Covalently immobilized indium(III) composite (In/SiO2) as highly efficient reusable catalyst for A3-coupling of aldehydes, alkynes and amines under solvent-free conditions

• Synthesis and complete characterization of a supported indium composite (In/SiO2).
• Identification that the indium is bonded to silica through covalent InOSi bonds.
• Synthesis of propargylamines through an A3-coupling reaction promoted by In/SiO2.
• Microwave assisted reactions.
• The supported In composite could be reused for four times without losing efficiency.

We describe the synthesis and application of a silica-xerogel-supported indium(III) composite (In/SiO2). Using X-ray photoelectron spectroscopy, by the first time it was possible to identify that the indium is bonded to the silica through covalent InOSi bonds. The N2 adsorption/desorption isotherms revealed that the In/SiO2 composite presents pores with diameters between 1 and 4 nm, which allows it to be used as a heterogeneous catalyst. Thus, this composite was used as catalyst in an A3-coupling reaction with several aldehydes, amines and acetylenes, leading to the formation of propargylamines in good-to-excellent yields in solvent-free conditions, using both conventional heating and microwave irradiation (MW). The recyclability was evaluated under both conditions and no considerable reduction in the yields was observed after four cycles.

Figure optionsDownload high-quality image (134 K)Download as PowerPoint slideIndium-Silicon linked: A recyclable well characterized hybrid catalyst has been applied in A3-coupling solvent free reaction under conventional and microwave heating to afford propargylamines in high yields.