(7-Hydroxy-2-oxo-2H-chromen-4-yl)-acetic acid hydrazide (2) was prepared from (7-hydroxy-2-oxo-2H-chromen-4-yl)-acetic acid ethyl ester (1) and 100% hydrazine hydrate. Compound 2, is the key intermediate for the synthesis of several series of new compounds such as Schiff's bases 3a-l, formic acid N'-[2-(7-hydroxy-2-oxo-2H-chromen-4-yl)acetyl] hydrazide (4), acetic acid N'-[2-(7-hydroxy-2-oxo-2H-chromen-4-yl)-acetyl] hydrazide (5), (7-hydroxy-2-oxo-2H-chromen-4-yl)-acetic acid N'-[2-(4-hydroxy-2-oxo-2H-chromen-3-yl)-2-oxoethyl] hydrazide (6), 4-phenyl-1-(7-hydroxy-2-oxo-2H-chromen-4-acetyl) thiosemicarbazide (7), ethyl 3-{2-[2-(7-hydroxy-2-oxo-2H-chromen-4-yl)-acetyl]hydrazono}butanoate (8), (7-hydroxy-2-oxo-2H-chromen-4-yl)-acetic acid N'-[(4-trifluoromethylphenylimino)methyl] hydrazide (9) and (7-hydroxy-2-oxo-2H-chromen-4-yl)acetic acid N'-[(2,3,4-trifluorophenylimino)-methyl] hydrazide (10). Cyclo-condensation of compound 2 with pentane-2,4-dione gave 4-[2-(3,5-dimethyl-1H-pyrazol-1-yl)-2-oxoethyl]-7-hydroxy-2H-chromen-2-one (11), while with carbon disulfide it afforded 7-hydroxy-4-[(5-mercapto-1,3,4-oxadiazol-2-yl)methyl]-2H-chromen-2-one (12) and with potassium isothiocyanate it gave 7-hydroxy-4-[(5-mercapto-4H-1,2,4-triazol-3-yl)methyl]-2H-chromen-2-one (14). Compound 7 was cyclized to afford 2-(7-hydroxy-2-oxo-2H-chromen-4-yl)-N´-(4-oxo-2-phenyliminothiazolidin-3-yl) acetamide (15). Molecules 2006, 11 135

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Reactions of 4-chloro-3-nitrocoumarin with a variety of nucleophiles produced a number of novel substituted coumarins. Hard and borderline nucleophiles exclusively substitute chlorine in position 4, while soft nucleophiles substitute the nitro group in position 3 (except for iodide) of the title compound. This result of the nucleophilic substitution of 4-chloro-3-nitrocoumarin is rationalized in terms of the HSAB model. Chemie der Cumarine. -Nucleophile Substitutionen an 4-Chlor-3-nitrocumarin mit harten und weichen NucleophilenUmsetzungen von 4-Chlor-3-nitrocumarin mit verschiedenen Nucleophilen ergaben zahlreiche ncue substituierte Cumarine. Harte Nucleophile und solche im Ubergangsbereich zu den weichen substituieren ausschliefllich das Chlor in Position 4, wahrend weiche Nucleophile (mit Ausnahme von Iodid) die Nitrogruppe in Position 3 der Titelverbindung ersetzen. Dieses Ergebnis wird mit Hilfe der Theorie von den harten und weichen Sauren/Basen diskutiert.Compounds containing a coumarin subunit possess a wide range of biological activities and show an interesting chemical reactivity' -9 ) . This is the consequence of the rich electronic structure of coumarin which offers abundant possibilities for diversified activity and reactivity of the system. In the course of our studies"."' on the chemistry of coumarins and related structures we have investigated reactions for the preparation of a number of differently 3,4-substituted coumarins. We found that Pearson's HSAB (hard and soft acids and bases) concepti2-") of preferred interactions of hard acids (acceptors) with hard bases (donors) and soft acids (acceptors) with soft bases (donors) may be used in the case of nucleophilic attack on 4-chloro-3-nitrocoumarin (1) as a guiding principle for predicting the effect of substitution. The nucleophilic substitutions of 4-chloro-3-nitrocoumarin with a variety of nucleophiles, classified as hard, soft, and borderline"), led t o a number of novel substituted coumarins.

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