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Novel acyl pyrazoles and acyl triazoles have been prepared by means of the oxidative amidation of aldehydes in the presence of the requisite azole. Yields range from modest to good in both cases, and some limitations of the substrate scope have been discovered. Acyl pyrazoles were prepared by treatment of a mixture of aldehyde and pyrazole with an oxoammonium salt bearing the nitrate anion. In the case of acyl triazoles, the oxidative functionalization was performed using sodium persulfate as a terminal oxidant in the presence of a catalytic quantity of a nitroxide.

The [1,2,4]triazolo[4,3-a]pyridine derivative 3-(4-(benzyloxy)-3-methoxyphenyl)-[1,2,4]triazolo[4,3-a]pyridine was prepared in a 73% isolated yield by means of an oxidative ring closure of a hydrazine intermediate. Sodium hypochlorite was used as the oxidant and ethanol as a solvent, making the process a clean, green approach. The reaction was performed at room temperature for 3 h, and then the heterocycle was isolated in an analytically pure form by extraction, followed by passing the crude product mixture through a small plug of alumina. [ABSTRACT FROM AUTHOR]

The acyl pyrazole derivative (3,5-di-tert-butylphenyl)(1H-pyrazol-1-yl)methanone was prepared simply and rapidly in 86% isolated yield by means of an oxidative functionalization reaction of an aldehyde with pyrazole. A substoichiometric quantity of 4-acetamido-2,2,6,6-tetramethylpiperidine-1-oxoammonium nitrate was used as the oxidant. The reaction was performed solvent-free and in the absence of a base, making it a clean, green approach. The mixture of aldehyde, pyrazole, and the oxidant was heated at 55 °C for 3 h, and then, the product was isolated in analytically pure form via extraction with no need for column chromatography. [ABSTRACT FROM AUTHOR]

A methodology for the oxidative amidation of aldehydes to yield N‐acyl azoles is reported. The approach employs sodium persulfate and a catalytic amount of a nitroxide and is applicable to a range of structurally diverse substrates. [ABSTRACT FROM AUTHOR]

Background: Oxidation is a valuable tool in preparative organic chemistry. Oxoammonium salts and nitroxides have proven valuable as reagents and catalysts in this endeavor., Objective: The objective of this study is to scale up the oxidative amidation, ester formation, and nitrile formation using nitroxide as an organocatalyst., Methods: Oxidative functionalization reactions were scaled from the 1 mmol to the 1 mole level. Sodium persulfate was used as the primary oxidant, and a nitroxide was employed as a catalyst. The products of the reactions were isolated in analytically pure form by extraction with no need for column chromatography., Results: The oxidative amidation and esterification of aldehydes can be scaled up from 1 mmol to 1 mole effectively, with comparable product yields being obtained at each increment. This work shows that conditions developed on a small scale can be transferred to a larger scale without reoptimization. The oxidative functionalization of aldehydes to prepare nitriles is not amenable to direct scale-up due to the concomitant formation of significant quantities of the corresponding carboxylic acid, thereby compromising the product yield., Conclusion: Two of the three oxidative transformations studied here can be scaled up successfully from the 1 mmol to the 1 mole level., (Copyright© Bentham Science Publishers; For any queries, please email at epub@benthamscience.net.)