The integrated one-pot synthesis of valuable allylamines
and alkylamines
from amines, formaldehyde, and terminal alkynes is achieved using
a single catalyst material. This multifunctional catalytic system
is composed of a silica support on which are jointly assembled ruthenium
nanoparticles and covalently functionalized copper N-heterocyclic carbene (NHC) complexes, introducing a new generation
of nanoparticles immobilized on molecularly modified surfaces. The
textural, structural, morphological, and electronic properties of
the resulting Ru@SiO2-[Cu-NHC] material were studied by
a variety of techniques including N2 adsorption, solid-state
NMR, electron microscopy, and X-ray photoelectron spectroscopy. Ru@SiO2-[Cu-NHC] was found active and selective for the one-pot synthesis
of a wide range of allylamines and alkylamines, products of great
importance in the fine chemical and pharmaceutical industry. Detailed
investigations evidenced that the immobilized molecular Cu(I)–NHC
complex is responsible for the atom-efficient A3 coupling
of amines, formaldehyde, and terminal alkynes, while the selective
hydrogenation of the resulting propargyl amines is catalyzed by Ru(0)
nanoparticles. The design strategy and the preparation method to combine
molecular and nanoparticle sites on a single support are flexible,
opening the way to the development of multifunctional catalytic systems
capable of performing complex reaction sequences in one pot.
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