One-pot synthesis of chromeno[2,3-b]isoindolo[1,2-e]pyrrole-12,13-dione derivatives by sequential reaction of ninhydrin, 2-aminochromen-4-ones and arylamines

One-pot domino synthesis of five- and six-membered fused dihydropyridines promoted by PPh3-NBS in aqueous medium

A facile one-pot synthesis of five- and six-membered fused dihydropyridines such as chromenodihydropyridines, pyrazolodihydropyridines and isoxazolopyridines was accomplished for the first time by employing PPh₃-NBS via a formal [3 + 2 + 1] cycloaddition of 1,3-bisnucleophiles (i.e., 2-aminochromone, 4-aminochromone, 5-aminopyrazole and 5-aminoisoxazole), β-enaminones and aldehydes in aqueous medium. The present approach involves a Michael type addition followed by intramolecular cyclization leading to the formation of two new C-C bonds and one C-N bond. High compatibility and excellent yields are the advantages of this protocol.

DBU-Mediated Domino Annulation Reaction of 2-Amino-4H-chromen-4-ones and Aromatic Aldehydes for Synthesis of Polysubstituted 3-Hydroxy-5H-chromeno[2,3-b]pyridinones

A pseudo-three-component annulation reaction of substituted 2-amino-4H-chromen-4-ones with aromatic aldehydes promoted by DBU was investigated to access polysubstituted 5H-chromeno[2,3-b]pyridines. This reaction included a sequential intermolecular nucleophilic addition/Michael cyclization/intramolecular epoxidation/ring opening/aromatization sequence, which possessed excellent step and atom economy in a single operation for generating 3-hydroxy-5H-chromeno[2,3-b]pyridines from readily available substrates.

Recent applications of ninhydrin in multicomponent reactions

Ninhydrin (1,2,3-indanetrione hydrate) has a remarkable breadth in different fields, including organic chemistry, biochemistry, analytical chemistry and the forensic sciences. For the past several years, it has been considered an important building block in organic synthesis. Therefore, there is increasing interest in ninhydrin-based multicomponent reactions to rapidly build versatile scaffolds. Most of the works described here are simple reactions with readily available starting materials that result in complex molecular architectures. Some of the synthesized compounds exhibit interesting biological activities and constitute a new hope for anticancer agents. The present review aims to highlight the multicomponent reactions of ninhydrin towards diverse organic molecules during the period from 2014 to 2019.

This article aims to review recent multicomponent reactions of ninhydrin towards diverse organic scaffolds, such as indeno-fused heterocycles, spiro-indeno heterocycles, quinoxalines, propellanes, cage-like compounds, and dispiro heterocycles.

Cascade process for direct synthesis of indeno[1,2-b]furans and indeno[1,2-b]pyrroles from diketene and ninhydrin

Novel and efficient multicomponent reactions (MCRs) involving diketene, ninhydrin (indane-1,2,3-trione) and one primary amine (3CR) or two different primary amines (4CR) were achieved for the successful synthesis of dihydro-4H-indeno[1,2-b]furan-3-carboxamides or tetrahydroindeno[1,2-b]pyrrole-3-carboxamides, respectively. The merits of this method are highlighted by using either commercially available or easily accessible starting materials, operational simplicity, facile workup procedure, efficient usage of all the reactants, tolerance of a variety of functional groups and ability to conduct under un-catalyzed reaction condition. The products were also isolated by just decantation of the solvent, and for the purification column chromatography was non-required.

Design and synthesis of dichromeno[2,3-b;3′,2′-e]pyridine-12,14-dione to evaluate its optical properties

An unambiguous synthesis of dichromeno[2,3-b;3′,2′-e]pyridine-12,14-diones has been developed under mild conditions and their optical properties have been evaluated by studying UV-vis absorption and photoluminescence (PL) spectroscopy, cyclic voltammetry (CV) measurements, DFT calculations and thermogravimetric analysis.