Abstract
In recent years, the synthesis of metal nanoparticles has attracted significant attention because of their unique properties. These nanoparticles are useful for diverse fields including catalysis, electronics, clinical diagnosis, etc. Although many strategies for the preparation of noble- and transition-metal nanoparticles have been published, the synthesis of indium nanoparticles (InNPs) has been scarcely reported. Some top-down methods involve the use of specific equipments and/or high temperatures, and most of the bottom-up methods require the use of indium salts and strong reducing agents such as sodium metal, zinc power, alkalides/electrides, or decomposition of organometallic complexes.1 Regrettably, some of them provide little control over particle size and size distribution, and generally it is mandatory the presence of stabilizing agents. On the other hand, the reducing systems based on the use of alkali-metals in combination with arenes in aprotic media, with the arene acting as electron carrier have received much attention. Some of us have been working on the preparation of transition metal nanoparticles by fast reduction of the corresponding metal chlorides with lithium and a catalytic amount of an arene [naphthalene, 4,4´-di-tert-butylbiphenyl (DTBB)].2 Herein, we report, a simple, mild, and efficient synthesis of very reactive, monodisperse (4.0 ± 1.5 nm) spherical InNPs, using indium(III) chloride in the presence of lithium powder and a catalytic amount of DTBB in THF at room temperature, and in the absence of any anti-agglomeration additive or ligand. Focusing on one of the most studied indium-mediated synthetic transformation, we decided to explore the above-mentioned InNPs-based system for the allylation of a variety of aldehydes and ketones in a one-pot procedure, by adding allyl bromide over a suspension of InNPs followed by the addition of the corresponding carbonyl compound. For most of the tested compounds, the homoallylic alcohol product was obtained in good yields. The InNPs were characterized by transmission electron microscopy (TEM) and UV-Visible spectroscopy. 1 Estager J., Nockemann P., Seddon K. R., Srinivasan G., y Swadźba-Kwaśny M. ChemSusChem 2012, 5, 117–124 and references therein. 2 F. Nador; L. Fortunato; Y. Moglie; C. Vitale and G. Radivoy Synthesis, 2009, 4027-4031 and references therein.
Highlights
In recent years, the synthesis of metal nanoparticles (NPs) has attracted significant attention because of their unique physical and chemical properties
It is known that the reactivity, reproducibility and the stereochemistry outcome of many metal NPs-mediated reactions are commonly affected by the method of preparation, the source of the metal, the reaction conditions, and the use of additives such as stabilizing agents [3]
Focusing on one of the most studied indium-mediated transformations of organic compounds [18,19], and prompted by our interest in the search of new and useful synthetic applications of metal NPs, we decided to explore the performance of our indium nanoparticles (InNPs)-based reactive system in the allylation of a variety of aldehydes and ketones To the best of our knowledge, this is the first report describing the use of naked InNPs in a synthetic organic transformation
Summary
The synthesis of metal nanoparticles (NPs) has attracted significant attention because of their unique physical and chemical properties. The above mentioned transition-metal NPs were prepared under mild reaction conditions, in tetrahydrofuran (THF) as the solvent and at room temperature, from the corresponding commercially available metal chlorides.
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