Synthesis and reactions of 4-(arylhydrazino)coumarins

Abstract

Keywords: 4-(arylhydrazino)coumarins, 1-aryl-3-(2-hydroxyphenyl)-2H-pyrazin-5-ones, aromatic aldehydes, 2,3-diaryl[1]benzopyrano [4,3-b]pyrazol-4-ones.In a development of work on the synthesis of coumarins with heterocycles at the C(3)-C(4) bond [1-3] we have synthesized pyrazolocoumarins by the reactions of 4-(arylhydrazino)coumarins with aromatic aldehydes. We reverted to pyrazolocoumarins [4-6] which, like other 3,4-heteroannelated coumarins, were observed to have biological activity [7][8][9][10][11][12][13].The reactions of phenyl-, 2-chlorophenyl-and 4-bromophenylhydrazine hydrochlorides with 4-hydroxycoumarin 1 in the presence of triethylamine were carried out by heating in the absent of solvent (1h 30 min, 90-100ºC). In all cases, 1-aryl-3-(2-hydroxyphenyl)pyrazol-5-ones 3a-c were formed along with the corresponding 4-(arylhydrazino)coumarins 2a-c. Pyrazolone 3a was obtained previously [14] by boiling 4-hydroxycoumarin with phenylhydrazine in benzene. On boiling the same reagents in toluene with a catalytic amount of p-toluenesulfonic acid we obtained 4-(phenylhydrazino)coumarin (2a) as the main product (50%) and the pyrazolone 3a in a yield of only 18%. Boiling the pyrazolones 3a-c in acetic anhydride in the presence of p-toluenesulfonic acid gave the diacetyl derivatives 4a-c.The reaction of (4-arylhydrazino)coumarins 2a-c with 4-chlorobenzaldehyde in DMF solution in the presence of equimolar catalytic amounts of piperidine and acetic acid gave the corresponding 2-aryl-3-(4-chlorophenyl)[1]benzopyrano[4,3-b]pyrazol-4-ones 5a-c.

Synthesis, Tautomeric Structure, Dyeing Characteristics, and Antimicrobial Activity of Novel 4-(2-Arylazophenyl)-3-(2-hydroxyphenyl)-1-phenyl-2-pyrazolin-5-ones

“…Thus, coupling of 1-phenyl-3-(2-hydroxyphenyl)-2-pyrazolin-5-one 3 (lit. 18% yield) 16 with the respective diazotized anilines gave the products 4a, 4b, and 4d that proved identical in all respects (mp., mixed mp., IR and UV.) with those obtained above from the method A (Scheme 1).…”

“…36,[47][48][49] This down field position of N-H proton is in evidence of chelation with the carbonyl group. Other down-field singlet at around 10.5 ppm was assigned to the phenolic OH group [16][17][18] and peaks for aryl protons at 7.01-8.50 ppm. These results were compatible with a conclusion of such compounds 4a-f have the structure (D).…”

“…Hence, progress in the chemistry of it has been inhibited in part because well defined derivative are lacking or difficult to prepare, 15 poor yield, 16,17 and complicated by numerous competing reactions. [15][16][17][18][19] There is a growing demand for development of an alternative technologies.…”

“…Hence, progress in the chemistry of it has been inhibited in part because well defined derivative are lacking or difficult to prepare, 15 poor yield, 16,17 and complicated by numerous competing reactions. [15][16][17][18][19] There is a growing demand for development of an alternative technologies. In view of these facts and in continuations of our studies designed to prepare heterocyclic azodyes with better fastness properties, [20][21][22][23] it was considered worthwhile to synethesize the title compounds, determine their tautomeric structures, and exploring their application in dyeing polyester fabrics and their antimicrobial activity were studied.…”

“…4-hydroxycoumarin (1), 24 2,3,4-chromantrione-3-arylhydrazones 2a-f, 25,26 and 1-phenyl-3-(2-hydroxyphenyl)-2-pyrazolin-5-one (3) 16 were prepared according to literature procedure.…”