The Use of 4-(3,4-Dichlorophenyl)-4-Oxo-2-(4-Antipyrinyl)-Butanoic Acid in the Preparation of Some New Heterocyclic Compounds With Expected Biological Activity

Reaction of 4-oxo-4-(3,4-dichlorophenyl)-2-butenoic acid (1) with antipyrin (2) gave the corresponding butanoic acid 3. Reaction of 3 with hydrazines gave the pyridazinone derivatives 5a,b. Compounds 5a,b were used to prepare the corresponding dithio derivatives. Reaction of 5a with POCl3 unexpectedly gave the chloropyridazine derivative 7, which is used to prepare the corresponding thio derivative. The hitherto unknown reactions of this chloro derivative with 2-amino-3-carbethoxy-4,5-dimethylthiophene and 2-amino-3-carbethoxy tetrahydrobenzothiophene have now been described. The behaviour of the chloro derivative toward hydrazine hydrate, sodium azide and anthranilic acid was also studied. Some of the new compounds showed antimicrobial and antifungal activities.


Introduction
Antipyrin derivatives are reported to exhibit analgesic and anti-inflammatory effects [1][2][3], antiviral [4], antibacterial [5] and herbicidal [6] activities and have also been used as hair colour additives [7] and to potentiate the local anesthetic effect of lidocaine [8]. This prompted us to synthesize a new series of heterocyclic compounds containing the antipyrinyl moiety. The antimicrobial activities of several of the compounds were screened. The various compounds prepared are outlined in Schemes 1 and 2.

Biological Screening
The antimicrobial activity of the prepared compounds 3, 4, 6, 8, 10, 12a, 13 and 17 was tested by the disk diffusion method [11]. The results of antimicrobial activity are listed in Table 1

General
All melting points are uncorrected, IR spectra (KBr) were recorded on a Unicam SP 1200 spectrophotometer using KBr wafer technique and are expressed as υ (cm-1). Nmr spectra were recorded on a Jeol 100 FT instrument using tetramethylsilane as internal standard and are expressed in δ (ppm) units. Mass spectra were obtained with an GCMS-QP 100 EX mass spectrometer. Analytical data for the prepared compounds is summarized in Table 2.

Preparation of an authentic sample of 7.
Hydrazine hydrate (0.01 mol) was added to a solution of 1 (0.01 mol) in absolute ethanol (50 mL), and the reaction mixture was refluxed for 5 hrs. The solid that separated on cooling was recrystallized from ethanol to give the corresponding pyridazinone. A mixture of the obtained pyridazinone (0.01 mol) and POCl 3 (10 mL) was refluxed for 3 hrs, cooled, treated with crushed ice. The solid obtained was filtered off and crystallized from pet. ether (b.p. 80-100 o C) to give 7, identified by m.p. and mixed m.p. determinations [10].

Biological testing
Whatman No1 filter paper disks were sterilized by autoclaving for one hr. at 140°C. The sterile disks were impregnated with the test compounds. Agar plates were uniformly surface inoculated with fresh broth culture of Staphylococcus aureus and Bacilus cereus (as examples of Gram positive strains), Serratia marcescens and Proteus merabilis (as Gram negative strains) and Aspergillus fungytus (as fungus). The impregnated disks were placed on the medium suitably spaced apart and the plates were incubated at 5°C for 1 hr to permit good diffusion and then transferred to an incubator at 28°C for 24 hr. The inhibition zones were then measured.