Efficient one-pot synthesis of propargylamines catalysed by gold nanocrystals stabilized on montmorillonite

Size selective Au-0-nanoparticles were generated in situ in the nanopores of modified montmorillonite. The modification of montmorillonite was carried out with HCl under controlled conditions for generating nanopores (less than 8 nm) in the matrix and these nanopores acted as hosts for the in situ generation of Au-0-nanoparticles. The synthesis consisted of impregnation of the acid-activated montmorillonite with HAuCl4 aqueous solution followed by reduction with NaBH4. The synthesised Au-0-nanoparticles crystallized in the face centred cubic lattice were single crystals with a preferential growth direction along the (111) plane. A N-2 adsorption-desorption study revealed specific surface areas of 327-579 m(2) g(-1), large specific pore volumes similar to 0.7 cm(3) g(-1), and pore diameters of 0-10 nm of the support. TEM, FESEM and X-ray studies indicate that Au-0-nanoparticles of 0-10 nm were evenly distributed on the support which then serves as an efficient green catalyst for the one-pot, three-component coupling of an aldehyde, an amine and an alkyne via C-H alkyne-activation to synthesize propargylamines with 82-94% yield and 100% selectivity under mild reaction conditions. The nanocatalysts can be recycled and reused several times without significant loss of their catalytic activity.