Lignin@Ni‐NPs: A Novel, Highly Efficient, Recyclable, and Selective Nanocatalyst for Base‐Free Transfer Hydrogenation Reactions at Room Temperature

Abstract

Nickel nanoparticles were synthesized readily by sonication of a mixture of nickel(II) chloride hexahydrate, hydrazine hydrate, lignin and water at 60 °C. This lignin supported nickel nanoparticles (Lignin@Ni‐NPs) have been characterized by UV‐Visible, PXRD, EDX, SEM and TEM techniques. The average size of Ni‐NPs was found in the range of 15‐20 nm as revealed by TEM micrographs. The amount of nickel(0) loaded in Lignin@Ni‐NPs determined by EDX was 36.6 %. The catalytic activity of Lignin@Ni‐NPs have been evaluated in the transfer hydrogenation of carbonyl compounds into the corresponding alcohols. The catalyst have been found efficient for hydrogen‐transfer reduction of functionalised and non‐fuctionalised including heteroaromatic carbonyl compounds as the desired alcohols were obtained in high yields of about 90‐95 % at room temperature, under base‐free conditions and in short reaction times. The catalyst was recovered by simple filtration and it has an advantage of being reuable more than six times without significant loss in its catalytic activity.

Cobalt‐Promoted Transfer Hydrogenation of Azaaryl Ketones by Using Formate as the Hydrogen Source

“…One of which employs an iron(II) catalyst with large excess of potassium formate as hydride source [5a] . The other applies a nickel(0) nanocatalyst using ammonium formate as reductant [5b] . Therefore, an efficient and operationally simple method for selective reduction of 2‐pyridyl ketones is highly desirable.…”