Facile open air oxidation of benzylic alcohols in distilled water by in situ made copper(II) complexes

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• 作者：Jahir Uddin Ahmad ; Minna T. R&auml ; is&auml ; nen ; Marianna Kemell ; Mikko J. Heikkil&auml ; Markku Leskel&auml ; Timo Repo ; ^{timo.repo@helsinki.fi}
• 关键词：Oxidation ; Alcohols ; Copper ; Open air ; Distilled water
• 刊名：Applied Catalysis A: General
• 出版年：2012
• 出版时间：27 December, 2012
• 年：2012
• 卷：449
• 期：Complete
• 页码：153-162
• 全文大小：2484 K

文摘

A highly efficient, selective and green catalytic protocol for open air oxidation of primary benzylic alcohols into aldehydes by in situ made N-isopropyl-3,5-di-tert-butylsalicylaldimine (HL3)-Cu(II) complexes and TEMPO (2,2,6,6-tetramethyl-piperidinyloxyl radical) is introduced herein. Distilled water as a solvent the reaction proceeds at 80 ¡ãC temperature without any auxiliarities such as base and/or co-solvent. For example, benzyl alcohol is quantitatively and selectively oxidized to benzaldehyde within a few hours under optimized reaction conditions [80 ¡ãC, open air, 0.3 mol % CuBr₂, 2 mol % HL3, 3 mol % TEMPO and 5 mL of distilled water]. Under anaerobic conditions, the catalyst decomposes to a free ligand and Cu₂O nanoparticles (diameter >50 nm) via anticipated Cu(I)-hydroxo complex. On the basis of these observations and deuteration studies, a plausible reaction mechanism is proposed for the catalytic system.