Pyridines are among the most intensively studied heterocyclic compound and their chemistry has been reviewed frequently. Many of the pyridinethiones are biologically active as bactericides [1] [2] evaluated pharmacologically and have been found to show activity against diabetes mellitus, as analagesics and antiinflammants [3] - [6] . On the other hand, pyridothienopyrimidines have been the subject of chemical and biological studies on account of their interesting pharmacological properties. A number of syntheses for substituted derivatives of this triheterocyclic ring system, featuring a variety of pharmacological effects have been developed. Such derivatives have analgesic, [7] antipyretic, [8] antianaphilactic, [9] and anti-inflammatory [10] activity. Also, some are clinically effective antialergic [11] or potentially antineophilactic agent [12] , and a few possess significant hypocholesteromic [13] activity. These assets promoted us to prepare new pyridothienopyrimidines with potential biological activity. So, it has been found that 6-amino-3,5-dicyano-4-methylpyridine-2(1H)-thione 1 [14] reacted with a-halo- ketones and a-halonitriles in ethanol and sodium acetate afforded the S-alkylated derivatives 2. The structure of 2a-m was confirmed by ¹H NMR which showed a singlet signal at d 4.0 ppm corresponding to the active methylene group. Compound 2a-m undergoes cyclization into thienopyridine derivatives 3a-m upon treatment with ethanolic sodium ethoxide. The ¹H NMR of these compounds revealed the disappearance of the methyl group (Scheme 1).

Saponification of the amino ester 3a using alcoholic sodium hydroxide gave the sodium salt of the amino acid 4, which afforded 7-amino-2,9-dimethyl-4-oxo-3H-pyrido[3’,2’:4,5]thieno[3,2-d]oxazine-8-carbonitrile 5 when refluxed in acetic anhydride. Treatment of 5 with ammonium acetate in boiling acetic acid led to the formation of thienopyridopyrimidine derivative 6a. Compound 6a was also obtained by refluxing 3c in acetic anhydride (scheme 2).

On the other hand, when 3a was treated with formamide afforded 7-amino-9-methyl-4-oxo-3H-pyrido [3’,2’: 4,5]thieno[3,2-d]pyrimidine-8-carbonitrile 7. Also 3a was treated with hydrazine hydrate to afford the hydrazide derivative 8. The thiourea derivatives 9 was obtained by reaction of 3a with benzoyl isothiocyante [15] [16] in anhydrous acetone solution. Compound 9 on alkaline cyclization with alcoholic sodium hydroxide give compound 10 instead of 11. The ¹HNMR data of compound 10 revealed the absence of aromatic protons and the mass spectrum was compatible with the molecular formula C₁₁H₇N₅OS₂ (M⁺ = 289). The cyclic amide structure of compound 10 furthermore was defined by comparison its cyclic thioester isomer 12 obtained by ring closure in 98% sulfuric acid at room temperature [17] - [20] . The two isomeric derivatives 10 and 12 are well differentiated according to the alkaline solubility and their ¹HNMR and IR spectra. Acetylation of 3a with acetic anhydride gave the acetyl derivatives 13 that on treatment with aniline afforded 14. Compound 14 was cyclized with 98% sulfuric acid to the pyridothienopyrimidine 15. Treatment of compound 5 with aniline in acetic acid afforded compound 6. The structure of these compounds was confirmed by ¹H NMR, mass, IR spectra and microanalysis (scheme 3).

Most of the synthesized compounds have been tested against four different kinds of bacteria. The result of the antimicrobial studies presented in Table 1. It has been found that the prepared compounds showed antimicrobial

scheme 1. Synthesis of pyridinethione and thienopyridine.

scheme 2. Synthesis of fused pyridine.

scheme 3. Synthesis of pyridothienoazines.

Where: A = Staphyllococcus aurous; B = Streptococcus mitor; C = Esherichia coli; D = Nisseria sica; -- = Negative; + = Poor; + + = Fair; + + + = Good; + + + + = Very good.

activity against Staphylococcus aurous, Streptococcus mitor, Esherichia coli and Nisseria sica.

All melting points are uncorrected and were determined on a Gellankamp apparatus, IR spectra were recorded on Schimadzu 470 spectrophotometer in potassium bromide discs; ¹H NMR spectra were recorded on a Varian EM-390 (90 Mhz) spectrophotometer using TMS as an internal standard, mass spectrometer MS 30 (AEL) at 70 ev. Analytical data were obtained from the microanalytical data center at Cairo University.

It was prepared according to a liturature procedure [14] .

To a solution of mercaptopyridine 1 (0.01 mol) in ethanol (30 ml) and sodium acetate (0.01 mol), the appropriate halocompound (0.01 mol) was added. The reaction mixture was refluxed for 1 h. After cooling, the solid product formed was collected by filtration, washed with water several times and recrystallized from the appropriate solvent. The physical data (c.f. Table 2 and Table 3).

To a solution of compound 2 (2 g) in absolute ethanol (30 ml), a few drops of sodium ethoxide was added and refluxed for 1 hour. After cooling the solid product formed was collected by filtration and recrystallized from the appropriate solvent.

The amino ester 3a was refluxed for 3 h in ethanolic sodium hydroxide (30 ml 10%). The solid product obtained after cooling was collected by filtration, washed was ethanol and left to dry. This compound was used as such in the next procedure.

The sodium salt 4 (0.5 g) was refluxed in acetic anhydride (30 ml) for 3 h. The reaction mixture was left to stand at room temperature and the solid product formed was filtered off and recrystallized from dioxan; mp 210˚C; yield 40%; IR n cm⁻¹ 3330 - 3200 (NH₂), 2190 (CN), 1700 (CO); MS, m/z = 272; Found: C, 53.0; H, 3.0; N, 20.8; S, 11.77; calcd for C₁₂H₈N₄O₂S: C, 52.94; H, 2.96; N, 20.58; S, 11.9%.

A mixture of oxazine derivative 5 (0.01 mol) and ammonium acetate (0.02 mol) or aniline (0.01 mol) in acetic acid (30 mol) was heated under reflux for 3h. The solid product formed after cooling was collected by filtration and recrystallized from the appropriate solvent.

Compound 6b was crystallized from DMF/Dioxan as yellow crystals; yield 45%; mp > 360˚C; IR n cm⁻¹ 3355 - 3220 (NH₂); 3220 - 3150 (NH); 2200 (CN); 1655 (CO); Found: C, 62.5; H, 3.9: N, 20.3; calcd for C₁₈H₁₃N₅OS: C, 62.23; H, 3.77; N, 20.16%.

To a solution of 3a (0.01 mol) in ethanol (30 ml), the hydrazine hydrate (0.02 mol) was added. The reaction mixture was refluxed for 3 h. The solid product formed was collected by filtration and recrystallized from DMF/Dioxan as white crystals; yield 66%; mp 295˚C; IR n cm⁻¹ 3400 - 3220 (NH₂); 3220 - 3100 (NH); 2195 (CN); 1650 (CO); MS: m/z = 262; Found: C, 45.9; H, 3.7; N, 32.5; S, 12.4; calcd for C₁₀H₁₀N₆OS: C, 54.79; H, 3.84; N, 32.04; S, 12.22%.

To a solution of 3a in anhydrous acetone, benzoyl isothiocyanate (prepared in situ by refluxed mixture of benzoyl chloride (0.1 mol) and ammonium thiocyanate (0.1 mol) in anhydrous acetone for ten minutes) was added. The reaction mixture was refluxed for 3 hours, then poured onto cold water. The precipitate was collected by filtration, repeatedly washed with cold water and recrystallized from ethanol as orange crystals; yield 50% mp 145˚C - 150˚C; IR n cm⁻¹ 3340 - 3200 (NH₂-NH); 2190 (CN); 1780 (CO) ester; 1650 (CO); MS: m/z = 439; Found: C, 55.9; H, 3.9; H, 15.0; S, 15.1; calcd for C₂₀H₁₇N₅O₃S₂: C, 54.66; H, 3.87; N, 15.94; S, 14.59%.

A sample of compound 9 (1 g) was dissolved in 2N ethanolic sodium hydroxid solution (30 ml) and refluxed for 6 h. The reaction mixture was poured onto ice/water and acidified with 10% HCl. The solid formed was collected by filtration and recrystallized from DMF/water as brown crystals; yield 66%; mp > 350˚C; IR v cm⁻¹ 3300 - 3200 (NH₂); 2200 (CN); 1640 (CO); MS: m/z = 289; Found: C, 45.8; H, 2.5; N, 25.0; s, 22.4; calcd for C₁₁H₇N₅OS₂: C, 45.67; H, 2.42; N, 24.22; 22.16%.

A solution of compound 9 or 14 (1 g) in 98% sulfuric acid (5 ml) was stirred 1 h. then left at room temperature for 5 days. The solid product formed after pouring the clear solution in ice water (100 ml) was collected, wash with water, dried and recrystalized from the appropriate solvents.

Compound 12 was obtained as brown crystals from DMF/water; mp > 350˚C; yield 30%; IR v cm⁻¹ 3375 - 3270 (NH₂), 2220 (CN), 1662 (CO); Found: C, 45.9; H, 2.6; N, 24.4; calcd for C₁₁H₇N₅OS₂: C, 45.67; H, 2.42; N, 24.22%.

To a solution of compound 9 (0.01 mol) in acetic acid (30 ml), the appropriate of acetic anhydride (3 ml) was added. The reaction mixture was heated under reflux for 3 h. The solid product formed after cooling was collected by filtration and recrystallization from methanol as orange crystal. mp 330˚C; yield 60%; IR v cm⁻¹ 3330 - 3150 (2NH), 2200 (CN), 1724 (CO ester), 1641(CO)); ¹H NMR (DMSO-d6) d = 1.4 (s, 3H, CH₃); 2.4 (s, 3H, CH₃); 2.4 (br, 6H, 2CH₃); 4.4 (q, 2H, CH₂); 8.4 (br, 2H, 2NH); Found: C, 53.5; H, 4.8; N, 15.8; S, 9.2; calcd for C₁₆H₁₆N₄O₄S: C, 53.32; H, 4.47; N, 15.55; S, 8.90%.

To a solution of compound 13 (0.01 mol) in ethanol (30 ml) the appropriate of aniline (0.01 mol) was added, the reaction mixture was heated under reflux for 3 h. The solid product formed after cooling was collected by filtra- tion and recrystallized from acetic acid as yellow crystals; mp > 350˚C; yield 50%; IR v cm⁻¹ 3450 - 3195 (NH), 2220 (CN), 1670 (CO); ¹H NMR (DMSO-d6) d = 2.3 (s, 3H, CH₃); 2.8 (d, 6H, 2CH₃); 8.2 (s, 1H, NH); 4.2 - 4.6 (m, 5H, Ar-H); 8.4 (br, 1H, NH); 10.4 (s, 1H, NH); MS: m/z = 407; Found: 86.1; H, 4.4; N, 17.4: S, 8.0; calcd for C₂₀H₁₇N₅O₃S: C, 85.96; H, 4.21; N, 17.19; S, 7.87%.

Compound 15 was obtained as yellow crystals from dioxan; mp > 350˚C; yield 30%; IR v cm⁻¹ 3330 (NH), 2210 (CN), 1693 (2CO); MS: m/z = 389; Found: 61.9; H, 3.9; N, 18.1; S, 18.3; calcd for C₂₀H₁₅N₅O₂S: C, 61.68; H, 3.88; N, 17.98; S, 8.23%.

The newly synthesized compounds were dissolved in propylene glycol (10 mg/20ml) and transferred to a filter paper disc (10 mm) diffusion plate method [18] . The bacterial suspension was prepared by adding 20 ml of dis- tilled water to 10-d-old cultures of the test bacteria grown on a nutrient agar of NA. The spore suspension was prepared by adding 20 ml of distilled water to 10-d-od cultures of the test bacteria.

Abdel Haleem Mostafa Hussein,Essam Abdel Raheem Eshak,Fathi Aly Abu-Shanab, (2015) Nitriles in Heterocyclic Synthesis: Synthesis of Pyrido[3’,2’:4,5]Thieno[2,3-d] Pyrimidines Derivative. Open Access Library Journal,02,1-9. doi: 10.4236/oalib.1101307