Advantage of Using NaH₂PO₂ over Alkali Metal Formates as a Hydrogen Source for Pd‐gC₃N₄ Catalyzed Hydro‐Dehalogenation of Aryl Halides

Abstract

Halogenated and polyhalogenated aromatic compounds are known for their toxicity and effect on human health and the environment. These aromatic hydrocarbons have been widely used in pesticides, flame retardants, pharmaceuticals, and other industrial chemicals. The substitution of halogen atoms of aromatic halides by hydrogen atoms in the presence of a metal catalyst is an important organic transformation and is known as a catalytic hydro-dehalogenation reaction. It is an important technique used for the treatment of halogenated industrial waste. Herein, we investigated the comparative hydro-dehalogenation of aryl halides in the presence of Pd-gC 3 N 4 catalyst using various hydrogen transfer sources in an eco-friendly manner. We also investigated the advantage of using sodium hypophosphite (NaH 2 PO 2 ) as a hydrogen source for hydrodehalogenation in comparison to alkali metal formates. For hydro-dehalogenation of 1 mmol of aryl halide, 2 equivalents of NaH 2 PO 2 are used while 4 equivalents of KHCO 2 are required in the presence of 3.8 wt % of Pd metal catalyst. The Pd-GCN catalyst was characterized by various microscopic and spectral techniques such as PXRD, FTIR, SEM, TEM, XPS, and TGA, etc. A gram scale reaction was performed to analyze the industrial potential of the proposed catalytic system. Finally, the recyclability of Pd-GCN was found excellent and the catalyst could run multiple cycles with sustained activity.

Sodium hypophosphite mediated reductive amination of carbonyl compounds with N,N-dialkylformamides

“…Sodium hypophosphite is a cheap, non-toxic, 25 readily available reducing agent capable of carrying out different reductive transformations leaving no hazardous waste. [26][27][28][29][30][31] Hypophosphites of other metals and hypophosphorous acid itself have also been used as reducing agents. 32,33 Recently, a convenient protocol for the reductive amination of carbonyl compounds with amines using sodium hypophosphite as a reducing agent has been published.…”

Ru-gC3N4 Catalyzed Hydrodebenzylation of Benzyl Protected Alcohol and Acid Groups Using Sodium Hypophosphite as a Hydrogen Source

“…Most of these hydrogen sources have been used with the Pd metal catalyst. Alkali hypophosphite salts behave as an effective hydrogen donor in presence of a metal catalyst [32,33]. It decomposes to molecular hydrogen and sodium hydrogen phosphite in presence of catalyst and water.…”