioselective manner. This new cascade process considerably increases the molecular complexity by generating two C-C bonds, one C-S bond, and one C-H bond. Theoretical calculations, competitive experiments, and deuterium labeling have jointly been used to propose a mechanism that accounts for the reaction. The mechanism involves the formation of vinyl rhodium carbenoids, hydride migratory insertion, and intermolecular stereoselective nucleophilic attack. The last two steps are the key to the stereoselectivity of the process.

The complexation of a first-generation dendrimer possessing a metal-free octasubstituted phthalocyanine as its core has been carried out with copper and cobalt chlorides. In the case of the cobalt complex, the synthesis of the dendrimer has been pursued up to the eighth generation. The progressive influence of the branches upon the core has been studied

Selective and efficient preparation of a new chiral dipalladium(0) complex with an olefinic macrocyclic ligand named (E,E,E,E,E,E)-1,6,11,16,21,26-hexakis[(4-methylphenyl)sulfonyl]-1,6,11,16,21,26-hexaazacyclotriaconta-3,8,13,18,23,28-hexaenedipalladium(0) (5) is reported. Dinuclear palladium(0) complex 5 has been fully characterized by means of NMR spectroscopy and X-ray diffraction analysis.

A rhodium-catalyzed [2 + 2 + 2] cycloaddition of cyano-yne-allene scaffolds followed by a dehydrogenative process enabling the direct synthesis of unsaturated pyridine-containing compounds that can be conveniently converted to 2,6-naphthyridine derivatives is reported.

Financial support from the Spanish Ministerio de Ciencia e Innovacion (MICINN) (grant numbers CTQ2011-23121, CTQ2009-07881, CTQ2012-32436, CTQ2011-22649, CSD2007-00006) and by the Generalitat de Catalunya (grant numbers 2009SGR637, 2009SGR1441, and predoctoral grant to M. Fernandez) is acknowledged. M. Ferre thanks the Universitat Autonoma de Barcelona for a predoctoral scholarship

A novel type of chiral and stable palladium(0) complexes of polyunsaturated aza-macrocyclic ligands were prepared and fully characterized by means of NMR spectroscopy and X-ray diffraction. Fifteen-membered alkene−alkyne type ligands as well as 20- and 25-membered polyolefinic ligands showed a preference for tricoordination with the metal. The stereochemical complexity of these complexes is related to the different isomers that can be formed by complexation of the metal to either of the two faces of each of the olefins involved. The palladacyclopropane formulation of the palladium−olefin interaction offers a clear picture of the stereogenicity of the olefin carbon atoms when they are coordinated to the metal. The preorientation of the macrocyclic ligand and the prepositioning of the olefinic bonds for complex formation facilitated by six-membered chelate rings explain the stability of the structures. The conformation of the palladacyclohexanic rings is found to be crucial in the stereoisomers formed. Thes...

A stepwise preparation of a series of nitrogen-containing 25-membered pentaolefinic macrocycles is presented. The corresponding arenesulfonamides and trans-1,4-dibromo-2-butene served as precursors for the synthesis.

Allylic substitution of PhCH(OAc)CHCHPh by CH2(COMe)2 in a basic MeOH/H2O mixture could be achieved in the absence of a palladium catalyst and lead to a mixture of PhCH(CH(COMe)2)CHCHPh and PhCH(OMe)CHCHPh in 40% and 55% yields, respectively. The process is induced by water, and nucleophilic attack addition occurred on a stabilized carbocation as the intermediate. Addition of a catalytic amount of PdCl2(CH3CN)2 did not accelerate the reaction but improved the selectivity, and PhCH(CH(COMe)2)CHCHPh was then obtained in 92% yield while PhCH(OMe)CHCHPh was observed in trace amounts. An ESI-MS analysis of the reaction mixture led us to assume that a palladium acetylacetonate complex is involved in the formation of PhCH(CH(COMe)2)CHCHPh.