A Novel Mechanistic Study on Ultrasound-Assisted, One-Pot Synthesis of Functionalized Benzimidazo[2,1-b]quinazolin-1(1H)-ones

Abstract

Ultrasound-assisted synthesis of benzimidazo[2,1-b]quinazolin-1(1H)-ones was achieved via piperidine-catalyzed three-component reaction of 2-aminobenzimidazoles, an aromatic aldehyde, and 1,3-dione in aqueous isopropanol. This mechanism was first suspected following our identification of unusual reaction intermediates in a one-pot reaction. An unprecedented coupling reaction, it involved a nucleophilic attack by 2-aminobenzimidazole on in situ generated Michael adduct, followed by electrocyclic ring formation reaction. In contrast to the commonly accepted mechanism, that the direct reaction of 2-amino benzimidazole with a Knoevenagel adduct cannot deliver target compounds.

Synthesis of Tetrahydrotriazoloacridines: A Synergistic Effect of Microwave Irradiation and Brönsted Acidic Ionic Liquids

“…Recently, the mechanistic studies on the multicomponent reactions was reported in literature under basic conditions that involve the nucleophilic attack of an amine on the in situ generated Michael adduct intermediate followed by six‐electron ring cyclization . It is contrary to the common belief of the accepted mechanistic route.…”

ZnO-Nanoparticles-Catalyzed Synthesis of Poly(tetrahydrobenzimidazo[2,1-b]quinazolin-1(2H)-ones) as Novel Multi-armed Molecules

“…[45][46][47][48][49] Among different metal oxides, ZnO nanoparticles have been widely used as an efficient environmentally friendly catalyst due to its high catalytic activities and reactivity in various organic transformations. [50][51][52][53] In connection with these findings, and in continuation of our work on multicomponent reactions [54][55][56][57][58][59][60][61][62][63] as well as on the synthesis of multi-armed molecules, [64][65][66][67][68][69][70] we report herein the synthesis of novel poly(tetrahydrobenzo [4,5]imidazo[2,1-b]quinazolinones) linked to a benzene or methane core via phenoxymethyl or benzoyloxy spacers.…”

“…Fused heterocyclic compounds containing nitrogen are frequently investigated for their wide range of biological activities that are not shown in each homonuclear scaffold. Among them, tetrahydrobenzo [4,5]imidazo [2,1-b]quinazolinones have received considerable attention because of their reported pharmacological applications. [1][2][3][4][5][6] Moreover, multicomponent reactions (MCRs) have recently gained a new dimension in the field of organic synthesis.…”

“…Among them, tetrahydrobenzo [4,5]imidazo [2,1-b]quinazolinones have received considerable attention because of their reported pharmacological applications. [1][2][3][4][5][6] Moreover, multicomponent reactions (MCRs) have recently gained a new dimension in the field of organic synthesis. This strategy has been used to create new collections of diverse bioactive heterocyclic molecules.…”

“…The therapeutic importance of tetrahydrobenzo [4,5]imidazo[2,1-b]quinazolinones 4 [1][2][3][4][5][6] stimulated the development of different strategies for the synthesis of novel derivatives of these compounds. The common protocol for the synthesis of 4 included a three-component reaction of aldehyde 1, dimedone (2), and aminobenzimidazole (3) in the presence of acid, base, or heterogeneous catalysts (Scheme 1).…”