The Oxidation of Alcohols in N-Oxyl-Immobilized Silica Gel/Aqueous NaOCl Disperse Systems. A Prominent Access to a Column-Flow System

Abstract

The oxidation of alcohols was performed successfully in a disperse system with N-oxyl-adsorbed or immobilized silica gel as a disperse phase and aqueous NaOCl as a disperse medium. In the disperse system, the oxidation of sec-alcohols afforded the corresponding ketones, while prim-alcohols were oxidized to aldehydes and/or carboxylic acids depending on their structures and reaction conditions. The N-oxyl-immobilized silica gel was recovered and repeatedly used without a significant change in the product yields. A column-flow system was also investigated for the oxidation of alcohols by use of a newly devised column packed with the N-oxyl-immobilized silica gel.

On the Use of Polyelectrolytes and Polymediators in Organic Electrosynthesis

“…In fact, halide salts are needed as co-mediators for the activation of the solid-supported mediator units. [7][8][9] Compared to the dispersed-phase strategy,the attachment of am ediator and/or supporting electrolyte to soluble polymer backbones (polymediators and polyelectrolytes) to create ah omogeneous electrolyte represents ap romising approach for improving both the ionic conductivity and electron transfer kinetics.T od ate,t his has only been attempted by Steckhan and co-workers,w ho tested ap olymer-supported triarylamine for the oxidation of anisyl alcohol. [10] While in principle,t he polymediator was active, the system still suffered from poor electron transfer kinetics and complete degradation of the soluble polymer during the electrolysis.T his study prompted us to investigate the requirements for the successful use of soluble polymers in electrosynthesis,a nd to develop am ore robust and active system that allows for practical current densities and repeated use.H erein, we report the first method for the selective electrooxidation of alcohols to carbonyl compounds using recyclable polyelectrolytes and polymediators in combination with membrane separation processes for polymer recovery (see Scheme 1).With respect to the redox-active unit, we selected 2,2,6,6tetramethylpiperidin-1-oxyl (TEMPO), ar obust, versatile, and well-characterized mediator for homogeneously catalyzed electrochemical transformations.…”

Electroorganic synthesis in oil-in-water (O/W) nanoemulsion: TEMPO-mediated electrooxidation of amphiphilic alcohols in water

“…The combined extracts were dried (Na 2 SO 4 ), filtered, and concentrated under reduced pressure. The residue was purified by column chromatography (SiO 2 , Hexane/ AcOEt¼1/1) to give the desired 3-phenyl-1,2-propanediol (3g, 1.38 mg, 9.1 mmol, 91%) as a colorless liquid: 31 4.14. Preparation of 4-(6-bromohexanoylamino)-2,2,6,6-tetramethylpiperidine-1-oxyl (1g) 17a Into a 50 mL two-necked round-bottomed flask equipped with a magnetic stirring bar, a three-way cock, and a rubber septum was placed 6-bromohexanoic acid (720 mg, 3.7 mmol), and the flask was purged with argon.…”

Efficient and Eco-Friendly Preparation of 4-Methyl-5-formyl-thiazole

“…The formation of the aldehyde group in this substance has been the focus of much research. Recently developed methods include the oxidation of 4-methyl-5-(2-hydroxyethyl)thiazole or 4-methyl-5-(hydroxymethyl)thiazole with MnO 2 , CrO 3 , or NaOCl [4,5,6,7] and the reduction of carboxylic ester with LiAlH 4 , NaBH 4 , or Red-Al [4,8,9,10]. However, these methods are eco-unfriendly and too expensive for industrial production.…”