Under visible-light irradiation, the gold-catalyzed intermolecular difunctionalization of alkynes with aryl diazonium salts in methanol affords a variety of α-aryl ketones in moderate to good yields. In contrast to previous reports on gold-catalyzed reactions that involve redox cycles, no external oxidants or photosensitizers are required. The reaction proceeds smoothly under mild reaction conditions and shows broad functional-group tolerance. Further applications of this method demonstrate the general applicability of the arylation of a vinyl gold intermediate instead of the commonly used protodemetalation step. This step provides facile access to functionalized products in one-pot processes. With a P,N-bidentate ligand, a stable aryl gold(III) species was obtained, which constitutes the first direct experimental evidence for the commonly postulated direct oxidative addition of an aryl diazonium salt to a pyridine phosphine gold(I) complex.

Photosensitizer-Free Visible-Light-Mediated Gold-Catalyzed 1,2-Difunctionalization of Alkynes

The direct arylation of heteroaromatics with an easily accessible and recyclable, heterogeneous TiO2 catalyst and visible light was developed. Electron-rich as well as electron-poor heteroarenes could be applied in this transformation, and the corresponding products were isolated in very good yields. Azoethers were detected as reactive intermediates, and the unexpected role of TiO2 in their formation as well as reaction was established.

Unexpected Dual Role of Titanium Dioxide in the Visible Light Heterogeneous Catalyzed C–H Arylation of Heteroarenes

Azo-group-containing polymers for use in communications technologies

Gold‐katalysierte 1,2‐Difunktionalisierung von Alkinen mit sichtbarem Licht ohne zusätzlichen Photosensibilisator

Azo coupling reactions structures and mechanisms

Aryldiazophenyl sulfides prepared from diazotised arylamines and thiophenol at controlled pH, are coupled with β-naphthol yielding the corresponding azo dye.



A kinetic study of the diazo coupling reaction of p-nitrobenzenediazo phenyl sulfide with β-naphthol under various conditions revealed that the reaction is of first order kinetics with respect to the diazo phenyl sulfide, and that the rate of coupling measured colorimetrically is influenced by the hydrogen ion concentration and by the ionising power of the medium.

Preparation of Diazo Phenyl Sulfides. Kinetics and Mechanism of the Diazo Coupling Reaction of p-Nitrobenzenediazo Phenyl Sulfide with β-Naphthol under Various Conditions

Rate data are presented for the diazo coupling reaction of arenediazo methyl ethers with β-naphthol in solutions of dioxane, ethanol, and propan-2-ol acidified with hydrochloric acid at 25°C. Over the range of HCl concentrations studied, pseudo-first-order rate constants were obtained and the reaction was found to be of first order in diazo ether. The relationship between the observed rate constants (kobs.) and hydrochloric acid concentration (cHCl) was found to be non-linear. Correlations of reaction rates with the Hammett acidity function (H0) and with the Hammett substituent constant (σx) conform with a mechanism in which the slow step is unimolecular decomposition of the protonated diazo ether, DEH+, to the coupling entity, the diazonium ion, D+, which instantly reacts with β-naphthol to give the azo dye.

Kinetics and mechanism of the diazo coupling reaction of arenediazo methyl ethers with β-naphthol. Part 1. The rates of reaction in nonaqueous acid solutions

Preparation of diazo phenyl sulfides, kinetics and mechanism of the diazo coupling reaction of p-nitrobenzenediazo phenyl sulfide with beta-naphthol under various conditions

Nabil Khalil Masoud

Papers

Preparation of Diazo Phenyl Sulfides. Kinetics and Mechanism of the Diazo Coupling Reaction of p-Nitrobenzenediazo Phenyl Sulfide with β-Naphthol under Various Conditions

Kinetics and mechanism of the diazo coupling reaction of arenediazo methyl ethers with β-naphthol. Part 1. The rates of reaction in nonaqueous acid solutions

Preparation of diazo phenyl sulfides, kinetics and mechanism of the diazo coupling reaction of p-nitrobenzenediazo phenyl sulfide with beta-naphthol under various conditions