TEMPO and Carboxylic Acid Functionalized Imidazolium Salts/Sodium Nitrite: An Efficient, Reusable, Transition Metal‐Free Catalytic System for Aerobic Oxidation of Alcohols

Abstract

An effective catalytic system comprising a 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) func-, and sodium nitrite (NaNO 2 ) was developed for the aerobic oxidation of aliphatic, allylic, heterocyclic and benzylic alcohols to the respective carbonyl compounds with excellent selectivity up to > 99%, even at ambient conditions. Notably, the catalyst system could preferentially oxidize a primary alcohol to the aldehyde rather than a secondary alcohol to the ketone. Moreover, the reaction rate is greatly enhanced when a proper amount of water is present. And a high turnover number (TON 5000) is achieved in the present transition metal-free aerobic catalytic system. Additionally, the functionalized imidazolium salts are successfully reused at least four times. This process thus represents a greener pathway for the aerobic oxidation of alcohols into carbonyl compounds by using the present task-specific ionic liquids in place of the toxic and volatile additive, such as hydrogen bromide, bromine, or hydrogen chloride (HBr, Br 2 or HCl), which is commonly required for the transition metal-free aerobic oxidation of alcohols.

Chloropalladation Triggering the Cascade Annulation to Construct Functionalized Saturatedγ-Lactones in Ionic Liquids

“…离子液体作为 新兴的绿色化学溶剂, 反应可在均相催化反应体系中进 行, 对水和空气稳定, 便于反应操作和处理, 易回收, 有望解决化学反应过程中出现的污染问题 [17] . ( 1) 1 结果与讨论 [22] , [C 2 OHmim]Cl [23] , [C 2 O 2 mim]Cl [24] )参考相应文 献合成.…”

Nitroxide: Anwendungen in der Synthese und in der Polymerchemie

“…[67] Zusammen mit TEMPO wurden häufig auch Über-gangsmetalle als Cokatalysatoren für aerobe Oxidationen von Alkoholen verwendet. [68,69] So fanden Cerammoniumnitrat (CAN), [70] [80] Grund-sätzlich laufen elektrochemische Alkoholoxidationen im Acetonitril/Wasser als Lösungsmittel auch in ungeteilten Zellen ab.…”

“…Nach erfolgter Reaktion gelang dank seines Imidazolium-Ankers die Zweiphasenextraktion aus Ether in eine ionische Flüssigkeit (ionic liquid, IL) und somit die Abtrennung vom Produkt, das in der organischen Phase verblieb. [67] Vor kurzem konnten wir zeigen, dass ein Polyamidoamin(PAMAM)-Dendrimer der fünften Generation zusammen mit Polyethylenoxid (PEO) elektroversponnen werden kann. Dabei resultieren PEO enthaltende Dendrimernanofasern.…”

Preparation, characterization and use of 1,3-disulfonic acid imidazolium hydrogen sulfate as an efficient, halogen-free and reusable ionic liquid catalyst for the trimethylsilyl protection of hydroxyl groups and deprotection of the obtained trimethylsilanes

“…Among them, Brönsted acidic ionic liquids have designed to replace solid acids and traditional mineral liquid acids like sulfuric acid and hydrochloric acid in chemical procedures [10][11][12][13][14]. Introduction of Brönsted-acidic functional groups into cations or anions of ionic liquids, especially SO 3 H and SO 4 H functional groups, obviously enhances their acidities and water solubility [15,16].…”