Synthesis of Some Novel Thieno [ 2 , 3-d ] pyrimidines and their Antibacterial Activity

Bromination of intermediate 1-[4-(6, 7-dihydro-5H-cyclopenta [4, 5] thieno[2, 3-d]pyrimidin-4-yl amino) phenyl] ethanone (4) yielded (5). Which upon reaction with different substituted benzothiazoles give a novel series of pyrimidine [6(a-g)]. However reaction of (5) with 4-chloro-2-triflouro acetyl aniline provided (6h). Similarly reaction of (5) with 5-amino tetrazole & 2-amino benzimidazole produced (6i) & (6j) respectively. All the synthesized compounds were tested against bacteria (Gram positive and Gram negative).


Introduction
Antibiotics have revolutionized the medical care in the 20 th century.With the discovery of antibiotics people were convinced that infectious diseases might some day be wiped out.Diseases that were once life threatening, such as pneumonia, had become curable.The success of antibiotics in therapy related fields has made them one of the most important products of the drug industry today 1 .However, the emergence of superbugs i.e. bacteria that resist the effects of the most powerful antibiotics are posing a great challenge to the field of medicines.Thus scientists are working to find new ways to defeat bacteria that are increasingly resistant to the antibiotics already available 2 .It is well known that pyrimidine and fused heterocyclic pyrimidine derivatives are of great biological interest, especially as antiviral, antitumor and antimicrobial agents [3][4][5][6][7][8][9][10][11][12][13][14] .Also, the rapid growth in the literature dealing with the synthesis and biological activity of the thienopyrimidine derivatives prompted us to synthesize new derivatives of fused pyrimidine, and thieno [2,3-d]pyrimidine derivatives.Aromatic and heteroaromatic compounds are useful substrates for the preparation of various condensed pyrimidine heterocyclic systems 15 .In this present work, interest is expressed in synthesizing (Scheme 1) some new thieno [2, 3-d]pyrimidine derivatives (6a-g), (6h), (6i) & (6j) and are evaluated for their antimicrobial activity. (3) Where R= H, Cl, OMe, CH3, F, COOC2H5, NO2 Scheme 1.

Experimental
Melting points ( o C, uncorrected) were recorded on an Electro thermal I A 9100 Digital Melting Point Apparatus.IR spectra (ν max in cm -1 ) were recorded on a Shimadzu FT-IR 8300 Spectrophotometer using KBr pellets technique. 1H NMR Spectra were recorded using Bruker WM-400 spectrophotometer using DMSO-d 6 or CDCl 3 as the solvent and TMS as the internal reference (Chemical Shifts in ppm).TLC using silica gel G60 (Merck, Germany) routinely checked the purity of the compounds and the spots were exposed in iodine vapour for visualization. 16clopentanone (0.1 mol, 8.4 g), cyanoacetamide 17 (0.01 mol, 0.84 g), sulphur powder (0.01 mol, 0.32 g) and diethyl amine (10 mL) in absolute ethanol (30 mL) was stirred in a round bottomed flask for 3 h.After the completion of the reaction time the mixture was poured on crushed ice.The separated solid was filtered, washed with water and recrystallized from alcohol to furnish compound (1) 3, 5, 6, 7-Tetrahydro-4H-cyclopenta [4, 5]thieno [2,3-d]pyrimidin-4-one (2)   The compound (1) was heated with formamide 20 mL in a round bottomed flask in an oil bath at 60 ο C. The temperature was then gradually raised.The reaction mixture gets dissolved completely with the formation of brown solution at 110 ο C. The temperature of the oil bath was raised to 180-200 ο C, when the reaction mixture was heated at this temperature for 3 h.After, the completion of the reaction, reaction mixture was allowed to cool at room temperature.The product separated as yellow needles was collected by filtration and washed with water several times and finally with 25 mL of acetone and then dried.4-Chloro-6, 7-dihydro-5H-cyclopenta [4, 5]thieno [2, 3-d]

Antimicrobial Activity 18
The antimicrobial activity of representative new compounds (6a-g), (6h), (6i) & (6j) was investigated against a variety of microorganisms, including the gram positive bacteria Bacillus subtilis, Bacillus pumilis and Staphylococcus aureus, Escherichia coli the gramnegative bacteria.Antimicrobial activity was determined by the disc diffusion method

Sample preparation
Sterilized filter paper discs (6 mm in diameter) were wetted with 10 µL each of a solution of the tested compound (50 µg & 100 µg/mL of the compound in DMF).The discs were then allowed to dry and placed on the surface of agar plates seeded with the test organism.

Medium inoculation and cultivation condition
Each plate contained 15 mL of the agar medium, previously seeded with 0.2 mL of an 18 h old broth culture of each organism.The inoculated plates were incubated at 37 o C for 48 h with the test discs in place and the inhibition zones were measured in mm.Discs impregnated with DMF were used as controls.The antibacterial reference ampicillin discs tested as standard.

Table 2 .
Antibacterial activity of synthesized compounds.