2-Hydroxynaphthalene-1,4-dione

The same group also established a rapid and regioselective synthesis of benzo[h]pyrazolo[3,4-l)]quinolines 85 (Scheme 12.32) [53]. The reaction could be conducted by using aldehydes 69, 5-aminopyrazoles 80, and 2-hydroxynaphthalene-1,4-dione 33b as substrates under microwave irradiation within short a time of 10-26 min. Good to excellent chemical yields (61-91%) and complete regioselec-tivity were achieved for 22 examples. 

Xu et al. examined the reaction of 2-hydroxynaphthalene-1,4-dione with various aldehydes, including formaldehyde 72,... 

Keywords Isocyanides, dialkyl acetylenedicarboxylates, 2,5-dihydroxycyclohexa-2,5-diene-1,4-dione, 2-hydroxynaphthalene-l,4-di(Mie, acetonitrile, room temperature, one-pot multi-component synthesis, functionalized hfs(47/-chromeme) and 4//-benzo[g]chromene derivatives... 

Bicyclic—monocyclic valence isomerization of a radical dianion in the bicyclo[3 1.0]hexanesemidione system has been demonstrated. Symmetrical 1,4-semldiones formally derived from cycloheptatriene and cyclobctatetraene perfer to exist in the bicyclic (4.1.0 and 4.2.0) structures. Bicyclic—monocyclic valence isomerization in the bicyclo[4.1.0]hept-3-ene-2,5-dione system occurs more readily for the dianion than for the radical anion. Several radical anions derived from the (CH)6 io annulenes are reported. In the case of the 1,2-oxygenated derivatives of (CH)io the dianions or radical anions are stable, but the diones undergo valence isomerization and under oxida-time conditions are converted to 4-hydroxynaphthalene-1,2-semiquinone. Enediol dianions in the bicyclo [2.2 l]hepta-2,5-dione and l-carbQalkoxybicyclo[3 2.1] octa-2,6-diene systems have been observed to undergo... 

An efficient and practical route to a novel fluorescent benzo[a]pyrano[2,3-c] phenazine framework has been developed by a one-pot, four-component reaction of 2-hydroxynaphthalene-l,4-dione, 1,2-DABs, aromatic aldehydes, and Meldram s acid in glacial acetic acid at 70 °C (Saluja et al. 2014). 

In their report, Khurana and his group [81] also showed that DBU (10mol%) can effectively catalyze the three-component cyclocondensation reaction between aromatic aldehydes, malononitrile or ethyl 2-cyanoacetate, and 2-hydroxynaphthalene-l,4-dione in aqueous medium under reflux to afford 2-amino-4H-benzo[ ] chromenes (10). A series of diversely substituted 2-amino-4-aryl-5,10-dioxo-5,10-dihydro-4ff-benzo[g]chromene-3-carbonitriles and ethyl-2-amino-4-aryl-5,10-dioxo-5,10-dihydro-4H-benzo[j]chromene-3-carboxylates were synthesized using this protocol in excellent yields (Scheme 5). The reactions were claimed to be remarkably clean, and no chromatographic purification was required. 

On replacing 2-hydroxynaphthalene-l,4-dione (21) by 4-hydroxy-6-methyl-2H-pyran-2-one (11), Bazgir and his group obtained another series of spiro[indole-3,4 -pyrano[4,3-li]pyran]-3 -carbonitriles (23) under the same reaction conditions they even synthesized these scaffolds using magnetically recoverable and reusable CuFe204 nanoparticles as well in aqueous media (Scheme 12) [112,113], Besides, sodium stearate was also efficiently used in S5mthesiz-ing this spirooxindole scaffold in aqueous micellar media [114],... 

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