Search results for "Reti"

6-Polyamino-substituted quinolines: synthesis and multiple metal (CuII, HgIIand ZnII) monitoring in aqueous media

2019

Chemoselective palladium-catalyzed arylation of polyamines with 6-bromoquinoline has been explored to prepare chelators for the detection of metal cations in aqueous media. The introduction of a single aromatic moiety into non-protected polyamine molecules was achieved using the commercially available Pd(dba)2/BINAP precatalyst to afford nitrogen chelators, in which the aromatic signalling unit is directly attached to the polyamine residue. Water-soluble receptors were then synthesized using N-alkylation of these polyamines by hydrophilic coordinating residues. By combining rich photophysical properties of the 6-aminoquinoline unit with a high coordination affinity of chelating polyamines a…

Direct Difluorination–Hydroxylation, Trifluorination, and C(sp2)–H Fluorination of Enamides

2018

A direct double functionalization involving both difluorination and hydroxylation of enamides is reported. With the appropriate combination of an electrophilic fluorinating reagent and H2O, the most convenient and ecofriendly hydroxylating agent, the preparation of 3-(difluoroalkyl)-3-hydroxyisoindolin-1-ones was achieved under basic or Bronsted acidic conditions. Suitable conditions for trifluorination as well as C(sp2)–H fluorination were also identified. Subsequent asymmetric functionalization of the obtained gem-difluorinated products has also been demonstrated.

Organocatalytic Oxidation of Secondary Alcohols Using 1,2-Di(1-naphthyl)-1,2-ethanediamine (NEDA)

2014

Diamine, 1,2-di(1-naphthyl)-1,2-ethanediamine (NEDA), efficiently catalyzes the oxidation of alcohols by using TBHP as an oxidant. Notably, secondary benzyl alcohols are oxidized in almost quantitative yields, and the catalyst also displays high activity towards even hindered cycloaliphatic secondary alcohols. With enantiopure (R,R)-NEDA, oxidative kinetic resolution can be realized and depending on the alcohol ee up to 99 % are achieved.

Supported Polyhedral Oligomeric Silsesquioxane-Based (POSS) Materials as Highly Active Organocatalysts for the Conversion of CO2

2018

Very high turnover numbers (TON) and productivity values up to 7875 and 740 respectively have been obtained for the conversion of CO2 into cyclic carbonates by using hybrid materials based on imidazolium modified polyhedral oligomeric silsesquioxanes (POSS-Imi) grafted on amorphous silica (SiO2) and mesostructured SBA-15. The heterogeneous organocatalysts were easily prepared via a straightforward synthetic procedure allowing to generate high local concentration spots of imidazolium active sites surrounding the POSS core. This synthetic procedure is also a promising approach for the design of a wide library of hybrid functional materials. The materials do not possess other co-catalytic spec…

N-Cobaltocenium Amide as Reactive Nucleophilic Reagent for Donor–Acceptor Bimetallocenes

2017

Deprotonation of the aminocobaltocenium ion [Cc-NH2]+ ([H-1]+) generates the nucleophilic imine CcNH (1). Reaction of 1 with acid chlorides R–COCl (R = Ph, Fc, and Cc+) yields the reference amide [Ph-CO-NH-Cc]+ (2+) and the amide-linked hetero- and homobimetallocenes [Fc-CO-NH-Cc]+ (3+) and [Cc-CO-NH-Cc]2+ (42+), respectively. Cation–anion interactions of charged amides 2+–42+ in the solid state and in solution are probed by single crystal X-ray diffraction and NMR and IR spectroscopy. Intramolecular metal–metal interactions in donor–acceptor heterobimetallocene 3+ and in mixed-valent homobimetallocene 4+ (prepared electrochemically) are discussed within the Marcus–Hush framework aided by s…

Supramolecular assemblies and photophysical properties of ionic homo- and heteronuclear metallophilic complexes

2019

Abstract The synthesis of two dinuclear ionic complexes with chemical formula [Au(PR 3 ) 2 ][Au(C ≡ CC 5 H 4 N-4) 2 ] that contain the water soluble phosphines, PR 3 , PTA (1, 3,5-triaza-7-phosphaadamantane, 1 ) and DAPTA (3,7-diacetyl-1,3,7-triaza-5-phosphabicyclo[3.3.1]nonane, 2 ) is herein described. The differences on their intermolecular reorganization have been analyzed and compared with the previously reported for the neutral complexes [Au(PR 3 )(C ≡ CC 5 H 4 N-4)]. It has been evidenced that the reorganization of the ligands giving rise to the dinuclear ionic complexes produces a complete change in the properties giving rise to Au⋯Au intermolecular assemblies. These aurophilic conta…

A metal-free and regioselective approach to (Z)-β-fluorovinyl sulfones and their chemoselective hydrogenation to β-fluoroalkyl sulfones

2018

Abstract A highly regioselective, metal-free hydrofluorination reaction of alkynyl sulfones was developed using TBAF—one of the cheapest and most commonly available fluoride sources. In addition, the reactivity of the resulting β-fluorovinyl sulfones was studied, focusing on their selective hydrogenation reaction. Both β-fluorovinyl sulfones and their hydrogenation products β-fluoroalkyl sulfones may find applications in medicinal and agrochemical sciences.

Unveiling the high reactivity of cyclohexynes in [3 + 2] cycloaddition reactions through the molecular electron density theory

2018

[3 + 2] cycloaddition (32CA) reactions of cyclohexyne, a cyclic strained acetylene, with methyl azide and methoxycarbonyl diazomethane have been studied within the Molecular Electron Density Theory (MEDT) at the MPWB1K/6-311G(d) computational level. These 32CA reactions, which take place through a one-step mechanism involving highly asynchronous transition state structures, proceed with relatively low activation enthalpies of 6.0 and 4.3 kcal mol-1, respectively, both reactions being strongly exothermic. The reactions are initiated by the creation of a pseudoradical center at one of the two acetylenic carbons of cyclohexyne with a very low energy cost, 1.0 kcal mol-1, which promotes the eas…

Cobaltocenium substituents as electron acceptors in photosynthetic model dyads

2017

Abstract Cobaltocenium carboxylic acid hexafluorophosphate has been attached to a zinc(II) meso-tetraphenyl porphyrin chromophore via an amide linkage. Optical and electrochemical studies reveal that the metallocene and the porphyrin interact only negligibly in the ground state of the dyad. Photoinduced charge-shift from the zinc porphyrin to the cobaltocenium substituent to give the zinc porphyrin radical cation and the cobaltocene occurs upon exciting the porphyrin with light. Steady state emission, time-resolved fluorescence and transient absorption pump–probe spectroscopy in addition to density functional theory calculations suggest that the charge shift to the cobaltocenium substituent…

2020

Teraryl-based alpha-helix mimetics have resulted in efficient inhibitors of protein-protein interactions (PPIs). Extending the concept to even longer oligoarene systems would allow for the mimicking of even larger interaction sites. We present a highly efficient synthetic modular access to quateraryl alpha-helix mimetics, in which, at first, two phenols undergo electrooxidative dehydrogenative cross-coupling. The resulting 4,4′-biphenol is then activated by conversion to nonaflates, which serve as leaving groups for iterative Pd-catalyzed Suzuki-cross-coupling reactions with suitably substituted pyridine boronic acids. This work, for the first time, demonstrates the synthetic efficiency of …