Polyethylene Glycol (PEG‐400) as Methylene Spacer and Green Solvent for the Synthesis of Heterodiarylmethanes under Metal‐Free Conditions
Rahul Kumar, Deepa Rawat, Subbarayappa Adimurthy
Abstract
Polyethylene glycol 400 (PEG‐400) has been employed as a green, biodegradable solvent as well as methylene spacer for the one‐pot synthesis of heterodiarylmethanes under metal‐free conditions. PEG‐400 is used for the dimerization of both symmetrical and unsymmetrical fused heterocycles and arenes as methylene spacer. The reaction was facilitated by (diacetoxyiodo)benzene (PIDA) as an oxidant. This reaction proceeds without transition metal, base, ligand, and under additive‐free conditions involving the coupling of sp 3 and sp 2 ‐hybridized carbon atoms. The method is applicable for variety of heterocycles such as imidazopyridines, imidazothioazoles, imidazobenzothiozoles, indolizines, indole, 1‐methyl‐1H‐indole, N,N ‐dimethylaniline and trimethoxybenzene. Good to excellent yields and applicability to gram‐scale synthesis demonstrate the potential scope of the process for commercial/industrial applications.