Quinazoline (1) is a fused six-member aromatic ring (a benzene ring and a pyrimidine ring are fused). Quinazoline is a fused bicyclic compound earlier known as benzo-1, 3-diazine. It was first prepared in the laboratory in 1903 by Gabriel [1]. Although its derivative were known much earlier. The name quinazoline (German: Chinazolin) was first proposed for this compound by weddige on observing that this was isomeric with the compounds cinnoline and quinoxaline. Paal and Bush suggested the numbering of quinazoline ring system, which is currently used [2-4]. The other less commonly used names for this ring system are ‘phenmiazine’ and 5, 6-benzopyrimidine. However, the name quinazoline is now universally accepted (Figure 1).

Figure 1: Quinazoline.

Quinazoline derivatives, which belong to the N-containing heterocyclic compounds, have caused universal concerns due to their widely and distinct biopharmaceutical activities. Researchers have already determined many therapeutic activities of quinazoline derivatives, including anti-cancer [5-8], anti-inflammation [9,10], antibacterial [11-14], analgesia [9,13], anti-virus [15], anti-cytotoxin [16], anti-spasm [13,17], anti-tuberculosis [18], anti-oxidation [19], anti malarial [20], anti-hypertension [21], anti-obesity [22], anti-psychotic [23], anti-diabetes [24], etc. Medicinal chemists synthesized a variety of quinazoline compounds with different biological activities by installing various active groups to the quinazoline moiety using developing synthetic methods. And the potential applications of the quinazoline derivatives in fields of biology, pesticides and medicine have also been explored.

Quinazoline derivatives have attracted much attention for their various biological and medicinal properties. For example, they act as the potent tyrosine kinase and cellular phosphorylation inhibitors [25], and they are also used as ligands for benzodiazepine and GABA receptors in the central nervous system (CNS) [26] or as DNA binders [27-29] Some of them show remarkable activity as anticancer [30], antiviral [31] and antitubercular agents [32,33]. Molecules containing the Quinazoline unit have been popular drugs. For example, Erlotinib is used in the treatment of several types of tumors [34] Prazosin acts as an R-adrenergic blocker [35] and Iressa as an epidermal growth factor receptor inhibitor was approved by the Food and Drug Administration in USA for the treatment of lung cancer [36].

The Quinazoline skeleton is present in a variety of biologically active compounds, among these are several marketed drugs such as prazosin (1), Gefitinib (2), Erlotinib (3), Vandetanib (4) (Figure 2).

Figure 2: Quanazoline skeleton is present in a biologically active compounds.

Encouraged by the diverse biological activities of Quinazoline Heterocyclic compounds, it was decided to prepare a new series of Quinazoline derivatives. Literature survey revealed that incorporation of different groups in Quinazoline Heterocyclic ring enhanced antibacterial and antifungal activity. In the present communication 2,4 Di Chloro Quinazoline (3) was reacted with meta-Amine Sulphonamide (4) in tert-butanol at 90°C to form Compound (5), which was further reacted with aqueous ammonia in THF(Tetra Hydro Furan) at 90°C to get target compound (6), Which was further reacted with different boronic acids under Chan-Lam reaction conditions to form Target compounds (8a-8j). The synthesis of the compounds as per the following Figure 3 given below.

Figure 3: Structure of 2,4 di hydroxy Quinazoline (compound 2).

The structures of all synthesized compounds were assigned on the basis of IR, Mass, ¹H and ¹³C NMR spectral data analysis. Further these compounds were subjected for antifungal and antibacterial activity.

In this Investigation chemicals were purchased from local dealer with S.D fine make was used. Chemicals were 99% pure; purity has been checked by Thin layer chromatography and melting point. Conventional method has been used for synthesis of Quinazoline derivatives. Stirring and reflux method were used for synthesis of Quinazoline derivatives 8(a-j) respectively. The Nomenclature was given for Synthetic compounds from compound (1) to Compounds 8a-8j by using Chem Bio draw Ultra -12 version.

The title compounds 8 (a-j) were synthesized in Seven steps using different reagents and reaction conditions, the 8 (a-j) were obtained in moderate yields. The structure were established by spectral (IR, ¹H-NMR, ¹³C-NMR and mass) and analytical data (Scheme 1).

Scheme 1: Synthetic path way for compounds 8a-8j.

General procedure for synthesis of 2,4 di hydroxy Quinazoline [compound (2)]

A mixture of 2-aminobenzoic acid (1) (50 g, 0.364 mole) and urea (109.2 gms, 1.82 mol) was heated at 180°C for 3 h. upon cooling to 120°C, The reaction mixture was poured into sodium hydroxide (1000 mL, 1N) solution and any insoluble material removed by filtration. The mixture was then acidified with HCl (2N), to yield 2,4 di hydroxy Quinazoline (compound 2) F as a white precipitate, which was collected by filtration and dried. (95% yield, 56 gms).

Yield: 90%; M.p. above 300°C (Figures 4-8);

Figure 4: ¹H NMR Spectra of 2,4 di hydroxy Quinazoline (Compound 2).

Figure 5: ¹H NMR Spectra Splitting pattern of 2,4 di hydroxy Quinazoline (compound 2).

Figure 6: IR Spectra of 2,4 di hydroxy Quinazoline (compound 2).

Figure 7: LCMS Data of 2,4 di hydroxy Quinazoline (compound 2).

Figure 8: LCMS-Mass Spectra Data of 2,4 di hydroxy Quinazoline (compound 2).

¹H NMR (DMSO-d₆) δ ppm 7.15 (t, 2H, Ar-H), 7.6 (t, ¹H, Ar-H), 7.85 (d, ¹H, Ar-H), 11.05(¹H,S), 11.1 (¹H,S).

¹³C NMR (DMSO-d₆) (δ/ppm): 120 (Ar C-H), 125.6 (Ar C-H),133.5(Ar C-H), 126.6(Ar C-H), 185(Ar C-OH),187(Ar C-OH), 110(Ar C), 151 (Ar C).

IR (KBr, ν/cm^–1): 3428 (OH, broad), 3079 (Ar C-H), 1604 (C=N); LCMS Data shows That 2, 4 di hydroxy Quinazoline [Compound 2] Purity of 99.63%, RT 1.924, Mass 161.1 [M+, 100%].

General procedure for synthesis of 2, 4 di chloro Quinazoline [compound (3)]

A mixture of quinazoline-2,4-diol(compound 2) (55 gms, 0.339 mol), Phosphorous oxy chloride (550 mL), and catalytic amount of DMF (2 ml) was heated at reflux for 8 hrs, and the reaction was monitored by TLC. The reaction mixture was concentrated under reduced pressure and the residue was poured onto ice water with vigorous stirring yielding a precipitate. The mixture was then filtered to yield 2, 4 di chloro Quinazoline (compound 3) (Figure 9) as a white solid.

Figure 9: Structure of 2,4 di chloro Quinazoline (Compound 3).

Yield: 75% (51 gms).

M.p. 116-118°C;

¹H NMR (CDCl₃-d₁) δ ppm 8.30-8.20 (d, IH), 8.10-8.00 (m, 2H), 7.80-7.70 (d, I H) (Figures 10 and 11).

Figure 10: ¹H NMR Spectra of 2,4 di chloro Quinazoline (Compound 3).

Figure 11: ¹H NMR Spectra Splitting pattern of 2,4 di chloro Quinazoline (Compound 3).

³C NMR (CDCl₃-d₁) (δ/ppm): 120(Ar C), 125 (Ar C), 128.6 (Ar C),136.5(Ar C), 151 (Ar C), 157(Ar C), 161.3(Ar C-) (Figures 12 and 13).

Figure 12: LCMS Data of 2,4 di chloro Quinazoline (Compound 3).

Figure 13: LCMS-Mass spectral Data of 2,4 di chloro Quinazoline (Compound 3).

IR (KBr, ν/cm^–1): 755 (C-Cl), 3040 (Ar C-H), 1619 (C=N);

GCMS Purity 89.75%, RT 8.738, Mass 198 [M⁺], 200 [M+2], 202 [M+4], 9:6:1 It indicates molecule contains Two chlorine atoms and Even no. of Nitrogen atoms According to Nitrogen rule.

General procedure for synthesis of 4-(2-chloroquinazolin-4- yl) thiomorpholine [Compound 5]

To the mixture of 2,4 di chloro Quinazoline (Compound 3) (10 gms, 0.0505 mol), Na₂CO₃ (0.1262 mol,13.5 gms) and MeOH (100 mL), Thiomorpholine (2.1 eq, 0.106 mol, 10.93 gms), was added drop wise at 0°C. Then the reaction mixture was Stirred at Room Temperature for 3 hrs. After completion of reaction as indicated by TLC, the reaction mixture was concentrated under reduced pressure and the residue was poured onto ice water with vigorous stirring yielding a precipitate. The precipitate was then filtered to yield the title compound (Compound 5) (Figure 14) as a white solid (12.85 g, 96% yield).

Figure 14: Structure of 4-(2-chloroquinazolin-4-yl) thiomorpholine (Compound 5).

M.p. 226-227°C.

ESI-MS m/z 266 [M+H]⁺, 288[M+Na]⁺

¹H NMR (400 MHz, DMSO-d₆) δ ppm 2.7 (4H, t, 2 × CH₂–S), 3.5 (4H, t, 2 × CH₂–N), 7.6 (¹H,t, Ar-H), 7.85 (2H,m, Ar-H), 8.2 (¹H,d, Ar-H).

¹³C NMR (100 MHz, DMSO-d₆) (δ/ppm): 28(2C, C-S), 53(2C, C-O), 120, 123, 128, 132, 135, 153, 158, 181.

IR (KBr, ν/cm^–1): 748 (C-Cl), 3040 (Ar C-H), 1629 (C=N);

General procedure for synthesis of 4-thiomorpholinoquinazolin- 2-amine [Compound 6]

A solution of aqueous ammonia (NH₃.H₂O, 2.5 mol, 88 mL.), and compound (5) (0.039 mol, 10.335 g.) was stirred at 90°C for 6 hrs. The precipitate was collected by filtration and washed with water and dried to give compound (6) as a light white solid. (68%, 6.236 g) (Figure 15).

Figure 15: Structure of 4-thiomorpholinoquinazolin-2-amine [Compound 6].

M.p.180-181°C.

ESI-MS m/z 247[M+H]⁺.

¹H NMR (400 MHz, DMSO-d₆) δ ppm 2.67(4H, t, 2 × CH₂ –S), 3.45(4H, t, 2 × CH₂ –N), 6.89(2H, bs) 7.6(¹H,t, Ar-H),7.85(2H,m, Ar- H), 8.15(¹H,d, Ar-H).

¹³C NMR (100 MHz, DMSO-d₆) (δ/ppm): 28(2C, C-S), 53(2C, C-O), 115,123, 128, 130, 132, 153, 160, 180

IR (KBr, ν/cm^–1): 3340 and 3400(N-H Stretching, two bands), 3040 (Ar C-H), 1629 (C=N);

General procedure for synthesis of N-phenyl-4- thiomorpholinoquinazolin-2-amine (8a), 4-thiomorpholino- N-p-tolylquinazolin-2-amine (8b), N-(4-methoxyphenyl)-4- thiomorpholinoquinazolin-2-amine (8c), 4-thiomorpholino- N-(4-(tri fluoro methyl)phenyl)quinazolin-2-amine (8d), N-(4- chlorophenyl)-4-thiomorpholinoquinazolin-2-amine (8e), N-(4-bromophenyl)-4-thiomorpholinoquinazolin-2-amine (8f), N-(4-nitrophenyl)-4-thiomorpholinoquinazolin-2- amine (8g), 4-thiomorpholino-N-(thiophen-2-yl)quinazolin- 2-amine (8i), N-(furan-2-yl)-4-thiomorpholinoquinazolin-2- amine (8j)

A mixture of boronic acid 7(a) (1.5 eq.), 4-thiomorpholinoquinazolin- 2-amine (6) (1 eq.), pyridine (2 m.mol) and 0.5 g Cuo/4A in boiling dichloromethane (10 ml) was stirred under air atmosphere for 20 h. then the mixture was cooled, the solid was filtered, washed with dichloromethane, the filtrate was evaporated. The residue was purified by column chromatography (hexane: Ethyl acetate 4:1 eluent).

N-phenyl-4-thiomorpholinoquinazolin-2-amine (8a): From 4-thio morpholine quinazolin-2-amine (6) (4.065 m.mol, 1 g) and phenyl boronic acid (7a) (6.097 m.mol, 745 mg). The compound was obtained as off-white solid, 60% (785 mg) yield (Figure 16).

m.p. 256-258°C;

Figure 16: Structure of N-phenyl-4-thiomorpholinoquinazolin-2-amine (8a).

IR (KBr) cm-1: 3360 (NH Stretching), 3060 (Ar CH Stretching), 1620 (C=N).

ESI-MS m/z 323[M+H]⁺.

¹H NMR (400 MHz, DMSO-d₆) δ ppm 2.80(4H, t, 2 × CH₂ –S), 3.60(4H, t, 2 × CH₂ –N), 4.7(¹H, bs),6.9(¹H,t), 7.3(2H,m), 7.6(¹H,t, Ar- H),7.7(2H,m),7.85(2H,m, Ar-H), 8.15(¹H,d, Ar-H).

¹³C NMR (100 MHz, DMSO-d₆) (δ/ppm): 28(2C, C-S), 53(2C, C-N), 115,123, 128, 130, 133,140, 153, 175, 180.

4-thiomorpholino-N-p-tolylquinazolin-2-amine (8b): From 4-thiomorpholinoquinazolin-2-amine (6) (4.065 m.mol, 1 g) and 4-methyl phenyl boronic acid (7b) (6.097 m.mol, 830 mg). The compound was obtained as light yellow powder, 62% (846 mg) yield (Figure 17).

Figure 17: Structure of 4-thiomorpholino-N-p-tolylquinazolin-2-amine (8b).

m.p. 247-249°C;

IR (KBr) cm-1: 3360 (NH Stretching), 3070 (CH aryl), 2960 (CH alkyl), 1610 (C=N).

ESI-MS m/z 337[M+H]⁺, 359[M+Na]⁺.

¹H NMR (400 MHz, DMSO-d₆) δ ppm 2.34(3H,S),2.80(4H, t, 2 × CH₂ –S), 3.55(4H, t, 2 × CH₂ –N), 4.4(¹H, bs),6.9(2H,d), 7.3(2H,d), 7.6(¹H,t, Ar-H), 7.80(2H,m, Ar-H), 8.15(¹H,d, Ar-H).

¹³C NMR (100 MHz, DMSO-d₆) (δ/ppm): 28(2C, C-S), 23(Aromatic methyl carbon),53(2C, C-N), 115,123, 126, 130, 133,138, 153, 175, 180.

N-(4-methoxyphenyl)-4-thiomorpholinoquinazolin-2-amine (8c): From 4-thiomorpholinoquinazolin-2-amine (6) (4.065 m.mol, 1 g) and 4-methoxy phenyl boronic acid (7c) (6.097 m.mol, 926 mg). The compound was obtained as off-white solid, 64% (915 mg) yield (Figure 18).

Figure 18: Structure of N-(4-methoxy phenyl)-4-thiomorpholinoquinazolin- 2-amine (8c).

m.p. 238-240°C;

IR (KBr) cm-1: 3340 (NH Stretching), 3090 (CH aryl), 2960 (CH alkyl), 1150(C-O-C), 1600 (C=N), 1590 (C=C);

ESI-MS m/z 353[M+H]⁺, 375[M+Na]⁺

¹H NMR (400 MHz, DMSO-d₆) δ ppm 2.80(4H, t, 2 × CH₂ –S), 3.55(4H, t, 2 × CH₂ –N), 3.9(3H,S,

-OCH₃),4.4(¹H, bs),7(2H,d), 7.6(2H,d), 7.7(¹H,t, Ar-H), 7.80(2H,m, Ar-H), 8.15(¹H,d, Ar-H).

¹³C NMR (100 MHz, DMSO-d₆) (δ/ppm): 29(2C, C-S), 53(2C, C-N), 56(Aromatic methyl carbon), 115,123, 126, 130, 133,138, 153, 175, 180.

4-thiomorpholino-N-(4-(tri fluoro methyl) phenyl) quinazolin- 2-amine (8d): From 4-thiomorpholinoquinazolin-2-amine (6) (4.065 m.mol, 1 g) and 4-Trifluoro methyl phenyl boronic acid (7d) (6.097 m.mol, 1158 mg). The compound was obtained as light yellow solid, 63% (998 mg) yield (Figure 19).

Figure 19: Structure of 4-thiomorpholino-N-(4-(tri fluoro methyl)phenyl) quinazolin-2-amine (8d).

M.p. 221-223°C;

IR (KBr) cm-1: 3350 (NH Stretching), 3010 (CH aryl), 1340(C-F), 1640 (C=N), 1615 (C=C);

ESI-MS m/z 391[M+H]⁺, 413[M+Na]⁺.

¹H NMR (400 MHz, DMSO-d₆) δ ppm 2.80(4H, t, 2 × CH₂ –S), 3.55(4H, t, 2 × CH₂ –N), 4.6(¹H, bs),7.4(2H,d), 7.55(2H,d), 7.7(¹H,t, Ar-H), 7.80(2H,m, Ar-H), 8.15(¹H,d, Ar-H).

¹³C NMR (100 MHz, DMSO-d₆) (δ/ppm): 29(2C, C-S), 53(2C, C-N), 115,124, 126, 130, 133,138, 153, 175, 180.

N-(4-chloro phenyl)-4-thiomorpholinoquinazolin-2-amine (8e): From 4-thiomorpholinoquinazolin-2-amine (6) (4.065 m.mol, 1 g) and 4-chlorophenylboronic acid (7e) (6.097 m.mol, 951 mg). The compound was obtained as light yellow solid, 65% (940 mg) yield (Figure 20).

Figure 20: Structure of N-(4-chloro phenyl)-4-thiomorpholinoquinazolin-2-amine (8e).

m.p. 177-179°C;

IR (KBr) cm-1: 3360 (NH Stretching), 3010 (CH aryl), 1640 (C=N), 1615 (C=C); 746(C-Cl).

ESI-MS m/z 357[M+H]⁺, 359[M+2]⁺

¹H NMR (400 MHz, DMSO-d₆) δ ppm 2.7(4H, t, 2 × CH₂ –S), 3.55(4H, t, 2 × CH₂ –N), 4.9(¹H, bs),7.3(2H,d), 7.75(2H,d), 7.7(¹H,t, Ar-H), 7.80(2H,m, Ar-H), 8.15(¹H,d, Ar-H).

¹³C NMR (100 MHz, DMSO-d₆) (δ/ppm): 30(2C, C-S), 53(2C, C-N), 115,124, 126, 130, 133,138, 153, 175, 180.

N-(4-bromophenyl)-4-thiomorpholinoquinazolin-2-amine (8f): From 4-thiomorpholinoquinazolin-2-amine (6) (4.065 m.mol, 1 g) and 4-bromophenylboronic acid (7f) (6.097 m.mol, 1219 mg). The compound was obtained as off-white solid, 64% (1043 mg) yield (Figure 21).

Figure 21: Structure of N-(4-bromophenyl)-4-thiomorpholinoquinazolin-2-amine (8f).

m.p. 248-250°C;

IR (KBr) cm-1: 3360 (NH Stretching), 3010 (CH aryl), 1640 (C=N), 1615 (C=C); 546(C-Br).

ESI-MS m/z 401[M+H]⁺, 403[M+2]⁺

¹H NMR (400 MHz, DMSO-d₆) δ ppm 2.57(4H, t, 2 × CH₂ –S), 3.45(4H, t, 2 × CH₂ –N), 4.9(¹H, bs),7.1(2H,d), 7.4(2H,d), 7.7(¹H,t, Ar- H), 7.80(2H,m, Ar-H), 8.15(¹H,d, Ar-H).

¹³C NMR (100 MHz, DMSO-d₆) (δ/ppm): 28(2C, C-S), 53(2C, C-N), 115,124, 126, 130, 133,138, 153, 175, 180.

N-(4-nitrophenyl)-4-thiomorpholinoquinazolin-2-amine (8g): From 4-thiomorpholino quinazolin-2-amine (6) (4.065 m.mol, 1 g) and 4-nitrophenylboronic acid (7g) (6.097 m.mol, 1018 mg). The compound was obtained as pale yellow solid, 60% (895 mg) yield (Figure 22).

Figure 22: Structure of N-(4-nitrophenyl)-4-thiomorpholinoquinazolin-2-amine (8g).

m.p. 234-236°C;

IR (KBr) cm-1: 3360 (NH Stretching), 3010 (CH aryl), 1640 (C=N), 1615 (C=C); 1340 and 1560 (N-O Symmetric and Asymmetric stretching in Nitro Group).

ESI-MS m/z 368[M+H]⁺, 390[M+Na]⁺.

¹H NMR (400 MHz, DMSO-d₆) δ ppm 2.57(4H, t, 2 × CH₂ –S), 3.45(4H, t, 2 × CH₂ –N), 4.9(¹H, bs),7.1(2H,d), 7.7(¹H,t, Ar-H), 7.80(2H,m, Ar-H), 8.15(¹H,d, Ar-H),8.2(2H,d).

¹³C NMR (100 MHz, DMSO-d₆) (δ/ppm): 30(2C, C-S), 55(2C, C-N), 115,124, 126, 130, 133,138, 153, 175, 180.

N-(pyridin-4-yl)-4-thiomorpholinoquinazolin-2-amine (8h): From 4-thiomorpholinoquinazolin-2-amine (6) (4.065 m.mol, 1 g) and pyridin-4-ylboronic acid (7h) (6.097 m.mol, 750 mg). The compound was obtained as pale yellow powder, 63% (826 mg) yield (Figure 23).

Figure 23: Structure of N-(pyridin-4-yl)-4-thiomorpholinoquinazolin-2-amine (8h).

m.p. 237-239°C;

IR (KBr) cm-1: 3370 (NH Stretching), 3019 (CH aryl), 1660 (C=N), 1645 (C=C);

ESI-MS m/z 324[M+H]⁺, 346[M+Na]⁺

¹H NMR (400 MHz, DMSO-d₆) δ ppm: 2.67(4H, t, 2 × CH₂ –S), 3.45(4H, t, 2 × CH₂ –N), 4.9(¹H, bs),7.1(2H,d), 7.7(¹H,t, Ar-H), 7.80(2H,m, Ar-H), 8.15(¹H,d, Ar-H),8.5(2H,d).

¹³C NMR (100 MHz, DMSO-d₆) (δ/ppm): 30(2C, C-S), 55(2C, C-N), 110,115,124, 126, 130, 133,138, 153, 175, 180.

4-thiomorpholino-N-(thiophen-2-yl)quinazolin-2-amine (8i): From 4-thio-morpholinoquinazolin-2-amine (6) (4.065 m.mol, 1 g) and thiophen-2-ylboronic acid (7i) (6.097 m.mol, 780 mg). The compound was obtained as light yellow solid, 60% (800 mg) yield (Figure 24).

Figure 24: Structure of 4-thiomorpholino-N-(thiophen-2-yl)quinazolin-2-amine (8i).

m.p. 148-149°C;

IR (KBr) cm-1: 3360 (NH Stretching), 3017 (CH aryl), 1640 (C=N), 1635 (C=C);

ESI-MS m/z 329[M+H]⁺.

¹H NMR (400 MHz, DMSO-d₆) δ ppm : 2.7(4H, t, 2 × CH₂ –S), 3.45(4H, t, 2 × CH₂ –N), 4.9(¹H, bs),6.1(¹H,d),6.94(¹H,d), 6.8(¹H,t), 7.7(¹H,t, Ar-H), 7.80(2H,m, Ar-H), 8.15(¹H,d, Ar-H),8.5(2H,d).

¹³C NMR (100 MHz, DMSO-d₆) (δ/ppm): 30(2C, C-S), 55(2C, C-N), 110,118,124, 126, 130, 133,138, 153, 175, 180.

N-(furan-2-yl)-4-thiomorpholinoquinazolin-2-amine (8j): From 4-thiomorpholinoquinazolin-2-amine (6) (4.065 m.mol, 1 g) and furan-2-ylboronic acid (7j) (6.097 m.mol, 685 mg). The compound was obtained as light yellow solid, 63% (798 mg) yield (Figure 25).

Figure 25: Structure of N-(furan-2-yl)-4-thiomorpholinoquinazolin-2-amine (8j).

m.p. 138-140°C;

IR (KBr) cm-1: 3380 (NH Stretching), 3017 (CH aryl), 1640 (C=N), 1055 (C-O-C);

ESI-MS m/z 313[M+H]⁺.

¹H NMR (400 MHz, DMSO-d₆) δ ppm: 2.7(4H, t, 2 × CH₂ –S), 3.45(4H, t, 2 × CH₂ –N), 4.9(¹H, bs), 6.74(¹H,d), 6.8(¹H,t), 7.7(¹H,t, Ar-H), 7.8(¹H,d), 7.80(2H,m, Ar-H), 8.15(¹H,d, Ar-H),8.5(2H,d).

¹³C NMR (100 MHz, DMSO-d₆) (δ/ppm): 30(2C, C-S), 55(2C, C-N), 110,118,124, 126, 130, 133,138, 153, 175, 180.

Antibacterial studies

The newly prepared compounds were screened for their antibacterial activity against Bacillus subtilis, Staphylococcus aureus, Klebsiella pneumonia and Escherichia coli (clinical isolate) bacterial strains by disc diffusion method. A standard inoculum (1-2 × 10⁷ cfu/ml 0.5 McFarland standards) were introduced on to the surface of sterile agar plates, and a sterile glass spreader was used for even distribution of the inoculums. The disks measuring 6 mm in diameters were prepared from Whatman no. 1 filter paper and sterilized by dry heat at 140°C for 1 h. The sterile disks previously soaked in a known concentration of the test compounds were placed in nutrient agar medium. Solvent and growth controls were kept. Amoxicillin (30 μg) was used as positive control and the disk poured in DMSO was used as negative control and the test compounds were dissolved in DMSO at concentration of 100 and 50 μg/mL. The plates were inverted and incubated for 24 h at 37°C. The susceptibility was assessed on the basis of diameter of zone of inhibition against Gram-positive and Gram-negative strains of bacteria. Inhibition of zone of measured and compared with controls. The bacterial zone of inhibition values are given in Table 1. The order of activity was 8i>8d>8h>8g>8j >8e >8f>8a>8b>8c (Table 1).

Table 1: Anti-bacterial activity of Novel Quinazoline Derivatives 8(a-j).

Antifungal studies

The newly prepared compounds were screened for their antifungal activity against Candida albicans and Aspergillus flavus in DMSO by agar diffusion method. Sabourauds agar media was prepared by dissolving peptone (1 g), D-glucose (4 g) and agar (2 g) in distilled water (100 ml) and adjusting pH 5.7. Normal saline was used to make suspension of corresponding species. Twenty millilitres of agar media was poured into each Petri dish. Excess of suspension was decanted and the plates were dried by placing in an incubator at 37°C for 1 h using an agar punch, wells were made and each well was labelled. A control was also prepared in triplicate and maintained at 37°C for 3-4 days. The fungal activity of each compound was compared with Fluconazole as a standard drug. Inhibition zone were measured and compared with the controls. The fungal zone of inhibition values are given in Table 2.

Table 2: Anti-fungal activity of Novel Quinazoline Derivatives 8a-j.

Chemistry

The reaction sequences Employed for synthesis of title compounds are shown. In the present work, the starting quinazoline-2,4-diol (2) was prepared from 2-aminobenzoic acid (1) and Urea according to synthetic procedure was prepared according to synthetic procedure [37]. 2,4-dichloroquinazoline (3) was prepared according to synthetic procedure [38]. The 4-(2-chloroquinazolin-4-yl)thiomorpholine (5) was prepared from thio-morpholine(4) and Compound (3) according to synthetic procedure [39], which on further treatment with aqueous ammonia to get 4-thiomorpholinoquinazolin-2- amine (6) according to synthetic procedure [40], which were treated with different substituted phenyl boronic acids and Heterocyclic boronic acids under Chan-lam coupling reaction conditions to get Target Novel Quinazoline derivatives (8a-j) according to synthetic procedure [41]. All compounds displayed IR, ¹H and ¹³C NMR and mass spectra consistent with the assigned structures. ¹H NMR and IR spectrum of compounds (8 a-j) showed singlet at 2.3 ppm, 3.8 ppm are due to the aromatic methyl group protons and Aromatic methoxy group protons. The most characteristic IR absorption bands are at 1140 cm-1 (C-O-C), 740 cm-1 (C-Cl) and 1324 and 1552 cm-1 (N-O Stretching in Nitro group). The mass spectra of all the final derivatives showed comparable molecular ion peak with respect to molecular formula.

Anti-microbial studies

The newly synthesized compounds (8a-j) were screened for their in vitro anti-bacterial activity against Bacillus subtilis, Staphylocouccus aureus, Klebsiella pneumonia and Escherichia coli using Amoxicillin as standard by disc diffusion method (zone of inhibition) [42,43]. The test compounds were dissolved in di methyl sulfoxide (DMSO) at concentrations of 50 and 100 μg/mL. The antibacterial screening revealed that all the tested compounds showed good inhibition against various tested microbial strains compared to the standard drug. Along with the synthesized compounds 8i, 8d, 8h, 8g were found to be more active against tested bacterial strains as compared to the standard. The in vitro antifungal activities for compounds 8a-8j were determined by agar diffusion method [43]. The results indicate that, among the tested compounds 8i, 8d, 8h, 8g were active against all tested fungal strains. The enhanced activities are due to electron withdrawing groups viz., -CF3 and Thiophene ring attached to Quinazoline core ring. All other compounds such as phenyl ring with methyl and methoxy groups in Quinazoline core structure showed lesser antifungal activity as compared with standard Fluconazole. The Tables 1 and 2 depict the antimicrobial screening results of the final compounds.

The research study reports the successful synthesis and antimicrobial activity of novel Quinazoline as a core unit containing different Substituted Phenyl / Heterocyclic derivatives. The antimicrobial activity study revealed that all the tested compounds showed good antibacterial and antifungal activities against pathogenic strains. The structure and biological activity relationship of title compounds indicate that the presence of electron withdrawing groups like –CF₃ and Thiophene ring attached to the Quinazoline ring were responsible for good antimicrobial activity and hence compounds 8i, 8d, 8h and 8g exhibited more potent anti-microbial activity of all tested pathogenic strains.

Authors are thankful to our Research Supervisor Prof. K. Sudhakar Babu (KSB) Sir and L. K. Ravindranath Sir for providing us required facilities and motivation for completion of the Research work. We also extend our gratitude towards Laxai Avanti Life Sciences Pvt Ltd., Hyderabad for providing us facilities of IR Spectra, ¹H NMR for characterization of Novel Synthesized compounds.