Continuous-flow synthesis of carboxylic acids from alcohols platinum and silicon dioxide-catalyzed hydrogen peroxide oxidation.

A continuous-flow method for the direct oxidation of alcohols to carboxylic acids is reported, employing hydrogen peroxide (HO) and a platinum (Pt) catalyst within a flow reactor system. This approach allows for precise control over the contact time between the reactants and the catalyst, enabling optimization of reaction conditions. By analyzing the yields of both aldehydes and carboxylic acids as a function of weight hourly space velocity (WHSV), selective synthesis of carboxylic acids was achieved without the formation of corresponding aldehydes.

Aluminium-catalysed synthesis of aryl enol ethers from phenols and dimethyl ketals.

We report an environmentally friendly, aluminium-catalysed, halide- and transition metal-free method for the synthesis of aryl enol ethers from phenols and dimethyl ketals that involves ketal exchange driven by the removal of methanol. The obtained aryl enol ethers were transformed into the corresponding diaryl ethers by Pd/C-catalysed dehydrogenation or DDQ oxidation.

Development of highly efficient Friedel-Crafts alkylations with alcohols using heterogeneous catalysts under continuous-flow conditions.

The development of Friedel-Crafts alkylations with alcohols under continuous-flow conditions using heterogeneous catalysts is reported. The reactivities and durabilities of the examined catalysts were systematically investigated, which showed that montmorillonite clay is the best catalyst for these reactions. A high turnover frequency of 9.

Wet and Dry Processes for the Selective Transformation of Phosphonates to Phosphonic Acids Catalyzed by Brønsted Acids.

A "wet" process and two "dry" processes for converting phosphonate esters to phosphonic acids catalyzed by a Brønsted acid have been developed. Thus, in the presence of water, a range of alkyl-, alkenyl-, and aryl-substituted phosphonates can be generally hydrolyzed to the corresponding phosphonic acids in good yields catalyzed by trifluoromethyl sulfonic acid (TfOH) at 140 °C (the wet process). On the other hand, with specific substituents of the phosphonate esters, the conversion to the corresponding phosphonic acids can be achieved under milder conditions in the absence of water (the dry process).

Nickel-catalyzed thioallylation of alkynes with allyl phenyl sulfides.

Allylic sulfides add to alkynes in the presence of nickel complexes efficiently to afford thio-1,4-dienes regio- and stereoselectively. Functional groups such as alkoxy, siloxy, hydroxy, carboalkoxy, chloro, and cyano groups are tolerated. A mechanism that involves a pi-allyl nickel intermediate is proposed on the basis of isolation of pi-allyl complexes and distribution of products in the reactions of alpha- or gamma-methylated allyl sulfide.

Rhodium-catalyzed nondecarbonylative addition reaction of ClCOCOOC2H5 to alkynes.

Addition of ethoxalyl chloride (ClCOCOOEt) to terminal alkynes at 60 degrees C in the presence of a rhodium(I)-phosphine complex catalyst chosen from a wide range affords 4-chloro-2-oxo-3-alkenoates regio- and stereoselectively. Functional groups such as chloro, cyano, alkoxy, siloxy, and hydroxy are tolerated. The oxidative addition of ethoxalyl chloride to [RhCl(CO)(PR(3))(2)] proceeds readily at 60 degrees C or room temperature and gives [RhCl(2)(COCOOEt)(CO)(PR(3))(2)] (PR(3) = PPh(2)Me, PPhMe(2), PMe(3)) complexes in high yields.