Research Journal of Chemical Sciences ______________________________________________ ISSN 2231-606X Vol. 5(7), 8-11, July (2015) Res. J. Chem. Sci. International Science Congress Association 8 A Novel Bromonaphthyl Based 2-Amino-1,3-Thiazines: Synthesis, Characterization with Invitro Antimicrobial ScreeningPrakash N, Sivagami S and Ingarsal N* PG and Research Department of Chemistry, Rajah Serfoji Govt. College, Thanjavur-613 005, Tamilnadu, INDIAAvailable online at: www.isca.in, www.isca.me Received 16th June 2015, revised 23rd June 2015, accepted 15th July 2015 AbstractA clinically important substrate of bromosubstituted acetylnaphthalene was used as the precursor for the preparation of a series of 1-(2-bromonaphthalen-6-yl)-3-phenylprop-2-en-1-ones. The formed unsaturated ketones on treatment with thiourea in the presence of base like KOH in alcohol yields corresponding 4-(2-bromonaphthalen-6-yl)-6-phenyl-6H-1,3-thiazin-2-amine. The synthesized thiazines are evaluated their structure on the basis of NMR, MASS, IR and Elemental analyses along with their physical data. The antibacterial and antifungal activities indicate some of these thiazines are potential antimicrobial agents. Keywords: Synthesis, bromonaphthalene, 2-amino-1,3-thiazines, characterization, antimicrobial screening. Introduction Thiazine core having great interest in recent years especially in synthetic drug formulation in vowing with their proved biological activities. Aminothiazines with amino group occupying the position in between two hetero atoms are important synthetic target as well as building block of various heterocycles. These substituted 2-amino-1,3-thiazines are proved to be very potent antimicrobial, antiinflammatory, antihypertensive, calcium channel blocker etc. Bioactive molecules with bromo substitution are key intermediates for the synthesis of biologically active molecules and are antimicrobials. The amino thiazines are synthesised from various methods especially from chalcones. The chalcones are -unsaturated ketones posses a wide range of biological activities such as antibacterial, antiviral, analgesic etc8,9. In addition with these observations, the substituted naphthalenes show a variety of biological activities such as antitumour10, antifungal11 etc. By focusing the importance of aminothiazines, substituted naphthalenes and bromo substitutions, along with our earlier work extension, we wish to synthesize the hybrid molecule of thiazine comprising with bromosubstituted naphthalene moiety. Material and Methods All the chemicals were analytical grade and solvents were distilled before use. Melting points of all the synthesized compounds were determined in open capillary tubes on an electrothermal apparatus and are uncorrected. The purity of the compounds was checked by TLC using silica gel G. The IR spectra were recorded on SHIMADZU FT-IR spectrometer using KBr pellet. The H and 13C NMR spectra were recorded on Bruker (AMX-400 MHz) using CDCl3 as solvent and TMS as an internal standard (chemical shifts in ppm). Mass spectra were recorded on CLASS-5000 Mass spectrometer and elemental analyses were done on vario EL.CHNO elemental analyser. Procedure for preparation of 1-(2- bromonaphthalen-6-yl)ethanone: The titled compound was prepared by the acetylation of 2-bromonaphthalene using acetylchloride in nitrobenzene in the presence of anhydrous aluminium chloride12. General procedure for preparation of 1-(2-bromonaphthalen-6-yl)-3-aryl prop-2-en-1-ones 3a-e: Quantitative amounts of substituted aromatic aldehyde (0.02 mol) and 1-(2-bromonaphthalen-6-yl)ethanone (0.02 mol) in ethanol (50 mL),were heated over a water bath while a solution of sodium hydroxide (1.5g in 5mL of water) was added slowly during 15 minutes and the heating was continued for further 15 minutes. The solution was cooled, filtered the product and recrystallised from ethanol. General procedure for preparation of 2-amino-4-(2-bromonaphthalen-6-yl)- 6-aryl-6H-1,3-thiazines 4a-e: A solution containing 1-(2-bromonaphthalen-6-yl)-3-arylprop-2-en-1-one (0.01mol), thiourea (0.01 mol) and KOH (0.02 mol) in ethanol (50 mL) was refluxed for 4-5 hours and the reaction was monitored by TLC. After completion of the reaction, one third of the solvent was removed under reduced pressure, cooled to room temperature, poured to ice cold water and filtered the solid product.The pure 1,3-thiazines were obtained by column chromatographic technique using benzene-ethyl acetate as eluting solvent. 2-amino-4-(2-bromonaphthalen-6-yl)-6-phenyl-6H-1,3-thiazine 4a: Yield: 78%, M.PºC: 135; IR (KBr, cm-1) 3351, Research Journal of Chemical Sciences ___________________________________________________________ ISSN 2231-606XVol. 5(7), 8-11, July (2015) Res. J. Chem. Sci. International Science Congress Association 9 1525, 1362, 1285, 667 H NMR, (, ppm): 4.24 (dd, 1H, J1,2= 5.5Hz,J1,3= 8Hz), 4.67 (dd, 1H, J1,2= 2Hz,J1,3= 14Hz), 8.42 (s, 1H), 8.46 (s, 1H) and 7.28-8.60 (m, 11H), 13C NMR (, ppm): 45.01 (C-6), 106.60 (C-5), 134.80 (C-4), 167.77 (C-NH) 122.85-134.73 (Ar-C). 2-amino-4-(2-bromonaphthalen-6-yl)-6-(2-chlorophenyl)-6H-1,3-thiazine 4b: Yield: 80%, M.PºC: 140; IR (KBr, cm-1) 3404, 1558, 1382, 1350, 669; H NMR, (, ppm): 5.46 (dd, 1H, 1,2= 2Hz,J1,3= 4Hz), 5.79 (dd, 1H, J1,2= 2 Hz,J1,3= 4 Hz), 7.87 (s, 1H), 7.90 (s, 1H) and 7.26-8.0 (m, 10H), H NMR (DO) 5.49 (d, 1H), 5.80 (d, 1H) 7.87 and 7.90 signals disappeared. 13C NMR (, ppm): 53.70 (C-6), 99.49 (C-5), 138.89 (C-4), 176.13 (C-NH) 121.26-134.61 (Ar-C). Mass: m/z 429(M), 431(M+2). 2-amino-4-(2-bromonaphthalen-6-yl)-6-(4-methoxyphenyl)-6H-1,3- thiazine 4c: Yield: 84%, M.PºC: 120; IR (KBr, cm-1) 3320, 1531, 1389, 1315, 680; H NMR, (, ppm): 5.29 (dd, 1H, 1,2= 1Hz,J1,3= 3.5Hz), 5.34 (dd, 1H, J1,2= 1Hz,J1,3= 3.5Hz), 7.88 (s, 1H), 7.90 (s, 1H) and 6.90-8.01 (m, 10H), H NMR (DO) 5.33 (d, 1H), 5.29 (d, 1H) 7.88 and 7.90 signals disappeared. 13C NMR (, ppm): 56.81(C-6), 101.80 (C-5), 134.53 (C-4), 175.21 (C-NH) 121.13-134.38 (Ar-C) 55.39 (O-CH). Mass: m/z 424(M), 426(M+2). 2-amino-4-(2-bromonaphthalen-6-yl)-6-(4-methylphenyl)-6H-1,3-thiazine 4d: Yield: 75%, M.PºC: 145; IR (KBr, cm-1) 3327, 1566, 1350, 1274, 651; H NMR, (, ppm): 5.28 (broad s, 2H), 8.01 (s, 1H), 8.02 (s, 1H) and 7.28-8.55 (m, 10H). 13C NMR (, ppm): 52.00 (C-6), 104.15 (C-5), 135.54 (C-4), 166.33 (C-NH), 121.24-135.36 (Ar-C), 21.44 (Ar-CH). 2-amino-4-(2-bromonaphthalen-6-yl)-6-(4-bromophenyl)-6H-1,3-thiazine 4e: Yield: 79%, M.PºC: 132; IR (KBr, cm-1) 3396, 1560, 1327, 1273, 671; H NMR, (, ppm):5.48 (dd, 1H, 1,2= 2.5Hz,J1,3= 4.5Hz), 5.77 (dd, 1H, J1,2= 2Hz,J1,3=4.5Hz), 8.01 (broad s, 2H), and 7.01-7.89 (m, 10H). 13C NMR (, ppm): 56.06 (C-6), 99.65 (C-5), 134.59 (C-4), 176.00 (C-NH), 121.24-134.46 (Ar-C). Antimicrobial activity: The synthesized compounds (4a-ewere screened for their invitro antimicrobial activity by using Mueller-Hinton broth method. Antibacterial activities were screened against three gram positive bacterias (Bacillus subtillis, staphylococcus aureus and streptococcus pyogenes) and three gram negative bacterias (Escherichia coli, Klebsiella pneumoniae and pseudomonas aeruginosa). Antifungal activities were screened against Aspergillus flavus, Aspergillus niger and Penicillium chrysogenum. Both antibacterial and antifungal activities were studied by measuring the zone of inhibition on agar plates at concentration 10µg/mL and reported in table-1.Ciprofloxacin used as the standard for antibacterial and amphotericin-B used as the standard for antifungal activities respectively. Results and Discussion The Friedal-Crafts acylation of 2-bromonaphthalene in the presence of a Lewis acid like anhydrous aluminium chloride in nitrobenzene affords 2-acetyl-6-bromonaphthalene and 1-acetyl-7-bromonaphthalene. The 2-acetyl-6-bromonaphthalene is purified by using literature method and undergoes Claisen-Schmidt condensation with equal molar ratio of substituted aromatic aldehydes in the presence of alkali metal hydroxides gives corresponding 1-(2-bromonaphthalen-6-yl)-3-arylprop-2-en-1-ones (3a-e). On further treatment of (3) with thiourea at reflux in ethanol containing potassium hydroxide gives the bromonaphthylthiazine derivatives (4a-e) (scheme-1). The formation of thiazine follows the Michael type addition of thiourea to -unsaturated ketone and cyclisation. The NMR spectra of all the synthesized compounds are confirmed the structure of thiazine in addition with the evidences obtained from IR, Mass and Elemental analyses (table-2). The physical parameters like TLC and Melting points (table-2) of synthesized compounds are quite different from starting materials also support the thiazine formation. The compounds were evaluated for their antimicrobial activity. Most of the compounds exhibit good to moderate antibacterial and antifungal activities against the tested micro organisms. The compounds 4a and 4c shows better antifungal activity than the standard amphotericin-B against Aspergillus flavus, Penicillium chrysogenum and Aspergillus niger while the remaining compounds are inactive against fungi. All the synthesized compounds are active against gram positive as well as gram negative bacterias but the antibacterial activity of these compounds are less and moderate as compared to standard Ciprofloxacin. Among these thiazines, the thiazines 4c and 4e shows slightly higher activity against gram positive bacterias. Among all bacterias, the compounds are more active against Klebsiella pneumoniae. The H NMR spectra of compounds 4a-e, having the characteristic signal for amino protons at the chemical shift value (, ppm) of 7.8-8.5 as two singlets for two protons. This separate signals arising due to the different orientation of amino protons with different hetero atoms viz. nitrogen and sulphur and this is confirmed by the addition of DO, results the disappearance of respective peaks at particular chemical shift values. The H-5 and H-6 protons are resonates in the aliphatic region with chemical shift values from 4.24-5.79 ppm as two separate doublet of doublets. These protons are undergoes long range coupling with nearest amino proton results doublet of doublets (J1,2= 3.0 Hz and J1,3= &#x-3.3;女 3.5 Hz ) (or) broad signals. The influence of amino protons in long rang coupling is confirmed by the reduced multiplicity of H-5 and H-6 protons as doublets instead of doublet of doublet or broad signals with the addition of DO. The aromatic protons show their characteristic multiplets in the regions of 6.9-8.6 ppm. Research Journal of Chemical Sciences ___________________________________________________________ ISSN 2231-606XVol. 5(7), 8-11, July (2015) Res. J. Chem. Sci. International Science Congress Association 10 Table-1 Antimicrobial activities of compounds 4a-e (Diameter of inhibition in mm) Compounds Gram Positive Bacteria Gram negative Bacteria Fungi A B C D E F G H I Standard 16 21 17 20 19 22 11 10 11 Control - - - - - - - - - 4a 9 9 10 7 10 8 18 19 13 4b 8 9 11 9 12 8 - - - 4c 13 10 8 7 11 12 15 11 14 4d 11 8 8 9 12 9 - - - 4e 8 11 9 8 8 8 - - - A-Bacillus Subtillis, B-Staphylococcus aureus, C-Streptococcus pyogens, D-Escherichia coli, E-Klebsiella pneumoniae, F-Pseudomonas aeruginosa, G-Aspergillus flavus, H-Aspergillus niger. I-Penicilliumchrysogenum Scheme-1 Formation of ThiazineTable-2 Physical and analytical data of 4a-e Compounds Melting Point (ºC) Yield (%) Molecular Formula Elemental Analysis Carbon found (Cal cd) % Hydrogen found (Cal cd) % Nitrogen found (Cal cd) % 4a 135 78 C 20 H 15 BrN 2 S 60.76 (60.92) 3.79(3.92) 7.08(7.19) 4b 140 80 C 20 H 14 BrN 2 SCl 55.94 (55.99) 3.26(3.33) 6.52(6.66) 4c 120 84 C 21 H 17 BrN 2 SO 59.29 (59.62) 4.00(4.18) 6.58(6.72) 4d 145 75 C 21 H 17 BrN 2 S 61.61 (61.82) 4.15(4.31) 6.84(6.97) 4e 132 79 C 20 H 14 Br 2 N 2 S 50.63 (50.77) 2.95(2.81) 5.90(5.99) *The values within the paranthesis are calculated value. The 13C NMR displays characteristic peaks at (, ppm) 45-56 (C-6), 99-106 (C-5), 134-138 (C-4), 166-176 (C-NH), 121-135 (C-Ar). The IR spectra of compounds shows the characteristic bands (cm-1) corresponding -C-Br stretching (650-700), C=N stretching (1550-1570), -C-NH stretching (1300-1400), -NH stretching (3300-3500) and -C-S stretching (1200-1400). The Mass spectra of compounds 4b and 4c shows the corresponding fragmented ions and molecular ion peaks, M+ (424 and 429), +2 (426 and 431). ConclusionIn the present work, we have synthesized a series of 2-amino-4-(2-bromonapthalen-6-yl)-6-phenyl-6H-1,3-thiazines from the corresponding 1-(2-bromonapthalen-6-yl)-3-arylprop-2-en-1-ones and evaluated their antibacterial and antifungal activities in invitro conditions. The synthesized compounds are Research Journal of Chemical Sciences ___________________________________________________________ ISSN 2231-606XVol. 5(7), 8-11, July (2015) Res. J. Chem. Sci. International Science Congress Association 11 characterised by using spectral (IR, NMR and Mass), elemental and physical (Melting points and TLC) techniques. References 1.Saranya A.V., Ravi S and Venkatachalapathi S., Invitro antioxidant activity of diethyl malonate adducts of phenothiazine, Res. J. Chem. 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