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Synthesis and spectral properties of 7‐( N ‐arylsulfonyl)aminocoumarins, a new class of fluorescent p H indicators
Author(s) -
Wolfbeis Otto S.,
Baustert John H.
Publication year - 1985
Publication title -
journal of heterocyclic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.321
H-Index - 59
eISSN - 1943-5193
pISSN - 0022-152X
DOI - 10.1002/jhet.5570220514
Subject(s) - chemistry , fluorescence , cyanation , bromine , aqueous solution , cyanide , medicinal chemistry , orange (colour) , photochemistry , organic chemistry , inorganic chemistry , nuclear chemistry , catalysis , food science , physics , quantum mechanics
7‐Arylsulfonylamino‐coumarins 3 and 5 , with electron‐delocalizing substituents in position 3 were obtained by condensation of 4‐arylsulfonylamino‐2‐hydroxybenzaldehyde with various (hetero)arylacetic esters and by other methods. Oxidative cyanation using potassium cyanide and elemental bromine gave the corresponding 4‐cyano derivatives 6a,b. The absorption and emission maxima of coumarins 3 and 5 in organic solvents and in water of different pH were determined. All showed bright blue fluorescence in organic or acidic aqueous solution, which is shifted to the green in alkaline solution. The 4‐cyano derivatives 6a, b exhibit green fluorescences, which change to yellow in alkaline solution. Simultaneously the color changes from yellow to orange. The p K a values of compounds 3 and 5 were found to lie between 6.33 and 7.06, whereas for the 4‐cyano derivatives they were distinctly lower (5.66‐5.95). The spectral changes observed in the near neutral p H range may render the new compounds useful indicators for the measurement of physiological p H's.