77761-41-2Relevant articles and documents
Tautomerism of 2-hydroxynaphthaldehyde Schiff bases
Antonov, Liudmil,Fabian, Walter M.F.,Nedeltcheva, Daniela,Kamounah, Fadhil S.
, p. 1173 - 1179 (2007/10/03)
A UV-Vis spectroscopic study based on the recently developed chemometric approach for quantitative analysis of undefined mixtures is performed on a series of donor and acceptor substituted Schiff bases of 2-hydroxynaphthaldehydes. In CCl4 solution all compounds preferentially exist as the phenol tautomer independent of the nature of the respective substituent. With increasing polarity the tautomeric equilibrium is shifted towards the quinone form. In CHCl3 and, especially, ethanol a clear distinction between the effect of donors (stabilization of the quinone form) and acceptors (stabilization of the phenol tautomer) is evident. Ab initio calculations including solvent effects via the polarized continuum model of solvation as well as the supermolecule approach are used to rationalize the experimental findings.
A Broadly Applicable Synthesis of Fluorescent Condensed α-Pyrones
Wolfbeis, Otto S.,Ziegler, Erich,Knierzinger, Andreas,Wipfler, Helmut,Trummer, Iris
, p. 93 - 112 (2007/10/02)
In a two step procedure and in usually good yield an α-pyrone ring can be annelated to (enolized) cyclic β-dicarbonyl compounds like 4-hydroxy-2-pyrones, 4-hydroxycoumarins, 4-hydroxy-2-quinolones and more complex malonylheterocycles, but also to β-naphthole. In a first step the combined action of triethyl orthoformate and arylamines upon the dicarbonyl system affords the anilinomethylene derivatives B in usually high yields.B is reacted with an active methylene nitrile (like alkyl cyano-acetates) and one equivalent of a strong base (like sodium methoxide or potassium hydroxide) in a polar aprotic solvent (like dimethylformamide).Subsequent acidification with dilute aqueous acid gives the corresponding α-pyrone D with yields from 18 to 84percent. The reaction sequence is broadly applicable, which is demonstrated by the synthesis of a series of known (3, 7, 16, 31) and novel (10, 19, 22, 25, 28, 34) heterocyclic systems.Most of them exhibit strong fluorescence in the visible with emission maxima between 450 and 510 nm. - Keywords: Enamines; Fluorescence; α-Pyrone, synthesis
