No abstract

Different methodologies for transition metal-free Ullmann condensation reactions.

A novel and easy-to-synthesize chemosensor (L) was developed for the selective sensing of Cu2+ ions in mixed aqueous medium.

A simple metal free alternative procedure for Ullmann type C−N coupling reactions has been achieved by allowing substituted bromo/chloro anthraquinones to react with a variety of amines in the presence of Choline hydroxide (ChOH). This reaction is also extended towards synthesis of commercially available Acid Blue 25 dye. Good to excellent yields (78‐95%) of N‐aryl anthraquinone products were obtained under mild conditions in reduced reaction time. This reaction is driven by SNAr mechanistic pathway, moreover compared to conventional methods, no metal catalyst is required, ChOH is an environmentally benign, cheaper catalyst recyclable up to five runs without remarkable loss of activity.

An efficient and facile route has been developed by using greener and reusable deep eutectic solvent (DES) for the synthesis of O-arylated ethers. This process involves nucleophilic aromatic substitution (S N Ar) of various strongly electrondeficient aryl/alkyl halides and phenols with different substituents resulting in good to excellent yields of products (80-96 %). A significant enhancement in the yield as well as rate of the reaction is observed with increase in presence of electron-withdrawing functionality attached to aryl halide moiety. Simplicity of this catalytic system, cheap cost and easy product isolation procedure makes this protocol economically viable and comparable to metal/ligand catalysed reactions utilizing aprotic solvents. Moreover, the other significant advantages of this method includes mild reaction conditions, short reaction times, easy work up procedure and recyclability of the catalyst up to four runs without remarkable loss in activity.