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The serotonin type 6 receptor (5-HT 6 R) displays a strong constitutive activity, suggesting it participates largely in the physiological and pathological processes controlled by the receptor. The active states of 5-HT 6 R engage particular signal transduction pathways that lead to different biological responses. In this study, we present the development of 5-HT 6 R neutral antagonists at Gs signaling built upon the 2-phenylpyrrole scaffold. Using molecular dynamics simulations, we outline the relationship between the exposure of the basic center of the molecules and their ability to target the agonist-activated state of the receptor. Our study identifies compound 30 as a potent and selective neutral antagonist at 5-HT 6 R-operated Gs signaling. Furthermore, we demonstrate the cytoprotective effects of 30 and structurally diverse 5-HT 6 R neutral antagonists at Gs signaling in C8-D1A cells and human astrocytes exposed to rotenone. This effect is not observed for 5-HT 6 R agonists or inverse agonists. In light of these findings, we propose compound 30 as a valuable molecular probe to study the biological effects associated with the agonist-activated state of 5-HT 6 R and provide insight into the glioprotective properties of 5-HT 6 R neutral antagonists at Gs signaling., Competing Interests: Declaration of competing interest All authors disclose no financial or personal relationships that may be perceived as influencing their work., (Copyright © 2024 The Authors. Published by Elsevier Masson SAS.. All rights reserved.)

The multifactorial origin and neurochemistry of Alzheimer's disease (AD) call for the development of multitarget treatment strategies. We report a first-in-class triple acting compound that targets serotonin type 6 and 3 receptors (5-HT-Rs) and monoamine oxidase type B (MAO-B) as an approach for treating AD. The key structural features required for MAO-B inhibition and 5-HT 6 R antagonism and interaction with 5-HT 3 R were determined using molecular dynamic simulations and cryo-electron microscopy, respectively. Bioavailable PZ-1922 reversed scopolamine-induced cognitive deficits in the novel object recognition test. Furthermore, it displayed superior pro-cognitive properties compared to intepirdine (a 5-HT 6 R antagonist) in the AD model, which involved intracerebroventricular injection of an oligomeric solution of amyloid-β peptide (oAβ) in the T-maze test in rats. PZ-1922 , but not intepirdine, restored levels of biomarkers characteristic of the debilitating effects of oAβ. These data support the potential of a multitarget approach involving the joint modulation of 5-HT 6 R/5-HT 3 R/MAO-B in AD.

Salt bridge (SB, double-charge-assisted hydrogen bonds) formation is one of the strongest molecular non-covalent interactions in biological systems, including ligand-receptor complexes. In the case of G-protein-coupled receptors, such an interaction is formed by the conserved aspartic acid (D3.32) residue and the basic moiety of the aminergic ligand. This study aims to determine the influence of the substitution pattern at the basic nitrogen atom and the geometry of the amine moiety at position 4 of 1 H -pyrrolo[3,2- c ]quinoline on the quality of the salt bridge formed in the 5-HT 6 receptor and D 3 receptor. To reach this goal, we synthetized and biologically evaluated a new series of 1 H -pyrrolo[3,2- c ]quinoline derivatives modified with various amines. The selected compounds displayed a significantly higher 5-HT 6 R affinity and more potent 5-HT 6 R antagonist properties when compared with the previously identified compound PZ-1643 , a dual-acting 5-HT 6 R/D 3 R antagonist; nevertheless, the proposed modifications did not improve the activity at D 3 R. As demonstrated by the in silico experiments, including molecular dynamics simulations, the applied structural modifications were highly beneficial for the formation and quality of the SB formation at the 5-HT 6 R binding site; however, they are unfavorable for such interactions at D 3 R.

Sydnones are heterocyclic compounds which display important biological activities, including their abilities to react in 1,3-dipolar additions for applications in the development of new prodrugs. Capitalizing on our preliminary work on the mechanosynthesis of sydnones, an extension of this work to two related families of molecules, diarylsydnones and iminosydnones is reported. A ball-milling approach towards the synthesis of diaryl sydnones was developed, a necessary step for the synthesis of potential sydnone-based ligands of metal complexes. A mechanochemistry-based synthesis of iminosydnones was optimized, including the preparation of active pharmaceutical ingredients (API) related to feprosidnine, linsidomine, mesocarb and molsidomine. This work demonstrated that the ball-milling procedures were efficient and time saving through avoiding purification steps, and reduced the use of organic solvents.

In addition to the canonical Gs adenylyl cyclase pathway, the serotonin type 6 receptor (5-HT 6 R) recruits additional signaling pathways that control cognitive function, brain development, and synaptic plasticity in an agonist-dependent and independent manner. Considering that aberrant constitutive and agonist-induced active states are involved in various pathological mechanisms, the development of biased ligands with different functional profiles at specific 5-HT 6 R-elicited signaling pathways may provide a novel therapeutic perspective in the field of neurodegenerative and psychiatric diseases. Based on the structure of SB-258585, an inverse agonist at 5-HT 6 R-operated Gs and Cdk5 signaling, we designed a series of 1-(arylsulfonyl-isoindol-2-yl)piperazine derivatives and synthesized them using a sustainable mechanochemical method. We identified the safe and metabolically stable biased ligand 3g , which behaves as a neutral antagonist at the 5-HT 6 R-operated Gs signaling and displays inverse agonist activity at the Cdk5 pathway. Inversion of the sulfonamide bond combined with its incorporation into the isoindoline scaffold switched the functional profile of 3g at Gs signaling with no impact at the Cdk5 pathway. Compound 3g reduced the cytotoxicity of 6-OHDA and produced a glioprotective effect against rotenone-induced toxicity in C8-D1A astrocyte cell cultures. In view of these findings, compound 3g can be considered a promising biased ligand to investigate the role of the 5-HT 6 R-elicited Gs and Cdk5 signaling pathways in neurodegenerative diseases.

The diverse signaling pathways engaged by serotonin type 6 receptor (5-HT 6 R) together with its high constitutive activity suggests different types of pharmacological interventions for the treatment of CNS disorders. Non-physiological activation of mTOR kinase by constitutively active 5-HT 6 R under neuropathic pain conditions focused our attention on the possible repurposing of 5-HT 6 R inverse agonists as a strategy to treat painful symptoms associated with neuropathies of different etiologies. Herein, we report the identification of compound 33 derived from the library of 2-aryl-1H-pyrrole-3-carboxamides as a potential analgesic agent. Compound 33 behaves as a potent 5-HT 6 R inverse agonist at Gs, Cdk5, and mTOR signaling. Preliminary ADME/Tox studies revealed preferential distribution of 33 to the CNS and placed it in the low-risk safety space. Finally, compound 33 dose-dependently reduced tactile allodynia in spinal nerve ligation (SNL)-induced neuropathic rats., (Copyright © 2021 The Author(s). Published by Elsevier Inc. All rights reserved.)

In line with recent clinical trials demonstrating that ondansetron, a 5-HT 3 receptor (5-HT 3 R) antagonist, ameliorates cognitive deficits of schizophrenia and the known procognitive effects of 5-HT 6 receptor (5-HT 6 R) antagonists, we applied the hybridization strategy to design dual-acting 5-HT 3 /5-HT 6 R antagonists. We identified the first-in-class compound FPPQ , which behaves as a 5-HT 3 R antagonist and a neutral antagonist 5-HT 6 R of the Gs pathway. FPPQ shows selectivity over 87 targets and decent brain penetration. Likewise, FPPQ inhibits phencyclidine (PCP)-induced hyperactivity and displays procognitive properties in the novel object recognition task. In contrast to FPPQ , neither 5-HT 6 R inverse agonist SB399885 nor neutral 5-HT 6 R antagonist CPPQ reversed (PCP)-induced hyperactivity. Thus, combination of 5-HT 3 R antagonism and 5-HT 6 R antagonism, exemplified by FPPQ , contributes to alleviating the positive-like symptoms. Present findings reveal critical structural features useful in a rational polypharmacological approach to target 5-HT 3 /5-HT 6 receptors and encourage further studies on dual-acting 5-HT 3 /5-HT 6 R antagonists for the treatment of psychiatric disorders.

The complex pathophysiology of depression, together with the limits of currently available antidepressants, has resulted in the continuous quest for alternative therapeutic strategies. Numerous findings suggest that pharmacological blockade of α 2 -adrenoceptor might be beneficial for the treatment of depressive symptoms by increasing both norepinephrine and serotonin levels in certain brain areas. Moreover, the antidepressant properties of 5-HT 7 receptor antagonists have been widely demonstrated in a large set of animal models. Considering the potential therapeutic advantages in targeting both α 2 -adrenoceptors and 5-HT 7 receptors, we designed a small series of arylsulfonamide derivatives of (dihydrobenzofuranoxy)ethyl piperidines as dually active ligands. Following green chemistry principles, the designed compounds were synthesized entirely using a sustainable mechanochemical approach. The identified compound 8 behaved as a potent α 2A /5-HT 7 receptor antagonist and displayed moderate-to-high selectivity over α 1 -adrenoceptor subtypes and selected serotonin and dopaminergic receptors. Finally, compound 8 improved performance of mice in the forced swim test, displaying similar potency to the reference drug mirtazapine.

Serotonin type 6 receptor (5-HT 6 R) has gained particular interest as a promising target for treating cognitive deficits, given the positive effects of its antagonists in a wide range of memory impairment paradigms. Herein, we report on degradation of the 1 H -pyrrolo[3,2- c ]quinoline scaffold to provide the 2-phenyl-1 H -pyrrole-3-carboxamide, which is devoid of canonical indole-like skeleton and retains recognition of 5-HT 6 R. This modification has changed the compound's activity at 5-HT 6 R-operated signaling pathways from neutral antagonism to inverse agonism. The study identified compound 27 that behaves as an inverse agonist of the 5-HT 6 R at the Gs and Cdk5 signaling pathways. Compound 27 showed high selectivity and metabolic stability and was brain penetrant. Finally, 27 reversed scopolamine-induced memory decline in the novel object recognition test and exhibited procognitive properties in the attentional set-shifting task in rats. In light of these findings, 27 might be considered for further evaluation as a new cognition-enhancing agent, while 2-phenyl-1 H -pyrrole-3-carboxamide might be used as a template for designing 5-HT 6 R inverse agonists.

Chronic neuropathic pain is a highly disabling syndrome that is poorly controlled by currently available analgesics. Here, we show that painful symptoms and associated cognitive deficits induced by spinal nerve ligation in the rat are prevented by the administration of serotonin 5-HT 6 receptor inverse agonists or by the mTOR inhibitor rapamycin. In contrast, they are not alleviated by the administration of 5-HT 6 receptor neutral antagonists. Likewise, activation of mTOR by constitutively active 5-HT 6 receptors mediates allodynia in oxaliplatin-induced peripheral neuropathy in rats but not mechanical nociception in healthy rats. Furthermore, both painful and co-morbid cognitive symptoms in neuropathic rats are strongly reduced by intrathecal delivery of a cell-penetrating peptide that disrupts 5-HT 6 receptor/mTOR physical interaction. Collectively, these findings demonstrate a deleterious influence of non-physiological mTOR activation by constitutively active spinal 5-HT 6 receptors upon painful and cognitive symptoms in neuropathic pains of different etiologies. They suggest that targeting the constitutive activity of 5-HT 6 receptors with inverse agonists or disrupting the 5-HT 6 receptor/mTOR interaction might be valuable strategies for the alleviation of neuropathic pain and cognitive co-morbidities., (Copyright © 2020 The Authors. Published by Elsevier Ltd.. All rights reserved.)

The use of ball-mills enabled the straightforward synthesis of a variety of silver(i) complexes featuring challenging NHC ligands. Sterically hindered including electron-poor or with very low solubility imidazolium salts were ground with silver(i) oxide to furnish heteroleptic or homoleptic complexes in high yields and short reaction times. The synthesis of heteroleptic bis-NHC silver(i) complexes was also performed for the first time in a ball mill. The efficiency and rapidity of the mechanochemical approach enabled the generation of a library of unprecedented NHC silver complexes, whose cytotoxicity on the HCT116 colorectal cancer cell line was evaluated providing a rare example of medicinal mechanochemistry. The cationic silver complexes were found to be more potent than the neutral analogues, with IC50 values down to 21 nM and 256 times more potent than cisplatin.

A mechanochemical procedure was developed to obtain PZ-1361 , a potent and selective 5-HT 7 receptor antagonist, with antidepressant properties in rodents. The elaborated protocol offered several advantages over classical batch synthesis, including improvement of the overall yield (from 34% to 64%), reduction of reaction time (from 60 to 5.5 h), limitation of the use of toxic solvents, and the formation of byproducts. This approach represents a rare example of the synthesis of biologically active compounds exclusively performed using mechanochemical reactions.

Sydnones are mesioionic compounds studied for years for their versatile reactivity in substitution reactions, sydnone-alkyne or sydnone-alkene cycloaddition reactions. This perspective article focuses on the use of sydnones in coordination complexes, either through a metalation on one of the carbons of the sydnone ring, its modification to obtain polydentate ligands, or its use as a polar moiety that could influence the properties of the final complex. Such compounds are valuable either from a synthetic point of view or for their biological properties.

N-Phenyl-4-(2-pyridinyl) sydnone was shown to act as a four-electron donor N,O-ligand in unprecedented coordination complexes featuring three different metallic centers (Co, Cu, and Zn). Starting with various anilines, the use of a ball-mill efficiently enabled the synthesis of N-arylglycines, subsequent nitrosylation and cyclization into sydnones, and further metalation.

In light of the multifactorial origin of neurodegenerative disorders and some body of evidence indicating that pharmacological blockade of serotonin 5-HT 6 and dopamine D 3 receptors might be beneficial for cognitive decline, we envisioned ( S )-1-[(3-chlorophenyl)sulfonyl]-4-(pyrrolidine-3-yl-amino)-1 H -pyrrolo[3,2- c ]quinoline (CPPQ), a neutral antagonist of 5-HT 6 R, as a chemical template for designing dual antagonists of 5-HT 6 /D 3 receptors. As shown by in vitro experiments, supported by quantum chemical calculations and molecular dynamic simulations, introducing alkyl substituents at the pyrrolidine nitrogen of CPPQ, fulfilled structural requirements for simultaneous modulation of 5-HT 6 and D 3 receptors. The study identified compound 19 (( S )-1-((3-chlorophenyl)sulfonyl)- N -(1-isobutylpyrrolidin-3-yl)-1 H -pyrrolo[3,2- c ]quinolin-4-amine), which was classified as a dual 5-HT 6 /D 3 R antagonist ( K i(5-HT6) = 27 nM, K i(D3) = 7 nM). Compound 19 behaved as a neutral antagonist at G s signaling and had no influence on receptor-operated, cyclin-dependent kinase 5 (Cdk5)-dependent neurite growth. In contrast to the well characterized 5-HT 6 R antagonist intepirdine, compound 19 displayed neuroprotective properties against astrocyte damage induced by doxorubicin, as shown using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium (MTT) staining to assess cell metabolic activity and lactate dehydrogenase (LDH) release as an index of cell membrane disruption. This feature is of particular importance considering the involvement of loss of homeostatic function of glial cells in the progress of neurodegeneration. Biological results obtained for 19 in in vitro tests, translated into procognitive properties in phencyclidine (PCP)-induced memory decline in the novel object recognition (NOR) task in rats.

Organometallic complexes: these two words jump to the mind of the chemist and are directly associated with their utility in catalysis or as a pharmaceutical. Nevertheless, to be able to use them, it is necessary to synthesize them, and it is not always a small matter. Typically, synthesis is via solution chemistry, using a round-bottom flask and a magnetic or mechanical stirrer. This review takes stock of alternative technologies currently available in laboratories that facilitate the synthesis of such complexes. We highlight five such technologies: mechanochemistry, also known as solvent-free chemistry, uses a mortar and pestle or a ball mill; microwave activation can drastically reduce reaction times; ultrasonic activation promotes chemical reactions because of cavitation phenomena; photochemistry, which uses light radiation to initiate reactions; and continuous flow chemistry, which is increasingly used to simplify scale-up. While facilitating the synthesis of organometallic compounds, these enabling technologies also allow access to compounds that cannot be obtained in any other way. This shows how the paradigm is changing and evolving toward new technologies, without necessarily abandoning the round-bottom flask. A bright future is ahead of the organometallic chemist, thanks to these novel technologies.

A solvent-assisted mechanochemical approach to access symmetrical and mixed dinucleoside 5,5'-polyphosphates is reported. Under ball-milling conditions, nucleoside 5'-monophosphates were quantitatively activated using 1,1'-carbonyldiimidazole, forming their phosphorimidazolide derivatives. The addition of a nucleoside 5'-mono-, di- or triphosphate directly led to the formation of the corresponding dinucleotides. Benefits of the reported one-pot method include the use of unprotected nucleotides in their sodium or acid form, activation by the eco-friendly 1,1'-carbonyldiimidazole, non-dry conditions, short reaction time, high conversion rates, and easy setup and purification. This work offers new perspectives for the synthesis of nucleotide conjugates and analogues, combining the phosphorimidazolide approach and milling conditions., (© 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

A new "bicycle helmet"-like copper(ii),sodiumphenylsilsesquioxane Ph12Si12O12(OH)(O-)11Cu5Na(bipy)3(H2O) exhibited high catalytic efficiency in two homogeneous reactions: (i) functionalization of C-H compounds; (ii) formation of benzamides from alcohols.

Unusual high-cluster (Cu 9 ) cage phenylsilsesquioxanes were obtained via complexation of in situ Cu II ,Na-silsesquioxane species formed with phenanthroline and neocuproine. In the first case, phenanthroline, acting as "a silent ligand" (not participating in the composition of the final product), favors the formation of an unprecedented cagelike phenylsilsesquioxane of Cu 9 Na 6 nuclearity, 1. In the second case, neocuproine ligands withdraws two Cu ions from the metallasilsesquioxane matrix, producing two cationic fragments Cu + (neocuproine) 2 . The remaining metallasilsesquioxane is rearranged into an anionic cage of Cu 9 Na 4 nuclearity, finalizing the formation of a specific ionic complex, 2. The impressive molecular architecture of both types of complexes, e.g., the presence of different (cyclic/acyclic) types of silsesquioxane ligands, was established by single-crystal X-ray diffraction studies. Compound 1 was revealed to be highly active in the oxidative amidation of benzylic alcohol and the catalyst loading could be reduced down to 100 ppm of Cu. Catalytic studies of compound 1 demonstrated its high activity in hydroperoxidation of alkanes with H 2 O 2 and oxidation of alcohols to ketones with tert-BuOOH.

A new representative of an unusual family of metallagermaniumsesquioxanes, namely the heterometallic cagelike phenylgermsesquioxane (PhGeO 2 ) 12 Cu 2 Fe 5 (O)OH(PhGe) 2 O 5 (bipy) 2 (2), was synthesized and structurally characterized. Fe(III) ions of the complex are coordinated by oxa ligands: (i) cyclic (PhGeO 2 ) 12 and acyclic (Ph 2 Ge 2 O 5 ) germoxanolates and (ii) O 2- and (iii) HO - moieties. In turn, Cu(II) ions are coordinated by both oxa (germoxanolates) and aza ligands (2,2'-bipyridines). This "hetero-type" of ligation gives in sum an attractive pagoda-like molecular architecture of the complex 2. Product 2 showed a high catalytic activity in the oxidation of alkanes to the corresponding alkyl hydroperoxides (in yields up to 30%) and alcohols (in yields up to 100%) and in the oxidative formation of benzamides from alcohols (catalyst loading down to 0.4 mol % in Cu/Fe).

The synthesis, composition, and catalytic properties of a new family of hexanuclear Cu(II)-based phenylsilsesquioxanes are described here. Structural studies of 17 synthesized compounds revealed the general principle underlying their molecular topology: viz., a central metal oxide layer consisting of two Cu 3 trimers is coordinated by two cyclic [PhSiO 1.5 ] 5 siloxanolate ligands to form a skewed sandwich architecture with the composition [(PhSiO 1.5 ) 10 (CuO) 6 ] 2+ . In addition to this O ligation by the siloxanolate rings, two opposite copper ions are additionally coordinated by the nitrogen atoms of corresponding N ligand(s), such as 2,2'-bipyridine (compounds 1-9), 1,10-phenanthroline (compounds 10-13), mixed 1,10-phenanthroline/2,2'-bipyridine (compound 14), or bathophenanthroline (compounds 15-17). Finally, the charge balance is maintained by two HO - (compounds 1-7, 10-13, and 15-17), two H 3 CO - (compound 8), or two CH 3 COO - (compounds 9 and 14) anions. Complexes 1 and 10 exhibited a high activity in the oxidative amidation oxidation of alcohols. Compounds 1, 10, and 15 are very efficient homogeneous catalysts in the oxidation of alkanes and alcohols with peroxides.

Mechanical forces induced by ball-milling agitation enabled the highly efficient and widely applicable synthesis of Cu-carbene complexes from N , N -diaryl-imidazolium salts and metallic copper. The required amount of gaseous dioxygen and insoluble copper could be reduced down to stoichiometric quantities, while reaction rates clearly outperformed those obtained in solution. Utilisation of Cu(0) as the copper source enabled the application of this approach to a wide array of N , N -diaryl-imidazolium salts (Cl - , BF 4 - and PF 6 - ) that transferred their counter anion directly to the organometallic complexes. Cu-NHC complexes could be produced in excellent yields, including utilisation of highly challenging substrates. In addition, five unprecedented organometallic complexes are reported.

A series of four unprecedented heterometallic metallagermsesquioxanes were synthesized. Their cage-like architectures have a unique type of molecular topology consisting of the hexairon oxo {Fe 6 O 19 } core surrounded in a triangular manner by three cyclic germoxanolates [PhGe(O)O] 5 . This structural organization induces antiferromagnetic interactions between the Fe III ions through the oxygen atoms. Evaluated for this first time in catalysis, these compounds showed a high catalytic activity in the oxidation of alkanes and the oxidative formation of benzamides from alcohols., (© 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

A user-friendly and general mechanochemical method was developed to access rarely described NHC (N-heterocyclic carbene) silver(i) complexes featuring N,N-diarylimidazol(idin)ene ligands and non-coordinating tetrafluoroborate or hexafluorophosphate counter anions. Comparison with syntheses in solution clearly demonstrated the superiority of the ball-milling conditions.

A silver-catalyzed cycloisomerization reaction of a series of o-alkynylbenzohydroxamic acids is reported. Several 5-exo-dig and 6-endo-dig modes of cyclization were observed with the nitrogen or oxygen atoms of the amide group acting as nucleophiles. The selectivity was strongly dependent on the silver salt used and on the presence of triphenylphosphine as an additive. Indeed, while the use of Ag 2 O at room temperature allowed the isolation of isobenzofuran-1-one oximes (7 compounds, 48-92% yield), [Ag(Im)] n with the concomitant addition of 2 equiv of PPh 3 led to a switch in selectivity and to a family of isoindolin-1-ones (10 compounds, 59-87%).

Modulators of the serotonin 5-HT6 receptor (5-HT6R) offer a promising strategy for the treatment of the cognitive deficits that are associated with dementia and Alzheimer's disease. Herein, we report the design, synthesis, and characterization of a novel class of 5-HT6R antagonists that is based on the 1H-pyrrolo[3,2-c]quinoline core. The most active compounds exhibited comparable binding affinity to the reference compound, SB-742457, and markedly improved selectivity. Lead optimization led to the identification of (S)-1-[(3-chlorophenyl)sulfonyl]-4-(pyrrolidine-3-yl-amino)-1H-pyrrolo[3,2-c]quinoline (14) (Ki = 3 nM and Kb = 0.41 nM). Pharmacological characterization of the 5-HT6R's constitutive activity at Gs signaling revealed that 14 behaved as a neutral antagonist, while SB-742457 was classified as an inverse agonist. Both compounds 14 and SB-742457 reversed phencyclidine-induced memory deficits and displayed distinct procognitive properties in cognitively unimpaired animals (3 mg/kg) in NOR tasks. Compounds 14 and SB-742457 were also active in the Vogel test, yet the anxiolytic effect of 14 was 2-fold higher (MED = 3 mg/kg). Moreover, 14 produced, in a 3-fold higher dose (MED = 10 mg/kg), antidepressant-like effects that were similar to those produced by SB-742457 (MED = 3 mg/kg). Together, these data suggest that the 4-(pyrrolidine-3-yl-amino)-1H-pyrrolo[3,2-c]quinoline scaffold is an attractive molecular framework for the development of procognitive agents. The results are promising enough to warrant further detailed mechanistic studies on the therapeutic potential of 5-HT6R antagonists and inverse agonists for the treatment of cognitive decline and depression/anxiety symptoms that are comorbidities of Alzheimer's disease.

The absence of solvent, associated with intensive mechanical agitation, allowed the first mechanosynthesis of high-value silver(I)-carbene complexes and the corresponding N,N-dialkylimidazolium precursors. This procedure gave outstanding results in terms of yield and reaction time, when compared to solution-based conditions previously described in literature, and was generalized to unprecedented compounds. Silver(I)-carbene complexes could either be obtained from N,N-dialkylimidazolium salts or directly from imidazole and alkyl halides in a one-pot two-step procedure without isolating the imidazolium intermediate. Additionally, an efficient one-pot three-step sequence, including imidazole alkylation, silver metalation, and transmetalation is reported., (© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

The transmetalation of bimetallic copper-sodium silsesquioxane cages, namely, [(PhSiO1.5 )10 (CuO)2 (NaO0.5 )2 ] ("Cooling Tower"; 1), [(PhSiO1.5 )12 (CuO)4 (NaO0.5 )4 ] ("Globule"; 2), and [(PhSiO1.5 )6 (CuO)4 (NaO0.5 )4 (PhSiO1.5 )6 ] ("Sandwich"; 3), resulted in the generation of three types of hexanuclear cylinder-like copper silsesqui- oxanes, [(PhSiO1.5 )12 (CuO)6 (C4 H9 OH)2 (C2 H5 OH)6 ] (4), [(PhSiO1.5 )12 (CuO)6 (C4 H8 O2 )4 (PhCN)2 (MeOH)4 ] (5), and [(PhSiO1.5 )12 (CuO)6 (NaCl)(C4 H8 O2 )12 (H2 O)2 ] (6). The products show a prominent "solvating system-structure" dependency, as determined by X-ray diffraction. Topological analysis of cages 1-6 was also performed. In addition, DFT theory was used to examine the structures of the Cooling Tower and Cylinder compounds, as well as the spin density distributions. Compounds 1, 2, and 5 were applied as catalysts for the direct oxidation of alcohols and amines into the corresponding amides. Compound 6 is an excellent catalyst in the oxidation reactions of benzene and alcohols., (© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Phosphine-free palladium-catalyzed Mizoroki-Heck reaction was performed using ball-milling in polyethylene glycol under mild conditions. Good to excellent yields of coupling products were obtained. This activation technique also allowed the concomitant formation of round shaped Pd-PEG nanoparticles that were characterized by TEM analysis.

A family of furoquinolines were efficiently obtained through a tandem acetalization/cycloisomerization process catalyzed by (5 mol%) silver imidazolate polymer and triphenylphosphine, and diversity was brought by the use of 7 different alcohol groups. From these furoquinolines, 3 examples of reduced derivatives could be obtained (d.r. up to 94 : 6), 10 different spiroketal derivatives by hetero-Diels-Alder reaction (d.r. up to 20 : 1), 8 hetero-[5,5]-spirocycles by cycloaddition with dibromoformaldoxime (d.r. up to 86 : 14) and finally 6 hetero-[5,6]-spirocycles by [4 + 2] cycloaddition with ethyl 3-bromo-2-(hydroxyimino)propanoate (d.r. up to 90 : 10).

The use of phosphites in second generation, ruthenium-based olefin metathesis pre-catalysts leads to an improvement in catalyst stability and activity at low catalyst loadings., (This journal is © The Royal Society of Chemistry 2011)

The synthesis and characterization of two new ruthenium indenylidene complexes [RuCl(2)(SIPr)(Py)(Ind)] 6 and [RuCl(2)(SIPr)(3-BrPy)(Ind)] 7 featuring the sterically demanding N-heterocyclic carbene 1,3-bis(2,6-di isopropylphenyl)-4,5-dihydroimidazol-2-ylidene (SIPr) are reported. Remarkable activity was observed with these complexes in ring closing, enyne, and cross metathesis of olefins at low catalyst loadings. The performance of SIPr-bearing complexes 6 and 7 as well as [RuCl(2)(SIPr)(PCy(3))(Ind)] 5 in ring opening metathesis polymerization is also disclosed. This work highlights the enormous influence of the neutral "spectator" ligands on catalyst activity and stability., (Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

The Pd-catalyzed intramolecular allylic alkylation of unsaturated amides to give γ- and δ-lactams has been studied in the presence of chiral ligands. Ligand (R)-3,5-tBu-MeOBIPHEP (MeOBIPHEP = 6,6'-dimethoxybiphenyl-2,2-diyl)bis(diphenylphosphine)) afforded the best results and allowed the cyclization reactions to take place in up to 94:6 enantiomeric ratio. A model Pd-allyl complex has been prepared and studied through NMR spectroscopic analysis, which provided insight into the processes responsible for the observed enantiomeric ratios. DFT studies were used to characterize the diastereomeric reaction pathways. The calculated energy differences were in good agreement with the experimentally observed enantiomeric ratios., (Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

We describe the synthesis of commonly used free N-heterocyclic carbenes (NHCs), 1,3-bis-(2,4,6-trimethylphenyl)imidazol-2-ylidene (IMes) and 1,3-bis-(2,6-diisopropylphenyl)imidazol-2-ylidene (IPr), and of the two corresponding ruthenium-based metathesis complexes. The complex containing IMes was found to be highly efficient in macrocyclizations involving ring-closing metatheses (RCM), whereas the complex featuring the IPr ligand shows excellent activity in both RCM and cross metathesis because of its greater stability. The free carbenes IMes and IPr are isolated in four steps, with an overall yield of ∼50%. They are then used to replace a labile phosphine in precatalysts belonging to two families of ruthenium-containing complexes, benzylidene and indenylidene types, respectively. Such complexes are isolated as analytically pure compounds with 77% and 95% yield. The total time for the synthesis of the free NHCs is 56 h, and incorporation in complexes requires an additional 4-5 h.

The steric and electronic influence of backbone substitution in IMes-based (IMes = 1,3-bis(2,4,6-trimethylphenyl)imidazol-2-ylidene) N-heterocyclic carbenes (NHC) was probed by synthesizing the [RhCl(CO)₂(NHC)] series of complexes to quantify experimentally the Tolman electronic parameter (electronic) and the percent buried volume (%V(bur), steric) parameters. The corresponding ruthenium-indenylidene complexes were also synthesized and tested in benchmark metathesis transformations to establish possible correlations between reactivity and NHC electronic and steric parameters.

The synthesis, characterisation and catalytic behaviour of ruthenium indenylidene complexes bearing an N-heterocyclic carbene and triisopropylphosphite are described.

Allylic sulfoxides, via [2,3]-sigmatropic rearrangement and oxidative addition of the resulting allylic sulfenate esters to Pd(0), are found to be excellent precursors of sulfenate anions. This hitherto unknown reactivity is applied in a new Pd(0)-catalyzed domino sequence involving sulfenate anion generation followed by arylation to afford aryl sulfoxides.

The compounds 4,5-dimethyl-N,N'-bis(2,6-diisopropylphenyl)imidazol-2-ylidene silver chloride [AgCl(IPr(Me))] and 4,5-dimethyl-N,N'-bis(2,6-diisopropylphenyl)imidazol-2-ylidene gold(I) chloride [AuCl(IPr(Me))] have been synthesized. The attempted synthesis of the corresponding 4,5-dimethyl-N,N'-bis(2,6-diisopropylphenyl)imidazol-2-ylidene gold(III) chloride by oxidative addition of chlorine gas on allowed for the formation of the expected complex, concomitantly with , resulting from a chlorination of a methyl group situated in the backbone of the NHC (N-heterocyclic carbene). Additionally, the buried volume %V(bur) of the IPr(Me) ligand in [AgCl(IPr(Me))] and [AuCl(IPr(Me))] complexes was calculated and compared to %V(bur) of more classical NHCs. This quantification of the steric hinderance of the IPr(Me) ligand reveals the influence of the substituent modulation in the backbone of NHCs.