Effective and selective direct aminoformylation of nitroarenes utilizing palladium nanoparticles assisted by fibrous-structured silica nanospheres

Abstract

Palladium nanoparticles (~ 1–3 nm, 0.4 wt% Pd) were uniformly distributed over the surface of fibrous silica nanospheres (KCC-1) modified via aminopropyltriethoxysilane using a fast and cost-effective palladium (II) chloride reduction process. The Pd nanoparticles (Pd NPs) distribution over the ensuing catalyst Pd/KCC-1-NH2 showed much more uniform distribution, and smaller size compared with the tedious hydrothermal reduction method. The morphological, chemical, and size analyses of Pd/KCC-1-NH2 by BET, UV–Vis spectra, XRD, HR-TEM, EDS and XPS analysis revealed that the succeeding material consist of a distinct fibrous silica nanospheres support adorn with Pd NPs. The resultant nanocatalyst was tested for the one-step reductive aminoformylation of aromatic nitro compounds using formic acid. A wide range of substituted nitroarenes including electron withdrawing, releasing, sterically hindered and multifunctional groups have been converted to corresponding aryl formamide in quantitative yields (yields up to 98%) at moderate temperature (70 °C). Optimization study has proved that the 6 equivalent of formic acid is required and toluene was found to be the better solvent. The established practice is beneficial due to the use of formic acid as H2 source and formylating agent, easiness in handling of the catalyst and simple workup procedure with efficient catalyst reusability.