A facile protocol for the synthesis of 3-aminoimidazo-fused heterocycles via the Groebke–Blackburn–Bienayme reaction under catalyst-free and solvent-free conditions

Zirconium Metal‐Organic Framework (UiO‐66) as a Robust Catalyst toward Solvent‐Free Synthesis of Remarkable Heterocyclic Rings

“…From both economic and environmental viewpoints, organic synthesis under solvent‐free conditions has gained prominence in the recent decade due to decreasing the pollutant production, reduced utilization or elimination of toxic and expensive organic solvent along with operational simplicity . Solvent‐free MCRs are in compliance with the philosophy of green chemistry since that can improve E‐factor and mass intensity . MCRs are versatile approaches to the simple and rapid generation of small‐molecule libraries with high skeletal diversity and complexity accompanied by significant atom and bond economy .…”

Solvent–free Multicomponent Synthesis of Biologically–active Fused–imidazo Heterocycles Catalyzed by Reusable Yb(OTf)3 Under Microwave Irradiation

“…To gauge the greenness of the present protocol, we evaluated the green chemistry metrics (such as E‐factor and Mass Intensity) in conjunction with the reported protocols based on either conventional or microwave heating (Table ). The results clearly indicate that our protocol is far better than the literature reports by exhibiting excellent E‐factor which is almost zero and Mass Intensity which is nearly one (entry 10). In comparison with all the methods listed in Table (entries 1–9; were required either column chromatography or recrystallization at the end), the present method (entry 10) doesn't need any type of purification and the solvents (used for workup) and catalyst were recycled incessantly ( vide supra ).…”

“…In addition, many of those reported methods required longer reaction time (Table , entries 2, 3, 6, 7 and 9), which may lead to the decomposition of the product/reactant and or formation of the side products. For instance, the reaction involving enolizable aldehyde 2 f produced the desired product 4 o with 63 % isolated yield under conventional heating condition (by following the solvent‐free and catalyst‐free protocol; Table , Method A). However, the reaction also produces enamine 7 as the side product .…”

A decade update on solvent and catalyst-free neat organic reactions: a step forward towards sustainability

“…98 Sharada et al, in 2014, synthesized 3aminoimidazo-fused heterocycles through greener approach by Groebke-Blackburn-Bienayme reaction using 2-amino heterocycles, isocyanides, and aldehydes under solvent and catalyst-free conditions. 99 Initially, they performed a three components reaction taking 2-aminopyridine (172), cyclohexylisocyanide (181) and benzaldehyde (182) at various temperatures and found at 160 °C the desired product (183) was formed within 2 h in excellent yield (95%) (Scheme 51). After optimization various substituted 2-aminopyridines, aromatic aldehydes and isonitriles were subjected to prove the general applicability of this procedure.…”