Photocatalytic Three-Component Reaction for the Synthesis of Multifunctional Diaryl Sulfides.

A photocatalytic three-component reaction of a nitroarene, a thiophenol, and a ketone for the synthesis of multifunctional diaryl sulfides was reported using a nitro group as the nitrogen source and thiophenol as the sulfur source. Thiophenol also serves as a proton donor to reduce nitroarene to arylamine as a key intermediate for the formation of C-N and C-S bonds. Good functional group tolerance and mild reaction conditions make this method have practical synthetic value for diversified multifunctional diaryl sulfides.

Visible-Light-Mediated Three-Component Decarboxylative Coupling Reactions to Synthesize 1,4-Diol Monoethers.

An efficient approach for 1,2-difunctionalization of aromatic olefins and the synthesis of functionalized 1,4-diols monoethers has been established via a photoinduced three-component reaction of an α-alkoxycarboxylic acid, an aromatic olefin, and an aldehyde. The reaction proceeds by photoinduced oxidative decarboxylation of the carboxylic acid followed by the addition of the α-alkoxyalkyl radical to the olefin, one-electron reduction of the addition radical, and the nucleophilic attack of the resulting carbanion to the aldehyde. Besides the convenient one-pot protocol of the three-component reaction, this method offers several other advantages, including good functional group tolerance for the three substrates, gentle reaction conditions, and ease of scaling up. The reaction mechanism has been investigated through free radical trapping experiment and isotope labeling experiments.

Visible-light induced three-component reaction for α-aminobutyronitrile synthesis by C-C bond formation using quantum dots as photocatalysts.

We describe a three-component reaction of malononitrile, benzaldehyde and N,N-dimethylaniline using aluminium doped CdSeS/CdZnSeS(Al)/ZnS quantum dots (QDs) as visible light catalysts to synthesize α-aminobutyrilitriles at room temperature and under mild conditions. The reactions exhibit high functional group tolerance, and the well dispersed quantum dot catalysts are highly efficient with a turnover number (TON) greater than 1.1 × 103 and can be recycled at least three times without significant loss of catalytic activity.

Photocatalytic Synthesis of Sulfinamides and Sulfoxides from Nitroarenes and Thiophenols.

We present an efficient and versatile visible light-driven methodology for synthesizing sulfinamides and sulfoxides using nitroarenes as the nitrogen source and thiophenols as the sulfur source. The switch-over of the two reaction pathways was achieved by changing the type of photocatalyst and the amount of thiophenol in the reaction mixture. The reaction proceeds under mild conditions with good functional group tolerance and can easily be scaled up.

A rechargeable aqueous proton battery based on a dipyridophenazine anode and an indium hexacyanoferrate cathode.

A rocking-chair aqueous proton battery is assembled by using dipyridophenazine and indium hexacyanoferrate as the anode and cathode materials, respectively. The reversible amination of redox-active phenazine moieties in dipyridophenazine and fast intercalation-deintercalation of protons in hexacyanoferrate enable the aqueous proton battery to achieve a reversible specific capacity of 37 mA h g-1 at 1 A g-1, good cycling stability with 76.1% capacity retention over 3000 cycles and excellent rate capability.

Visible Light Induced Reduction and Pinacol Coupling of Aldehydes and Ketones Catalyzed by Core/Shell Quantum Dots.

We present an efficient and versatile visible light-driven methodology to transform aryl aldehydes and ketones chemoselectively either to alcohols or to pinacol products with CdSe/CdS core/shell quantum dots as photocatalysts. Thiophenols were used as proton and hydrogen atom donors and as hole traps for the excited quantum dots (QDs) in these reactions. The two products can be switched from one to the other simply by changing the amount of thiophenol in the reaction system. The core/shell QD catalysts are highly efficient with a turn over number (TON) larger than 4 × 104 and 4 × 105 for the reduction to alcohol and pinacol formation, respectively, and are very stable so that they can be recycled for at least 10 times in the reactions without significant loss of catalytic activity. The additional advantages of this method include good functional group tolerance, mild reaction conditions, the allowance of selectively reducing aldehydes in the presence of ketones, and easiness for large scale reactions. Reaction mechanisms were studied by quenching experiments and a radical capture experiment, and the reasons for the switchover of the reaction pathways upon the change of reaction conditions are provided.

Visible-Light Photocatalytic Synthesis of Amines from Imines via Transfer Hydrogenation Using Quantum Dots as Catalysts.

CdSe/CdS core/shell quantum dots (QDs) can be used as stable and highly active photoredox catalysts for efficient transfer hydrogenation of imines to amines with thiophenol as a hydrogen atom donor. This reaction proceeds via a proton-coupled electron transfer (PCET) from the QDs conduction band to the protonated imine followed by hydrogen atom transfer from the thiophenol to the α-aminoalkyl radical. This precious metal free transformation is easy to scale up and can be carried out by a one-pot protocol directly from aldehyde, amine, and thiophenol.  Additional advantageous features of this protocol include a wide substrate scope, high yield of the amine products, extremely low catalyst loading (0.001 mol %), high turnover number (105), and the mild reaction conditions of using visible light or sun light at room temperature in neutral media.

Visible-light mediated directed perfluoroalkylation of hydrazones.

Perfluoroalkylation of N-alkylhydrazones has been achieved via visible light mediated photoredox reactions between the hydrazone and perfluoroalkyl iodide (RfI). This protocol provides a convenient and efficient access to a series of perfluoroalkylated aromatic aldehyde hydrazones which tolerates a wide range of functional groups on the aromatic ring, and allows the use different types of primary and secondary perfluoroalkyl iodides with up to eight carbon atoms. Furthermore, aliphatic aldehyde hydrazones and N-monosubstituted hydrazones which are unreactive in previously reported hydrazone perfluoroalkylation reactions now take part in the reaction under our reaction conditions to give a satisfactory yield of products. Stern-Volmer quenching studies and spin-trapping experiments indicated that these reactions proceed by free radical addition of the Rf radical to the azomethine atom followed by one electron oxidation of the hydrazyl radical and deprotonation of the diazenium cation.

Visible light mediated cyclization of tertiary anilines with maleimides using nickel(II) oxide surface-modified titanium dioxide catalyst.

Surface-modified titanium dioxides by highly dispersed NiO particles have an extended absorption in the visible light region and a reduced hole-electron pair recombination than unmodified TiO2. They have now been successfully applied as highly active heterogeneous photocatalysts in the visible light mediated direct cyclization of tertiary anilines with maleimides to give tetrahydroquinoline products in moderate to high yields at ambient temperature. In contrast with unmodified titanium dioxide catalysts that are conventionally used in a stoichiometric amount in combination with UVA light, only a catalytic amount (1 mol %) of the surface-modified TiO2 catalyst is needed along with visible light to efficiently catalyze the reaction. Compared with transition-metal complexes such as Ru(bpy)3Cl2 or Ir(ppy)2(dtbbpy)PF6, advantages of these surface-modified titanium dioxides as photocatalyst include high catalytic activity, low cost, ease of recovering, and being able to be used for at least nine times without significant decay of catalytic activity.

Synthesis and antimicrobial activities of oxazepine and oxazocine derivatives.

A series of annulated 7-membered oxazepine and 8-membered oxazocine derivatives were synthesized by photoreaction of phthalimide derivatives and an alkene. The antimicrobial activities of the synthesized compounds were evaluated, and compounds 18 and 20 exhibited best antibacterial activity against Gram-positive bacteria. The relationships between structure (especially steric structure) and antimicrobial activities are discussed.

A three-component reaction by photoinduced electron transfer mechanism with N-protected pyrroles as neutral carbon nucleophiles.

A new photoinduced three-component reaction between a cyanoarene, an alkene and an N-protected pyrrole has been developed. This reaction extended the scope of the photo-NOCAS reaction by introducing pyrrole as a neutral carbon-centered nucleophile. The cyanoarenes used include tetracyanobenzene (TCB), 2,3,5,6-tetrafluoro-1,4-dicyanobenzene (TFDCB) and 1,4-dicyanobenzene (DCB). N-Methyl, N-phenyl and N-Boc pyrroles are suitable nucleophiles in the reaction. Taking advantage of the strong electron acceptor ability of the singlet excited TCB, a wide range of alkenes, including the highly electron deficient 4-fluoro-, 4-chloro-, 2,3,4,5,6-pentafluorostyrenes and N-methylmaleimide take part in this reaction, leading to the simultaneous 1,2-diarylation of the alkene and the regioselective 2-alkylation of the pyrrole ring via sequential formation of two new C-C bonds between the three reactants.

Directly measured activation parameters for the ring expansions of cyclopropylhalocarbenes.

Activation parameters have been redetermined for the ring expansions of cyclopropylchlorocarbene and cyclopropylfluorocarbene; agreement between the experimental and computed activation parameters has been significantly improved.

An efficient and chemoselective procedure for acylal synthesis.

A novel heterogeneous efficient procedure has been developed for the chemoselective synthesis of acylals (1,1-diacetates) under solvent-free conditions. A novel catalyst prepared by the sulfuric acid catalyzed copolymerization of p-toluenesulfonic acid and paraformaldehyde displays extremely high activities for the title reactions, affording average yields over 90% within several minutes. A comparative study showed that the novel catalyst has much higher activity than other catalysts used for this purpose. Besides, the novel catalyst displays chemoselectivity for the protection of aldehydes in the presence of ketones. In addition the high acidity (4.0 mmol/g), thermal stability (200 ºC) and easy reusability make the novel catalyst one of the best choices for the process.

Regioselective synthesis of 3-acylindolizines and benzo- analogues via 1,3-dipolar cycloadditions of N-ylides with maleic anhydride.

3-Acylindolizines (5a-5f) and their benzo- analogues 1-acylpyrrolo[1,2-a]quinolines (6a-6f) and 1-acylpyrrolo[2,1-a]isoquinolines (7a-7i) are regioselectively synthesized by a convenient one pot reaction of the corresponding pyridinium (quinolinium, isoquinolinium) ylide with maleic anhydride (MA) in the presence of the mild oxidant tetrakispyridinecobalt(ii) dichromate (TPCD). These reactions proceed via a tandem reaction sequence of 1,3-dipolar cycloaddition of azomethine ylide with MA, anhydride hydrolysis and oxidative bisdecarboxylation of the primary cycloadducts followed by dehydrogenative aromatization of the dihydroindolizines. TPCD serves as both decarboxylation and dehydrogenation reagent in the reactions. These results show that TPCD is a promising new reagent for bisdecarboxylation of aliphatic carboxylates.

Synthesis and antiproliferative activity of indolizine derivatives incorporating a cyclopropylcarbonyl group against Hep-G2 cancer cell line.

Indolizine and annulated indolizine derivatives incorporating a cyclopropylcarbonyl group were synthesized in a one pot procedure by the tanden reactions of [3+2] cycloaddition of the corresponding N-ylide with electron deficient alkene. Seventeen indolizine derivatives were reported for the first time. All the compounds were examined for their antiproliferative activity against the human hepatocellular liver carcinoma (Hep-G2) cell line by MTT method. Among the compounds tested, 5a, 5d, 5 g and 5 j showed the most favorable activities with IC(50) values of 0.39, 0.48, 0.29 and 0.20 microg/mL. Especially, compound 5 j displayed potent antiproliferative activities with IC(50) value of 0.20 microg/mL, and showed significant EGFR kinase inhibitory activity with IC(50) value of 0.085 microM. Docking simulations of 5 j were carried out to illustrate the binding mode of the molecular into the EGFR active site.

Intermolecular photocyclizations of N-(omega-hydroxyalkyl)tetrachlorophthalimide with alkenes leading to medium- and large-ring heterocycles--reaction modes and regio- and stereoselectivity of the 1,n-biradicals.

A new photocyclization strategy by using intermolecular tandem reactions between N-(omega-hydroxyalkyl)-4,5,6,7-tetrachlorophthalimides (1, 2, and 3) and a series of acyclic and cyclic alkenes is reported. Electron transfer of the triplet-excited phthalimide with the alkene and regioselective trapping of the alkene cation radical by the hydroxyl group at the phthalimide side chain gives a triplet 1,n-biradical, which after intersystem crossing (ISC) leads to regio- and diastereoselective synthesis of polycyclic heterocycles with an N,O-containing medium to large ring. Regio- and diastereoselectivity in the cyclizations are clarified by unambiguous steric structure assignments of the products by X-ray diffraction or extensive 2D NMR measurements. The diastereoselectivity is decided by the stereochemical course of the ISC process of the triplet 1,n-biradicals. These intermolecular photoreactions also furnish a new strategy to generate triplet 1,n-biradicals. Therefore, in photoreactions of 1 and 2 with phenylcyclohexene, the unprecedented stereoselective formation of products by intramolecular hydrogen-atom transfer in the 1,n-biradical intermediate was found (9 and 23). These facts provide direct verification to the reaction pathways of the 1,n-biradicals and give a new insight into the factors deciding reaction-pathway partitioning and stereoselectivity.

Surface modification with BSA blocking based on in situ synthesized gold nanoparticles in poly(dimethylsiloxane) microchip.

A stable BSA blocking poly(dimethylsiloxane) (PDMS) microchannel was prepared based on in situ synthesized PDMS-gold nanoparticles composite films. The modified microchip could successfully suppress protein adsorption. The assembly was followed by contact angle, charge-coupled device (CCD) imaging, electroosmotic flow (EOF) measurements and electrophoretic separation methods. Contact angle measurements revealed the coated surface was hydrophilic, water contact angle for coated chips was 45.2 degrees compared to a water contact angle for native PDMS chips of 88.5 degrees. The coated microchips exhibited reproducible and stable EOF behavior. With FITC-labeled myoglobin incubation in the coated channel, no fluorescence was observed with CCD image, and the protein exhibited good electrophoretic effect in the modified microchip.

{6,6'-Dieth-oxy-2,2'-[ethane-1,2-diylbis(nitrilo-methyl-idyne)]diphenolato}zinc(II) monohydrate.

The mol-ecule of the title compound, [Zn(C(20)H(22)N(2)O(4))]·H(2)O, deviates from planarity with a dihedral angle between the two benzene rings is 18.3 (1)°. The four-coordinate Zn(II) ion has a distorted square-planar coordination and is N(2)O(2)-chelated by the Schiff base ligand. The Zn(II) ion and solvent water mol-ecule are located on a twofold rotation axis. The structure displays inter-molecular O-H⋯O hydrogen bonding.

Aqua-(dicyanamido)-{µ-6,6'-dimeth-oxy-2,2'-[ethane-1,2-diylbis(nitrilo-methyl-i-dyne)]diphenolato}copper(II)sodium(I).

The mol-ecule of the title compound, [CuNa(C(18)H(18)N(2)O(4))(C(2)N(3))(H(2)O)], is almost planar, the maximum deviation from the mol-ecular plane being 0.48 (4) Å. The coordination environment of the Cu(2+) ion is distorted square-planar and it is N(2)O(2)-chelated by the Schiff base ligand. The Na(+) cation has a distorted octahedral environment defined by the four O atoms of the 6,6'-dimeth-oxy-2,2'-[ethane-1,2-diylbis(nitrilo-methyl-idyne)]diphenolate ligand, a water ligand and a dicyanamide anion.

Aqua-(dicyanamido){µ-6,6'-dimeth-oxy-2,2'-[ethane-1,2-diylbis(nitrilo-methyl-idyne)]diphenolato}nickel(II)sodium.

The mol-ecule of the title compound, [NaNi(C(18)H(18)N(2)O(4))(C(2)N(3))(H(2)O)], is approximately planar, with a maximum deviation from the mol-ecular plane of 0.770 (5) Å. The coordination environment of the Ni(2+) ion is distorted square-planar and it is N(2)O(2) coordinated by the 6,6'-dimeth-oxy-2,2'-[ethane-1,2-diylbis(nitrilo-methyl-idyne)]diphenolate Schiff base ligand. The Na(+) atom is chelated by the four O atoms of the Schiff base ligand, a water ligand and a dicyanamide anion. The structure displays inter-molecular O-H⋯N hydrogen bonding.