Synthesis and study the biological activity of some six, five and fused ring heteroatome systems derived from 2-mercapto benzothiazole

In this paper ,new series of 2-hydrazino benzothiazole [1], 2-N-benzothiazole-N`-phenyl hydrazine carboxamide [2], 2-N-[(3)-N`-phenyl-5-(p-bromophenyl)-2`-hydroxy-1,3-oxazolin-2`-yl] benzothiazol hydrazine [3] , 2-N-benzothiazole-N`-1-naphthyl hydrazine carboxamide [4], 2-N-[(3`)-N`-(1-naphthyl)-5`-(p-bromo phenyl)-2`-hydroxy-1,3-oxazolin-2`-yl)] benzothiazol hydrazine [5], of 2-thiaacetic acid benzothiazole [6] ,2-thiaacetyl chloride benzothiazole [7], 5-amino-2-mercapto-1,3,4-thiadiazole [8], of 2-mercapto-[5-acetamid thiamethyl benzothiazol]-1,3,4-thiadiazole [9], 2-phenyl-5-chloromethyl-1


Introduction
Heterocyclic compounds are considered one of important types of organic compounds due to their applications in drug and industrial studies.Heterocyclic compounds are cyclic compounds in which one or more of the atoms of the ring are hetero atoms.The name comes from the Greek word heteros, which means "different".A variety of atoms such as (N, O, S, Se, P, Si, B and As) can be incorporated into the ring structure (1) .Oxazoline is one of a class of organic heterocyclic compounds containing a five member one unsaturated ring structure composed of one oxygen atom and one nitrogen atom, oxazoline can be represented by two forms (2) .
Chiral oxazolines especially chiral bis (oxazoline), have been widely applied in many catalytic asymmetric reaction as versatile ligands (3,4) .Oxazoline-base ligands were also found to be effective for the asymmetric addition of diethyl zinc to aldehydes (3,5) .In particular the ligand combining the oxazoline ring and hydroxyl group or an amino group have been reported to show excellent catalytic activity in the asymmetric addition of diethyl zinc to aldehydes (6)(7)(8)(9)(10)(11) .The growing patent literature from the sixties demonstrates that the 1,3,4thiadiazoles are becoming of great interest, this is primarily due to the large number of uses of 1,3,4-thiadiazoles in the most diverse areas, for example in drug synthesis, scintillation materials, dye stuffs industry, photography and corrosion inhibitors.Numerous 1,3,4-thiadiazoles have been synthesized and reported to be biologically versatile compounds having bactericidal, fungicidal, muscle relaxant properties…etc., some 1,3,4-thiadiaozles derivatives possess central nervous system (CNS) depressant activity (12,13) .1,3,4-Oxadiazole is the most thermally stable isomer which has attracted special attention, this is primarily due to the large number of uses in many diverse areas, including drugs, scintillation materials, dyes (14) and surface active agents (15) .The biological significance of oxadiazole ring is well documented in the literature.Thus, it has been shown that many substituted-1,3,4oxadiazoles have biological and medical uses as antibacterial (16) , antifungal (17) , antimalarial (18,19) and anti-inflammatory (20) activities when probably substituted in (2) and ( 5) positions.Further, it was suggested that (-SH) group attached to a heterocyclic nucleus may include fungicidal activity (21) .Instruments 1) Melting points were measured using hot stage Gallen Kamp melting point apparatus and were uncorrected.
2) The F.T.IR spectra in the range (4000-600) cm -1 were recorded using KBr disk on a SHIMADZU F.T.IR 8300 spectrophotometer Japan.
3) Thin Layer Chromatography (TLC) was carried out using Fertigfollen precoated sheets type PolyGram silg, and the plates were developed with iodine vapor.

6-Preparation of 2-thiaacetic acid benzothiazole [6]:
To a stirred solution of (2-MBT) (1.67 g, 0.01 mol) in (25 ml) of ethanol and excess of KOH was added slowly.Chloro acetic acid (0.94 g, 0.01 mol) was added gradually with stirring, the mixture was refluxed for 2 hours after that the mixture was cooled and filtered, the filtrate was poured into ice-water, the crude product was recrystallized from ethanol (24) m.p (228-230 o C), yield (62%).

8-Preparation of 5-amino-2-mercapto-1,3,4thiadiazole [8]:
Potassium hydroxide (2.24 g, 0.04 mol) was dissolved in absolute ethanol (20 ml) and carbon disulfide (4.57g, 3.62 ml, 0.06 mol) was added to the solution.After the addition of carbon disulfide thiosemicarbazide (3.38 g, 0.04 mol) in absolute ethanol (20 ml) was added and the mixture was stirred and refluxed for 6 hours most of the residue was dissolved in water (15 ml) and carefully acidified with concentrated hydrochloric acid (3.5 ml) the precipitate was filtered and washed with cold water and recrystallized from ethanol (25) m.p.

1-Preparation of 2-hydrazino benzothiazole [1]:
2-Mercapto benzothiazole with hydrazine hydrate in ethanol was refluxed for 6 hours to afford the hydrazine benzothiazole [1].The structure of the hydrazine benzothiazole [1]  was confirmed from its melting point and F.T.IR spectrum.The F.T.IR spectrum of compound [1] indicates the disappearance of the thiol bond at (2534.3 cm -1 ) and appearance of doublet bands of NH 2 group asymmetric and symmetric at (3313.5, 3201.6 and ν NH stretching band at 3128.3 cm -1 ).

Preparation of 2-N-benzothiazole-N`-phenyl hydrazine carboxamide [2]:
Compound [2] was synthesized from the reaction of compound [1] with phenyl isocyanate.The compound was characterized by its melting point and F.T.IR spectroscopy.
The F.T.IR spectrum of compound [2]  indicated the disappearance of NH 2 band (3313.5 and (3201.6 cm -1 ) of the starting material and the appearance of N-H band at (3278.8 cm -1 ) and carbonyl group at (1660.6 cm -1 ).

Preparation of 2-N-benzothiazole-N`-1naphthyl hydrazine carboxamide [4]:
Compound [4 was synthesized from the reaction of compound [1] with 1-naphthyl isocyanate.The compound was characterized by its melting point and F.T.IR spectroscopy.The F.T.IR spectrum of compound [4]  indicated the disappearance of NH 2 bands at (3313.5 and 3201.6 cm -1 ) of the starting material and appearance of N-H band at (3261.4 cm -1 ) and carbonyl group band at (1683.6 cm -1 ).

Preparation of 2-thiaacetic acid benzothiazole [6]:
Compound [6] was synthesized from the reaction of 2-mercapto benzothiazole with chloro acetic acid.The compound was characterized by its melting point and F.T.IR spectroscopy.The F.T.IR spectrum of compound [6] indicated the disappearance of S-H band at (2754.2 cm -1 ) and appearance of the carbonyl group band at (1712.4 cm -1 ) of the acid and appearance of O-H group band at (3450 cm -1 ) and C-H aliphatic at (2900 cm -1 ), which displayed broad band in the region (3450.0cm -1 ), and the mechanism of the reaction may be considered as S N 2 mode reaction through the nucleophilic attack of the sulfide anion at the saturated carbon Cl-CH 2 -CO 2 H carrying the leaving group.

Preparation of 2-thiacetyl chloride benzothiazole [7]:
Compound [7] was synthesized from the reaction of 2-thiacetic acid benzothiazole with thionyl chloride.The compound was characterized by its melting point and F.T.IR spectroscopy.The F.T.IR spectrum of compound [7] indicated the disappearance of broad band of O-H at (3450.0 cm -1 ) and appearance of the carbonyl group of the acid chloride at (1730.2 cm -1 ) and C-H aliphatic (2854.4cm -1 ) and (C-Cl) at (758.0 cm -1 ).

Preparation of 5-amino-2-mercapto-1,3,4thiadiazole [8]:
Compound [8] was synthesized from the reaction of carbon disulfide with thiosemicarbazide in ethanol.The compound was characterized by its melting point and F.T.IR spectroscopy.The F.T.IR spectrum of compound [8] indicated the appearance of S-H band at (2773.4 cm -1 ) and NH 2 band asymmetric and symmetric at (3336.6-3251.8cm -1 ) and appearance of thione band at (1342.4 cm -1 ) and N-H band of the tautomerism appeared at (3130.0 cm -1 ).
The F.T.IR spectrum of compound [9] indicated the appearance of N-H band at (3263.3 cm -1 ) and the carbonyl band at (1666.3 cm -1 ) and aromatic (C-H) at (3116.7 cm -1 ) and C-H aliphatic at (2854.4 cm -1 ) and appearance of S-H band at (2525.0 cm -1 ) and appearance of thione band at (1365.5 cm -1 ) and N-H band tautomerism and (N-N) band at (1242.0 cm -1 ) and assume that alkylation step involves S N 2 mechanism.The mechanism of the reaction is shown in Scheme below.The compound was characterized by its melting point and F.T.IR spectroscopy.The F.T.IR spectrum of compound [10] indicated the disappearance of NH 2 bands in benzohydrazine at (3301.9 cm -1 ) and (3201.6 cm -1 ) N-H band at (3147.6 cm -1 ) and disappearance of carbonyl group at (1658.6 cm -1 ) and appearance of C=N band at (1550.6 cm -1 ) and (C-O-C) asymmetric, symmetric at (1242.0 cm -1 ) and (1018.3cm -1 ) and C-H aliphatic at (2854.4 cm -1 ), C-Cl at (856.3 cm - 1 ) and (540.0 cm -1 ).

Microbiological Method
In this work the antimicrobial test was performed according to agar well diffusion method (29) , and selected three concentration for ten derivative compounds as in table (4)  The prepared compound were tested against two pathogenic microorganism, Staphylococcus Aureus (G+) and Proteus vulgaris (G-).In the solidified media ( Nutrient agar ) ,suitable spaced apart holes were made (6 mm in diameter )these holes were filled with (0.1 ml) of prepared compound concentration that dissolve in DMSO(Di Methyl Sulfoxid) after spread the bacteria on agar .These plate were incubated at 37 o C for 24 hour ,the zone of inhibition of bacteria growth around the hole was absorbed and measured in mm and are represented by (R), (Ms) and (S) depending upon the diameter and clarity (30) as in table (5) .The preliminary screening results reveal that the compounds contained (pyrazole, 4thiazolidenin, oxazepine, oxazoline, thiadiazole, oxadiazole, triazole, pyridazine moiety, triazole moiety imino and thiol groups in their structures [1] exhibit the highest antibacterial activity against Proteus vulgaris (G-) while the substituted thiadiazole and triazole compounds showed either low or no activity against both organisms.

Phenylisocyanate
Scheme: Mechanism steps for the preparation of compound[9].