Indium-based metal–organic frameworks as catalysts: synthesis of 2-nitro-3-arylimidazo[1,2-a]pyridines via oxidative amination under air using MIL-68(In) as an effective heterogeneous catalyst

Abstract

Indium-based metal-organic frameworks as catalysts: synthesis of 2-nitro-3-arylimidazo[1,2-a] pyridines via oxidative amination under air using MIL-68(In) as an effective heterogeneous catalyst † The metal-organic framework MIL-68(In) has emerged as a productive heterogeneous catalyst for the synthesis of 2-nitro-3-arylimidazo[1,2-a]pyridines via oxidative amination between 2-aminopyridines and nitroalkenes using air as an oxidation agent. The catalyst displayed impressively higher efficiency for the generation of 2-nitro-3-arylimidazo[1,2-a]pyridines than various other MOFs and several common homogeneous catalysts. Heterogeneous catalysis was verified for the reaction of 2-aminopyridines with nitroalkenes employing the framework-based catalyst. It was possible to collect and reuse the catalyst for the production of 2-nitro-3-arylimidazo[1,2-a]pyridines without a pronounced deterioration in catalytic efficiency. To the best of our knowledge, the preparation of 2-nitro-3-arylimidazo[1,2-a] pyridines has not been formerly conducted utilizing heterogeneous catalysts. Furthermore, indium-based catalysts were not previously employed for this transformation. Scheme 1 Synthesis of 2-nitro-3-phenylimidazo[1,2-a]pyridine utilizing MIL-68(In) catalyst. Fig. 1 Yields of 2-nitro-3-phenylimidazo[1,2-a]pyridine at varied temperatures.

Engineering Metal–Organic Framework Catalysts for C−C and C−X Coupling Reactions: Advances in Reticular Approaches from 2014–2018

“…MIL‐68(In) was used by Ha and co‐workers for oxidative amination reactions. The MOF was synthesized by the high‐temperature polymerization of indium nitrate with terephthalic acid and characterized by using PXRD, TGA, FTIR, SEM, TEM, and AAS.…”

Recent Advances in the Synthesis of Imidazo[1,2‐a]pyridines: A Brief Review

“…Ha et al . reported the synthesis of 2‐nitro‐3‐arylimidazo[1,2‐ a ]pyridines 167 via oxidative amination between 2‐aminopyridine derivatives 165 and nitroalkenes 166 utilizing the framework MIL‐68(In) as an effective heterogeneous catalyst using air as an oxidation agent in good yields [132] . Initially, 2‐aminopyridine forms a Michael adduct A through Michael addition in an endocyclic manner.…”

NIS‐promoted multicomponent reaction of 2‐aminopyridines with aldehydes and nitromethane for the synthesis of 3‐nitroimidazo[1.2‐a]pyridines

“…This structure has also been found in several commercial drugs, including zolpidem, saripidem, zolimidine, and olprinone . Hence, the syntheses of these compounds have drawn significant attention in the past decade …”