Graphene Oxide Promotes Site-Selective Allylic Alkylation of Thiophenes with Alcohols

The graphene oxide (GO) assisted allylic alkylation of thiophenes with alcohols is presented. Mild reaction conditions and a low GO loading enabled the isolation of a range of densely functionalized thienyl and bithienyl compounds in moderate to high yields (up to 90%). The cooperative action of the Bronsted acidity, epoxide moieties, and pi-surface of the 2D-promoter is highlighted as crucial in the reaction course of the present Friedel-Crafts-type protocol

A new copper(I) coordination polymer from 2,6-bis(1<i>H</i>-benzotriazol-1-ylmethyl)pyridine: Synthesis, characterization, and use as additive in transparent submicron UV filters

<p>The use of a new copper(I) coordination polymer (CP) as additive in transparent composite films of 190 nm of thickness for ultraviolet (UV) shielding is presented. The luminescent 1-D Cu(I) CP was easily synthesized through a self-assembly process between Cu(I) iodide and 2,6-bis(1<i>H</i>-benzotriazol-1-ylmethyl)pyridine (L). The CP, [Cu₂(<i>μ</i> − I)₂(<i>μ</i> − <b>L</b>)₂]_<i>n</i>, was structurally characterized by infrared, UV–visible diffuse reflectance and photoluminescence spectroscopy, elemental and thermogravimetric analyses, single-crystal and powder X-ray diffraction, and relativistic density functional theory calculations. The CP was dispersed and immobilized into a polymeric matrix in the presence of Sudan I, yielding a composite material that exhibits a reduction of 49% of the UV transmittance at 350 nm. Thus, the use of a new Cu(I) CP in polymeric composite films appears as a novel approach toward ultrathin and transparent UV shielding films, which have potential applications as protection layers of paints and coatings that tend to degrade when exposed to UV radiation.</p

[OSSO]-Type Iron(III) Complexes for the Low-Pressure Reaction of Carbon Dioxide with Epoxides: Catalytic Activity, Reaction Kinetics, and Computational Study

The selective conversion of variously substituted epoxides into the corresponding cyclic carbonates under mild reaction conditions was achieved with mononuclear Fe­(III) complexes bearing bis-thioether-diphenolate [OSSO]-type ligands, in combination with tetrabutylammonium bromide (TBAB). For example, propylene carbonate was obtained in 1 h at 35 °C (turnover frequency, TOF = 290 h^–1), from propylene oxide and 1 bar of CO₂ pressure, using 0.1 mol % of the Fe­(III) complex and 0.5 mol % of TBAB. Product divergence is observed only for cyclohexene oxide toward the exclusive formation of the aliphatic polycarbonate (TOF = 165 h^–1 at 80 °C and 1 bar of CO₂ pressure, using 0.1 mol % of the Fe­(III) complex and 0.1 mol % of tetrabutylammonium chloride). Kinetic investigations indicated reaction orders of two and one, with respect to the Fe­(III) complex, for the production of propylene carbonate and the poly­(cyclohexene carbonate), respectively. The enthalpy and entropy of activation were determined using the Eyring equation [for propylene carbonate: Δ<i>H</i>^‡ = 8.4 ± 0.7 kcal/mol and Δ<i>S</i>^‡ = −33 ± 3 cal/(mol·K); for poly­(cyclohexene carbonate): Δ<i>H</i>^‡ = 11.9 ± 0.3 kal/mol and Δ<i>S</i>^‡ = −36 ± 2.2 cal/(mol·K)]. Supported by density functional theory based investigations, we propose a mechanistic scenario in which the rate-limiting step is the bimetallic ring opening of the epoxide, in the case of propylene carbonate, and the monometallic insertion of the epoxide in the growing polymer chain, in the case of poly­(cyclohexene carbonate)