A one-pot three-component reactions for the synthesis of fully substituted spiro indeno[1,2-b]quinoxaline derivatives

A General Method for the Synthesis of 11H-Indeno[1,2-B]Quinoxalin- 11-Ones and 6H-Indeno[1,2-B]Pyrido[3,2-E]Pyrazin-6-One Derivatives Using Mandelic Acid as an Efficient Organo-Catalyst at Room Temperature

Aims:

Synthesis of 11H-indeno[1,2-b]quinoxalin-11-ones as well as 6H-indeno[1,2-b]pyrido[3,2-e]pyrazin-6-one derivatives under greener conditions.

Background:

Quinoxaline and related skeletons are very common in naturally occurring bioactive compounds.

Objective:

Design a facile, green and organo-catalyzed method for the synthesis of 11H-indeno[1,2-b]quinoxalin-11-ones as well as 6H-indeno[1,2-b]pyrido[3,2-e]pyrazin-6-one derivatives.

Methods:

Both the scaffolds were synthesized via the condensation of ninhydrin and o-phenylenediamines or pyridine-2,3-diamines respectively by using a catalytic amount of mandelic acid as an efficient, commercially available, low cost, organo-catalyst in aqueous ethanol at room temperature.

Results:

Mild reaction conditions, use of metal-free organocatalyst, non-toxic solvent, ambient temperature, and no column chromatographic separation are some of the notable advantages of our developed protocol.

Conclusion:

In conclusion, we have developed a simple, mild, facile and efficient method for the synthesis of structurally diverse 11H-indeno[1,2-b]quinoxalin-11-one derivatives via the condensation reactions of ninhydrin and various substituted benzene-1,2-diamines using a catalytic amount of mandelic acid as a commercially available metal-free organo-catalyst in aqueous ethanol at room temperature. Under the same optimized reaction conditions, synthesis of 6H-indeno[1,2-b]pyrido[3,2-e]pyrazin-6-one derivatives was also accomplished with excellent yields by using pyridine-2,3-diamines instead of o-phenylenediamine.

Recent advancement in the synthesis of diverse spiro-indeno[1,2-b]quinoxalines: a review

The nitrogen-containing indeno[1,2-b]quinoxaline ring is a privileged structurally fused active system and has notable applications in various fields of chemistry.

The application of blocked isocyanate chemistry in the development of tunable thermoresponsive crosslinkers

The synthesis of a novel monomer, methacryloyl pyrazole, and its subsequent reaction with diisocyanates to produce thermoresponsive crosslinkers is reported.

Synthesis of 4,5-dihydropyrazolyl-2H-indenediones by Aldol Condensation of Ninhydrin with 1H-pyrazol-5-ol

A simple and efficient procedure for the synthesis of 2-hydroxy-2-(5-hydroxy-1H-pyrazol-4-yl)-2H-indene-1,3-dione derivatives, proceeding via aldol condensation between ninhydrin and various 3-alkyl-1H-pyrazol-5-ols is described. The syntheses were carried out in ethanol at room temperature and proceeded with short reaction times to give the products with high yields.

Heterocyclic ring extension of estrone: synthesis and cytotoxicity of fused pyran, pyrimidine and thiazole derivatives

The one pot reaction of estrone with the aromatic aldehydes 2a-c and either of malononitrile or ethyl cyanoacetate afforded the fused pyran derivatives 4a-f. On the other hand, carrying the same reaction using thiourea instead of the cyanomethylene reagent gave the fused pyrimidine derivatives 6a-c. The latter compounds reacted with phenacyl bromide to give the thiazolo[3,2-a]pyrimidine derivatives 8a-c. The reaction of the title compound with bromine gave the monobromo derivative 13 which in turn reacted with either thiourea or cyanothioacetamide to give the thiazole derivatives 14 and 16, respectively. The cytotoxicity of the newly synthesized products was evaluated against six human cancer and normal cell lines where the results showed that compounds 4c, 4f, 6b, 8b, 8c, 10, 13, 16, 18c and 19c exhibited optimal cytotoxic effect against the cancer cell lines, with IC50's in the nM range.