Visible-Light-Mediated Deaminative Alkylation of Primary Amines with Silacarboxylic Acids via Isonitrile Formation.

The functionalization of the C-N bond of amines is a straightforward strategy for the construction of complex scaffolds or for the late-stage functionalization of pharmaceuticals. Herein, we describe a photoredox-catalyzed strategy for the deaminative alkylation of primary amine-derived isonitriles that provides unnatural amino acid derivatives under mild conditions. The use of silacarboxylic acids as silyl radical precursors enables the generation of carbon-centered radicals that allow the construction of Csp-Csp bonds via a Giese-type addition, avoiding the undesired hydrodeamination product.

Csp-Csp Coupling of Isonitriles and (Hetero)arenes through a Photoredox-Catalyzed Double Decyanation Process.

Herein, we demonstrate the ability of isonitriles to be used as alkyl radical precursors in a photoredox-catalyzed transformation involving selective C-N cleavage and Csp-Csp bond formation. This protocol allows for the preparation of functionalized heteroarenes from readily available isonitriles through a decyanation process. The reaction is general for primary, secondary, and tertiary substrates, including amino acid derivatives and druglike molecules.

Unnatural Cyclopeptide Synthesis via Cu-Catalyzed 1,3-Dipolar Cycloaddition of Azomethine Ylides.

Cyclic peptides are valued synthetic targets in organic and medicinal chemistry. Herein, we report an efficient strategy for the synthesis of unnatural cyclic peptides via the Cu-catalyzed 1,3-dipolar cycloaddition of azomethylene ylides. Linear precursors of different lengths and bearing diverse amino acids (26 examples) are shown to be compatible with this method, affording good yields and complete -diastereoselectivities.

Trityl isocyanide as a general reagent for visible light mediated photoredox-catalyzed cyanations.

A photoredox catalytic strategy has been developed to enable the functionalization of a variety of commercially available, structurally different radical precursors by the use of a bench-stable isonitrile as an efficient cyanating reagent. Specifically, a radical-based reaction has provided a mild and convenient procedure for the cyanation of primary, secondary and tertiary radicals derived from widely accessible sp-hybridized carboxylic acids, alcohols and halides under visible light irradiation. The reaction tolerates a variety of functional groups and it represents a complementary method for the cyanation of structurally different scaffolds that show diverse native functionalities, expanding the scope of previously reported methodologies.

Bicarbonate-binding catalysis for the enantioselective desymmetrization of keto sulfonium salts.

Herein, an enantioselective desymmetrization of cyclic keto sulfonium salts through enantioselective deprotonation/ring opening process by anion-binding catalysis is presented. We report a squaramide/HCO complex as catalytic active species which is able to stereo-differentiate two enantiomeric protons, triggering the ring opening event taking advantage of the great tendency of sulfonium salts to act as leaving groups. Thus, this desymmetrization methodology give rise to β-methylsulfenylated sulfa-Michael addition type products with excellent yields and very good enantioselectivities.

Single walled carbon nanotubes covalently functionalized by a ruthenium complex for photocatalytic oxidations.

The covalent bonding of a ruthenium bipyridine complex derivative with the aromatic network of single walled carbon nanotubes (SWNT) through a stepwise protocol is presented, thus yielding the sample SWNT-Ru. To do that, an-amino decorated phenanthroline is bonded to the nanotube by means of the diazonium chemistry protocol, providing anchoring points for discrete organometallic units as depicted by the solid characterization techniques employed. The hybrid material, able to emit upon excitation, is active in the visible light-driven photocatalytic oxidation of organic sulfides to sulfoxides.

Atroposelective Synthesis of Axially Chiral Naphthylpyrroles by a Catalytic Asymmetric 1,3-Dipolar Cycloaddition/Aromatization Sequence.

A straightforward methodology for the enantioselective preparation of axially chiral 2-naphthylpyrroles has been developed. This protocol is based on a Cu/Fesulphos-catalyzed highly enantioselective 1,3-dipolar cycloaddition of an azomethine ylide followed by pyrrolidine alkylation and pyrrolidine to pyrrole oxidation. The mild conditions employed in the DDQ/blue light-mediated aromatization process facilitate an effective central-to-axial chirality transfer affording the corresponding pyrroles with high atroposelectivity.

Synthesis, Structure, and Photophysical Properties of Platinum(II) (,,') Pincer Complexes Derived from Purine Nucleobases†.

The synthesis of a series of Pt{κ-,,'-[L]}X (X = Cl, RC≡C) pincer complexes derived from purine and purine nucleosides is reported. In these complexes, the 6-phenylpurine skeleton provides the ,-cyclometalated fragment, whereas an amine, imine, or pyridine substituent of the phenyl ring supplies the additional '-coordination point to the pincer complex. The purine ,-fragment has two coordination positions with the metal (1 and 7), but the formation of the platinum complexes is totally regioselective.

Base-Induced Sulfoxide-Sulfenate Rearrangement of 2-Sulfinyl Dienes for the Regio- and Stereoselective Synthesis of Enantioenriched Dienyl Diols.

The base-induced [2,3]-sigmatropic rearrangement of a series of enantiopure 2-sulfinyl dienes has been examined and optimized using a combination of NaH and PrOH. The reaction takes place by allylic deprotonation of the 2-sulfinyl diene to give a bis-allylic sulfoxide anion intermediate that after protonation undergoes sulfoxide-sulfenate rearrangement. Different substitution at the starting 2-sulfinyl dienes has allowed us to study the rearrangement finding that a terminal allylic alcohol is determinant to achieve complete regioselectivity and high enantioselectivities (90:10-95:5) with the sulfoxide as the only element of stereocontrol.

Enantioselective Suzuki cross-coupling of 1,2-diboryl cyclopropanes.

Herein, we describe the catalytic enantioselective cross-coupling of 1,2-bisboronic esters. Prior work on group specific cross coupling is limited to the use of geminal bis-boronates. This desymmetrization provides a novel approach to prepare enantioenriched cyclopropyl boronates with three contiguous stereocenters, that could be further derivatized through selective functionalization of the carbon-boron bond.

Heteropolymetallic [FeFe]-Hydrogenase Mimics: Synthesis and Electrochemical Properties.

The synthesis and electrochemical properties of tetranuclear [FeS]-hydrogenase mimic species containing Pt(II), Ni(II), and Ru(II) complexes have been studied. To this end, a new tetranuclear [FeS] complex containing a 5,5'-diisocyanide-2,2'-bipyridine bridging ligand has been designed and coordinated to the metal complexes through the bipyridine moiety. Thus, the tetranuclear [FeS] complex () coordinates to Pt(II), Ni(II) and Ru(II) yielding the corresponding metal complexes.

Ethylene Dimerization and Oligomerization Using Bis(phosphino)boryl Supported Ni Complexes.

We report the dimerization and oligomerization of ethylene using bis(phosphino)boryl supported Ni(II) complexes as catalyst precursors. By using alkylaluminum(III) compounds or other Lewis acid additives, Ni(II) complexes of the type (PBP)NiBr (R = Bu or Ph) show activity for the production of butenes and higher olefins. Optimized turnover frequencies of 640 mol·mol·s for the formation of butenes with 41(1)% selectivity for 1-butene using (PBP)NiBr, and 68 mol·mol·s for butenes production with 87.

Palladium-Catalyzed PIDA-Mediated δ-C(sp )-H Acetoxylation of Amino Acid Derivatives: Overriding Competitive Intramolecular Amination.

The selective δ-C(sp )-H acetoxylation of N-(SO Py)-protected amino acid derivatives has been accomplished by using palladium-catalysis and PhI(OAc) (PIDA) as both terminal oxidant and acetoxy source. The distinct structural and electronic features of the SO Py compared to more traditional carbonyl-based directing groups is essential to override the otherwise more favourable competitive intramolecular C-H amination. The δ-site selectivity predominates over traditionally more favorable 5-membered cyclopalladation at competitive γ-CH .

A Graphene Acid - TiO Nanohybrid as Multifunctional Heterogeneous Photocatalyst for the Synthesis of 1,3,4-Oxadiazoles.

The immobilization of TiO nanoparticles on graphene acid (GA), a conductive graphene derivative densely functionalized with COOH groups, is presented. The interaction between the carboxyl groups of the surface and the titanium precursor leads to a controlled TiO heterogenization on the nanosheet according to microscopic and spectroscopic characterizations. Electronic communication shared among graphene and semiconductor nanoparticles shifts the hybrid material optical features toward less energetic radiation but maintaining the conductivity.

General electrochemical Minisci alkylation of -heteroarenes with alkyl halides.

Herein, we report, a general, facile and environmentally friendly Minisci-type alkylation of -heteroarenes under simple and straightforward electrochemical conditions using widely available alkyl halides as radical precursors. Primary, secondary and tertiary alkyl radicals have been shown to be efficiently generated and coupled with a large variety of -heteroarenes. The method presents a very high functional group tolerance, including various heterocyclic-based natural products, which highlights the robustness of the methodology.

Nickel-Catalysed Cross-Electrophile Coupling of Benzyl Bromides and Sulfonium Salts towards the Synthesis of Dihydrostilbenes.

A nickel-catalysed reductive cross-coupling reaction between benzyl sulfonium salts and benzyl bromides is reported. Simple, stable and readily available sulfonium salts have shown their ability as leaving groups in cross-electrophile coupling, allowing the formation of challenging sp -sp carbon-carbon bonds, towards the synthesis of interesting dihydrostilbene derivatives. In addition, benzyl tosyl derivatives have been demonstrated to be suitable substrates for reductive cross-coupling by in-situ formation of the corresponding sulfonium salt.

Isothiourea-catalysed enantioselective radical conjugate addition under batch and flow conditions.

The photocatalytic generation of α-amino radicals is combined with chiral isothiourea derived α,β-unsaturated acyl ammonium intermediates. The reaction proceeds a [3+2] radical-polar crossover mechanism to generate γ-lactams in good yields and enantioselectivities. The enantioselective radical conjugate addition was carried out under batch and flow conditions.

Continuous-flow synthesis of alkyl zinc sulfinates for the direct photofunctionalization of heterocycles.

A sustainable strategy for the alkylation of heterocycles is presented. The protocol relies on the generation and further in-line use of alkyl zinc sulfinates through a continuous-flow system. The environmentally friendly character of the protocol is assured by the use of a green solvent mixture, the presence of a metal free oxidant and low waste generation.

Electrocatalytic Behavior of Tetrathiafulvalene (TTF) and Extended Tetrathiafulvalene (exTTF) [FeFe] Hydrogenase Mimics.

TTF- and exTTF-containing [(μ-S)Fe(CO)] complexes have been prepared by the photochemical reaction of TTF or exTTF and [(μ-S)Fe(CO)]. These complexes are able to interact with PAHs. In the absence of air and in acid media an electrocatalytic dihydrogen evolution reaction (HER) occurs, similarly to analogous [(μ-S)Fe(CO)] complexes.

Revisiting the photochemical synthesis of [FeFe]-hydrogenase mimics: reaction optimization, mechanistic study and electrochemical behaviour.

The photoreaction of [(μ-S)Fe(CO)] and alkenes or alkynes has been optimized to readily obtain functionalized [FeFe]-hydrogenase mimics. Irradiation under low CO pressure in THF produces the corresponding photo-adducts in good/acceptable (alkenes/alkynes) yields, with retention of the starting olefin stereochemistry. DFT-calculations provide plausible reaction pathways in both, singlet and triplet states.

Proteostasis disturbances and endoplasmic reticulum stress contribute to polycystic liver disease: New therapeutic targets.

Background & Aims: Polycystic liver diseases (PLDs) are genetic disorders characterized by progressive development of multiple biliary cysts. Recently, novel PLD-causative genes, encoding for endoplasmic reticulum (ER)-resident proteins involved in protein biogenesis and transport, were identified. We hypothesized that aberrant proteostasis contributes to PLD pathogenesis, representing a potential therapeutic target.

Triazole-Containing [FeFe] Hydrogenase Mimics: Synthesis and Electrocatalytic Behavior.

Through a Cu-catalyzed Huisgen cycloaddition between terminal alkynes and azides (CuAAC) reaction, azide [(μ-SCH)N(4-NCH)Fe(CO)] has demonstrated to be a robust and versatile reagent able to incorporate the [(μ-SR)Fe(CO)] fragment on a wide range of substrates, ranging from aromatic compounds to nucleosides, metallocenes, or redox and luminescent markers. The [FeFe]/[FeFe] and [FeFe]/[FeFe] reduction potentials of the triazole derivatives prepared are comparable to those of other aminodithiolate (adt) Fe-Fe hydrogenase mimics. The presence of the triazole linker influences the electrochemical behavior of these complexes depending on the strength of the acid employed.