Copper Oxide Nanoparticles

Biographical Sketches

Atefeh Shamsian was born in Hamedan (Iran) in 1984. She completed her B.Sc. in chemistry in 2007 from the Bu-Ali Sina University and her M.Sc. degree in organic chemistry from the same university under the guidance of Prof. M. A. Zolfigol in 2009. She is currently working as a Ph.D. student in organic chemistry under the supervision of Prof. D. Habibi. Her research interest is focused on the application of heterogeneous catalysts in the synthesis of ­heterocyclic compounds.

Introduction

<P>Generally, nanoscale heterogeneous catalysts offer higher surface area and low-coordinated sites, which are responsible for the higher catalytic activity. [¹] Particularly, in recent years the application of copper oxide nanoparticles for organic reactions has attracted immense attention.</P><P>Indeed, the copper nanoparticle catalyzed reactions provide the advantages of high atom efficiency, simplified isolation of product, and easy recovery and recyclability of the catalyst. [²-4] This catalyst appears as one of the most promising solutions toward efficient reactions under mild and environmentally benign conditions in the context of green chemistry.</P>

Preparation

<P>Copper acetate and acetic acid were dissolved in distilled water and the solution was heated to 100 ˚C before NaOH was added rapidly. After being cooled to room temperature, black powder precipitates were separated by centri­fugation, then washed several times with distilled water and ethanol and dried. [5] [6] </P><P>The synthesized nanoparticles were characterized by XRD, SEM, TEM, and PL spectrometry.</P>

Abstracts

<TD VALIGN="TOP"> (A) Cross-Coupling of Thiols: This reaction is the first example of the use of CuO nanoparticles for the catalysis of C-S cross-coupling. The reactions of aryl and alkyl thiols with iodobenzene are effective in the presence of KOH under nitrogen atmosphere. [7] </TD><TD VALIGN="TOP">

</TD><TD VALIGN="TOP"> (B) Asymmetric Aldol Reactions: Kantam and co-workers have reported a new efficient method for the direct asymmetric aldol reactions of aromatic and heteroaromatic aldehydes with acetone to afford chiral β-hydroxy carbonyl compounds in good yields and excellent to moderate enantioselectivities using nanocrystalline copper(II) oxide in the presence of (1S,2S)-(-)-1,2-diphenylethylenediamine. [8] </TD><TD VALIGN="TOP">

</TD><TD VALIGN="TOP"> (C) Alkyne-Azid Cycloaddition: CuO nanoparticles catalyzed the reaction of azide and alkynes as a representative example of click chemistry. In the absence of reductants they show good catalytic activity to form 1,4-disubstituted 1,2,3-triazols even in THF as well as in water. [9] [¹0] </TD><TD VALIGN="TOP">

</TD><TD VALIGN="TOP"> (D) Synthesis of Aryl Selenides: A new, efficient, and ligand-free cross-coupling of aryl halides and diaryl diselenides using a catalytic amount of nanocrystalline CuO as a recyclable catalyst with KOH as base is reported. [²] </TD><TD VALIGN="TOP">

</TD><TD VALIGN="TOP"> (E) Synthesis of Propargylamines: Kantam and co-workers reported an efficient three-component coupling of aldehydes, amines, and alkynes to prepare propargylamines in nearly quantitative yields using nano-crystalline CuO. The reaction does not require any co-catalyst. [¹¹] </TD><TD VALIGN="TOP">

</TD><TD VALIGN="TOP"> (F) Aza-Michael Reaction: Nanocrystalline copper(II) oxide efficiently catalyzed the conjugate addition of aliphatic amines to α,β-unsaturated compounds to produce β-amino compounds with excellent yields under mild reaction conditions. Similarly, glycine esters are obtained in good yields by insertion of α-diazoacetate into N-H bonds of amines. The catalyst is used in three cycles with minimal loss of activity. [¹²] </TD><TD VALIGN="TOP">

</TD><TD VALIGN="TOP"> (G) Vinylation of Imidazoles: Rama Rao and co-workers reported that recyclable copper oxide nanoparticles catalyzed most efficiently and straightforward the vinylation of imidazoles with vinyl halides under ligand-free conditions. Utilizing this protocol, various imidazoles were cross-coupled with different substituted vinyl halides to obtain the corresponding products in excellent yields while retaining the configuration. [¹³] </TD><TD VALIGN="TOP">

</TD><TD VALIGN="TOP"> (H) Cross-Coupling of Diselenides with Aryl Boronic Acids: This general cross-coupling was performed with organic diselenides and aryl boronic acids bearing electron-withdrawing and -donating groups affording the corresponding selenides in good to excellent yields. The CuO nanoparticles can be easily recovered and utilized for further catalytic reactions. [¹4] </TD><TD VALIGN="TOP">

</TD><TD VALIGN="TOP"> (I) C-N Cross Coupling of Amines: CuO nanoparticles catalyze the C-N cross-coupling of amines with iodobenzene in excellent yields. The reaction is simple and efficient and operates under air with ligand-free conditions. The catalyst is ­recyclable without loss of activity. [4] </TD><TD VALIGN="TOP">

</TD>

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