Electrochemical synthesis of 5,6-dihydroxy-2-methyl-1-benzofuran-3-carboxylate derivatives

Electrochemical oxidation of catechols (1a-c) has been studied in the presence of methyl acetoacetate (2a) and ethyl acetoacetate (2b) as nucleophiles in aqueous solution using cyclic voltammetry and controlled-potential coulometry. The results indicate that the quinones derived from catechols (1a-c) participate in Michael addition reactions with 2a and 2b to form the corresponding benzofuran derivatives (3a-f). The electrochemical synthesis of 3a-f has been successfully performed in an undivided cell in good yield and purity. The oxidation mechanism was deduced from voltammetric data and by coulometry at controlled potential. The products have been characterized after purification by IR, ¹H NMR, ¹³C NMR, MS, and single crystal X-ray diffraction.     

An efficient electrochemical synthesis of diamino-o-benzoquinone: mechanistic and kinetic evaluation of the reaction of azide ion with o-benzoquinone

An efficient method for the synthesis of diamino-o-benzoquinone based on the Michael reaction of electrochemically generated o-benzoquinone with azide ion is described, as well as an estimation of the homogeneous rate constant (k(obs)) of the reaction of o-benzoquinone with azide ion by the digital-simulation method.     

One-pot synthesis of highly conjugated benzofuran derivatives based on electrochemical oxidation of benzenediols in the presence of dibenzoylmethane

Electrochemical oxidation of benzenediols (1--4) has been studied in the presence of dibenzoylmethane (5) as a nucleophile using cyclic voltammetry and controlled-potential coulometry. The results indicate that the electrochemically generated quinones participate in Michael addition reaction with 5 via various mechanisms to produce new benzofuran derivatives. We derived various products based on electrochemical oxidation in the controlled potential condition, at carbon electrode without toxic reagents in an undivided cell and ambient condition.     

A Facile Room Temperature Synthesis of Zinc Oxide Nanostructure and Its Influence on the Flame Retardancy of Poly Vinyl Alcohol

In this work, poly vinyl alcohol–ZnO nanocomposites were synthesized via two different in situ and ex-situ methods. In ex-situ, at first zinc oxide nanostructures were synthesized by one-step precipitation reaction between zinc acetate and sodium hydroxide. The effect of different surfactants such as poly vinyl pyrrolidone, poly vinyl alcohol and poly ethylene glycol on the morphology of ZnO nanostructures was investigated. Nanostructures were characterized by X-ray diffraction, scanning electron microscopy. The influence of ZnO nanostructures on the flame retardancy of the poly vinyl alcohol matrix was studied using underwriter laboratories UL-94 analysis.     

Damped vibration of a graphene sheet using a higher-order nonlocal strain-gradient Kirchhoff plate model

A higher-order nonlocal strain-gradient model is presented for the damped vibration analysis of single-layer graphene sheets (SLGSs) in hygrothermal environment. Based on Kirchhoff plate theory in conjunction with a higher-order (bi-Helmholtz) nonlocal strain gradient theory, the equations of motion are obtained using Hamilton's principle. The higher-order nonlocal strain gradient theory has lower- and higher-order nonlocal parameters and a material characteristic parameter. The presented model can reasonably interpret the softening effects of the SLGS, and indicates a reasonably good match with the experimental flexural frequencies. Finally, the roles of viscous and structural damping coefficients, small-scale parameters, hygrothermal environment and elastic foundation on the vibrational responses of SLGSs are studied in detail.     

Investigation of electrochemically induced Michael addition reactions. Oxidation of some dihydroxybenzene derivatives in the presence of azide ion

In aqueous solution containing azide ion as a nucleophile, electrochemical oxidation of hydroquinone and some dihydroxybenzoic acids have been studied using cyclic voltammetry and controlled-potential coulometry. The voltammetric data show that electrochemically generated para and ortho-benzoquinones participate in Michael addition reactions with azide ions to form the corresponding diazido or diaminobenzoquinones. In this work, we have proposed various mechanisms for the electrode process and we report an efficient and one-pot method for the synthesis of 2,5-diazido-1,4-benzoquinone, 2,5-diamino-1,4-benzoquinone, 4,5-diamino-1,2-benzoquinone, and 2,3-diamino-5,6-dioxocyclohexa-1,3-dienecarboxylic acid based on the Michael reaction of electrochemically generated ortho and para-benzoquinones with azide ion in an undivided cell using an environmentally friendly reagent-less method in ambient conditions. An estimation of the observed homogeneous rate constant (k_obs) of the reaction of electrochemically generated para-benzoquinone with azide ion by the digital simulation method is also presented.