Scholarly article on topic 'A simple procedure for synthesis of 3H-quinazolin-4-one hydrazones under mild conditions'

A simple procedure for synthesis of 3H-quinazolin-4-one hydrazones under mild conditions Academic research paper on "Chemical sciences"

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{Hydrazones / Condensation / 2-Hydrazino-3-phenyl-3H-quinazolin-4-ones / Acetylation}

Abstract of research paper on Chemical sciences, author of scientific article — Mohamed F. Abdel-Megeed, Mohamed M. Azaam, Gamal A. El-Hiti

Abstract Condensation of 6-bromo- and 6,8-dibromo-2-hydrazino-3-phenyl-3H-quinazolin-4-ones with d-sugars in the presence of a catalytic quantity of glacial acetic acid gave the corresponding hydrazones in good yields. Acetylation of hydrazones with acetic anhydride in anhydrous pyridine gave the corresponding acetyl hydrazones in high yields. Also, other hydrazones were synthesized from condensation of 2-hydrazino-3H-quinazolin-4-ones with aromatic aldehydes in the presence of a catalytic quantity of piperidine.

Academic research paper on topic "A simple procedure for synthesis of 3H-quinazolin-4-one hydrazones under mild conditions"

Journal of Saudi Chemical Society (2011) xxx, xxx-xxx

King Saud University Journal of Saudi Chemical Society

www.ksu.edu.sa www.sciencedirect.com

ORIGINAL ARTICLE

A simple procedure for synthesis of 3H-qmnazolin-4-one hydrazones under mild conditions

Mohamed F. Abdel-Megeed a, Mohamed M. Azaam a, Gamal A. El-Hiti a b *

a Chemistry Department, Faculty of Science, Tanta University, Tanta 31527, Egypt b School of Chemistry, Cardiff University, Main Building, Park Place, Cardiff CF10 3AT, UK

Received 10 October 2011; accepted 6 December 2011

KEYWORDS

Hydrazones;

Condensation;

2-Hydrazino-3-phenyl-3H-

quinazolin-4-ones;

Acetylation

Abstract Condensation of 6-bromo- and 6,8-dibromo-2-hydrazino-3-phenyl-3H-quinazolm-4-ones with D-sugars in the presence of a catalytic quantity of glacial acetic acid gave the corresponding hydrazones in good yields. Acetylation of hydrazones with acetic anhydride in anhydrous pyridine gave the corresponding acetyl hydrazones in high yields. Also, other hydrazones were synthesized from condensation of 2-hydrazino-3H-quinazolin-4-ones with aromatic aldehydes in the presence of a catalytic quantity of piperidine.

© 2011 King Saud University. Production and hosting by Elsevier B.V. All rights reserved.

1. Introduction

Quinazoline derivatives exhibit a wide variety of pharmacological activities (Honda et al., 1979; Alafeefy, 2008; Al-Deeb and Alafeefy, 2008; Kadi, 2011). Therefore, methods for the synthesis and/or modification of this ring system are always of interest. They are important intermediates in the synthesis of

* Corresponding author at: School of Chemistry, Cardiff University, Main Building, Park Place, Cardiff CF10 3AT, UK. Tel.: +44 7902394871.

E-mail addresses: el-hitiga@cardiff.ac.uk, gelhiti@yahoo.co.uk (G.A. El-Hiti).

1319-6103 © 2011 King Saud University. Production and hosting by Elsevier B.V. All rights reserved.

Peer review under responsibility of King Saud University. doi:10.1016/j.jscs.2011.12.009

a variety of valuable heterocyclic compounds (Shaban et al., 1991; El-Hiti, 2000; El-Hiti et al., 2011).

In view of the biological activities of both quinazolines and sugar moieties, we have reported convenient procedures for the synthesis of various quinazoline glycosides (Abdo et al., 1995; Abdel-Megeed et al., 1995, 2000; El-Brollosy et al., 2003) and hydrazones, Abdel-Megeed et al., 1999; El-Hiti et al., 2000; Saleh et al., 2003) as a continuation of our own interest in the synthesis and/or modification of quinazoline derivatives (Smith et al., 1995, 1996, 2003, 2004, 2005a,b; El-Hiti, 1997, 2003, 2004; El-Hiti and Abdel-Megeed, 2005; Abdel-Megeed et al., 2007).

In this work we now report the successful synthesis of a series of hydrazones containing 3H-quinazolin-4-one ring system under mild conditions.

2. Experimental

Melting points (0C, uncorrected) were determined on an electrothermal melting MEL-TEMP II apparatus. 1H and 13C NMR spectra were recorded in DMSO-d6 using a Bruker AC400 spectrometer operating at 400 MHz for 1H and

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100 MHz for 13C. Chemical shifts d are reported in parts per million (ppm) relative to tetramethylsilane (TMS) and coupling constants J are in Hz. Assignments of signals are based on integration values, coupling patterns and expected chemical shift values and have not been rigorously confirmed. Signals with similar characteristics might be interchanged. IR Spectra were recorded on a Perkin-Elmer 1430 spectrometer using KBr disc technique. All samples were examined by thin layer chromatography (TLC), which was performed on EM silica gel F254 sheet (0.2 mm) with chloroform/acetone (5:2; v/v), hex-ane/acetone (5:2; v/v) or petroleum ether (40-60 0C)/acetone (5:2; v/v) as developing eluents. The spots were detected with UV Lamp Model UV GL-58.

2.1. Synthesis of 6-bromo-2-hydrazino-3-phenyl-3H-quinazolin-4-one (3) and 6,8-dibromo-2-hydrazino-3-phenyl-3H-quinazolin-4-one (4)

A mixture of 1 or 2 (10.0 mmol) and hydrazine hydrate (11.0 mmol) in EtOH (100 mL) was heated under reflux for 48 h. The solid obtained on cooling was collected by filtration, washed with EtOH and recrystallized from BuOH to give pure product.

Compound 3: Yield 72%, m.p. 260-262 0C; IR (KBr, cm"1) 3256, 3599, 1660, 580; NMR (DMSO-d6) d: 8.21-7.13 (m, 8H, aromatics), 5.81 (s, 2H, NH2, D2O exchange), 5.40 (s, 1H, NH, D2O exchange); 13C NMR (DMSO-d6) d: 160.9 (C-4), 153.2 (C-2), 138.7 (C-8a), 137.5 (C-7), 134.5 (C-1 of Ph), 130.3 (C-4 of Ph), 129.3 (C-3/C-5 of Ph), 128.9 (C-2/C-6 of Ph), 128.9 (C-5), 123.6 (C-6), 119.4 (C-4a), 114.6 (C-8).

Compound 4: Yield 67%, m.p. 240 0C; IR (KBr, cm"1) 3282, 3575, 1674, 585; NMR (DMSO-d6) d: 8.17-7.11 (m, 7H, aromatics), 5.79 (s, 2H, NH2, D2O exchange), 5.43 (s, 1H, NH, D2O exchange).

2.2. Synthesis ofD-sugar-1-(6-bromo-3-phenyl-4-oxoquinazolin-2-yl)hydrazones (6) and D-sugar-1-(6,8-dibromo-3-phenyl-4-oxoquinazolin-2-yl)hydrazones (7)

A mixture of 3 or 4 (10.0 mmol), appropriate D-sugar 5 (11.0 mmol) and AcOH (0.2 mL) in EtOH (20 mL) was heated under reflux for 4 h. The yellowish white solid that separated on cooling was filtered, washed with H2O (2 x 20 mL) then EtOH (2 x 20 mL) to give pure products 6 or 7.

Compound 6a: Yield 71%, m.p. 215-216 0C; IR (KBr, cm"1) 3320, 2925, 1675, 1582, 583; NMR (DMSO-d6) d: 9.22 (s, 1H, NH, D2O exchange), 8.01-6.83 (m, 8H, aromatics), 5.53 (d, J = 4.7 Hz, 1H, H-1 of glucose), 4.71-3.39 (m, 11H, other glucose protons).

Compound 6b: Yield 69%, m.p. 194-195 0C; IR (KBr, cm"1) 3323, 2923, 1674, 1611, 583; 1H NMR (DMSO-d6) d: 9.50 (s, 1H, NH, D2O exchange), 8.01-7.09 (m, 8H, aromatics), 5.68 (d, J = 4.9 Hz, 1H, H-1 of galactose), 4.51-3.50 (m, 11H, other galactose protons).

Compound 6c: Yield 68%, m.p. 220-222 0C; IR (KBr, cm"1) 3324, 2923, 1676, 1581, 582; 1H NMR (DMSO-d6) d: 9.31 (s, 1H, NH, D2O exchange), 7.88-6.89 (m, 8H, aromatics), 5.50 (d, J = 5.0 Hz, 1H, H-1 of mannose), 4.72-3.43 (m, 11H, other mannose protons).

Compound 6d: Yield 68%, m.p. 240-241 0C; IR (KBr, cm"1) 3325, 2923, 1667, 1602, 583; 1H NMR (DMSO-d6) d: 9.49 (s, 1H, NH, D2O exchange), 8.11-7.04 (m, 8H, aromat-

ics), 5.72 (d, J = 5.1 Hz, 1H, H-1 of xylose), 4.81-3.69 (m, 9H, other xylose protons).

Compound 6e: Yield 69%, m.p. 180-181 0C; IR (KBr, cm"1) 3325, 2932, 1673, 1610, 585; 1H NMR (DMSO-d6) d: 9.43 (s, 1H, NH, D2O exchange), 7.94-7.03 (m, 8H, aromatics), 5.82 (d, J = 5.1 Hz, 1H, H-1 arabinose), 4.93-3.64 (m, 9H, other arabinose protons).

Compound 7a: Yield 70%, m.p. 276-277 0C; IR (KBr, cm"1) 3323, 3063, 1685, 1583, 585; 1H NMR (DMSO-d6) d: 9.21 (s, 1H, NH, D2O exchange), 7.99-6.91 (m, 7H, aromatics), 5.52 (d, J = 4.8 Hz, 1H, H-1 of glucose), 4.82-3.71 (m, 11H, other glucose protons).

Compound 7b: Yield 68%, m.p. 230-231 0C; IR (KBr, cm"1) 3327, 2926, 1677, 1588, 584; 1H NMR (DMSO-d6) d: 9.36 (s, 1H, NH, D2O exchange), 8.01-6.92 (m, 7H, aromatics), 5.59 (d, J = 4.7 Hz, 1H, H-1 of galactose), 5.44-3.53 (m, 11H, other galactose protons).

Compound 7c: Yield 61%, m.p. 244-245 0C; IR (KBr, cm"1) 3328, 2927, 1672, 1590, 583; 1H NMR (DMSO-d6) d: 9.40 (s, 1H, NH, D2O exchange), 8.01-6.74 (m, 7H, aromatics), 5.53 (d, J = 5.1 Hz, 1H, H-1 of mannose), 5.40-3.83 (m, 11H, other mannose protons); 13C NMR (DMSO-d6) d: 160.3 (C-4), 159.2 (C-1 of mannose), 147.2 (C-2), 138.7 (C-8a), 138.0 (C-7), 136.5 (C-1 of Ph), 129.4 (C-4 of Ph), 128.9 (C-3/C-5 of Ph), 128.4 (C-2/C-6 of Ph), 128.3 (C-5), 123.6 (C-8), 119.4 (C-4a), 116.3 (C-6), 73.4 (C-2 of mannose), 72.2 (C-3 of mannose), 70.5 (C-4 of mannose), 69.0 (C-5 of mannose), 64.0 (C-6 of mannose).

Compound 7d: Yield 57%, m.p. 194-195 0C; IR (KBr, cm"1) 3326, 2924, 1678, 1588, 584; 1H NMR (DMSO-d6) d: 9.57 (s, 1H, NH, D2O exchange), 8.11-7.03 (m, 7H, aromatics), 5.72 (d, J = 5.2 Hz, 1H, H-1 xylose), 5.31-3.79 (m, 9H, other xylose protons).

Compound 7e: Yield 68%, m.p. 265-266 0C; IR (KBr, cm"1) 3324, 2926, 1675, 1591, 586; 1H NMR (DMSO-d6) d: 9.42 (s, 1H, NH, D2O exchange), 8.14-6.93 (m, 7H, aromatics), 5.63 (d, J = 5.0 Hz, 1H, H-1 of arabinose), 5.22-3.63 (m, 9H, other arabinose protons).

2.3. Synthesis of per-O-acetyl-D-sugar-1-acetyl-1-(6-bromo-3-phenyl-4-oxoquinazolin-2-yl)hydrazones (8) and per-O-acetyl-D-sugar-1-(6,8-dibromo-3-phenyl-4-oxoquinazolin-2-yl)hydrazones (9)

A cold (0 0C) solution of 6 or 7 (1.0 g) in anhydrous pyridine (5 mL) was treated with freshly distilled Ac2O (5 mL). The reaction mixture was stirred overnight at room temperature then poured onto iced H2O (100 mL). The solid obtained was filtered, washed repeatedly with H2O (4 x 20 mL) and recrystallized from EtOH to give pure products 8 or 9.

Compound 8a: Yield 68%, m.p. 160-161 0C; IR (KBr, cm"1) 2927, 1748, 1700, 1611, 585; 1H NMR (DMSO-d6) d: 8.13-6.53 (m, 8H, aromatics), 5.61 (d, J = 4.6 Hz, 1H, H-1 of glucose), 5.33-3.81 (m, 6H, other glucose protons), 2.220.84 (6s, 18H, 6CH3CO).

Compound 8b: Yield 68%, m.p. 100-101 0C; IR (KBr, cm"1) 2924, 1747, 1697, 1612, 614; 1H NMR (DMSO-d6) d:

8.10-6.54 (m, 8H, aromatics), 5.52 (d, J = 4.8 Hz, 1H, H-1 of galactose), 5.44-3.42 (m, 6H, other galactose protons),

2.11-0.82 (6s, 18H, 6CH3CO).

Compound 8c: Yield 65%, m.p. 180-181 0C; IR (KBr, cm"1) 2924, 1739, 1676, 1600, 582; 1H NMR (DMSO-d6) d:

8.09-6.84 (m, 8H, aromatics), 5.53 (d, J = 4.9 Hz, 1H, H-1 of mannose), 5.22-3.51 (m, 6H, other mannose protons), 2.111.02 (6s, 18H, 6CH3CO).

Compound 8d: Yield 62%, m.p. 150-151 0C; IR (KBr, cm"1) 2925, 1743, 1696, 1602, 595; 1H NMR (DMSO-d6) d: 8.08-6.63 (m, 8H, aromatics), 5.57 (d, J = 5.0 Hz, 1H, H-1 of xylose), 5.42-3.64 (m, 5H, other xylose protons), 2.190.91 (5s, 15H, 5CH3CO).

Compound 8e: Yield 66%, m.p. 90-91 0C; IR (KBr, cm"1) 2935, 1747, 1699, 1604, 601; 1H NMR (DMSO-d6) d: 8.02-6.91 (m, 8H, aromatics), 5.90 (d, J = 5.1 Hz, 1H, H-1 of arabinose), 5.41-3.73 (m, 5H, other arabinose protons), 2.21-1.00 (5s, 15H, 5CH3CO).

Compound 9a: Yield 73%, m.p. 260-261 0C; IR (KBr, cm"1) 3324, 2925, 1747, 1705, 1592, 581; 1H NMR (DMSO-d6) d: 9.22 (s, 1H, NH, D2O exchange), 8.03-6.94 (m, 7H, aromatics), 5.52 (d, J = 4.8 Hz, 1H, H-1 of glucose), 5.11-3.64 (m, 6H, other glucose protons), 2.22-0.74 (5 s, 15H, 5CH3CO).

Compound 9b: Yield 65%, m.p. 200-201 0C; IR (KBr, cm"1) 3325, 2924, 1748, 1707, 1591, 583; 1H NMR (DMSO-d6) d: 9.38 (s, 1H, NH, D2O exchange), 8.12-6.94 (m, 7H, aromatics), 5.54 (d, J = 4.9 Hz, 1H, H-1 of galactose), 5.24-3.63 (m, 6H, other galactose protons), 2.21-0.64 (5s, 15H, 5CH3CO).

Compound 9c: Yield 63%, m.p. 220-221 0C; IR (KBr, cm"1) 3326, 2926, 1743, 1697, 1601, 584; 1H NMR (DMSO-d6) d: 9.32 (s, 1H, NH, D2O exchange), 8.11-6.94 (m, 7H, aromatics), 5.54 (d, J = 4.6 Hz, 1H, H-1 of mannose), 5.23-3.54 (m, 6H, other mannose protons), 2.20-0.74 (5s, 15H, 5CH3CO).

Compound 9d: Yield 53%, m.p. 180-181 0C; IR (KBr, cm"1) 3323, 2926, 1748, 1707, 1591, 605; 1H NMR (DMSO-d6) d: 9.41 (s, 1H, NH, D2O exchange), 8.12-6.94 (m, 7H, aromatics), 5.54 (d, J = 4.9 Hz, 1H, H-1 of xylose), 5.65-3.55 (m, 5H, other xylose protons), 2.14-0.64 (4s, 12H, 4CH3CO).

Compound 9e: Yield 59%, m.p. 250-251 0C; IR (KBr, cm"1) 3324, 2930, 1742, 1699, 1590, 588; 1H NMR (DMSO-d6) d: 9.45 (s, 1H, NH, D2O exchange), 8.05-6.94 (m, 7H, aromatics), 5.55 (d, J = 5.1 Hz, 1H, H-1 of arabinose), 5.35-3.74 (m, 5H, other arabinose protons), 2.20-0.65 (4s, 12H, 4CH3CO).

2.4. Synthesis of aldehyde-1-(6-bromo-3-phenyl-4-oxoquinazolin-2-yl)hydrazones (11) and aldehyde-1-(6,8-dibromo-3-phenyl-4-oxoquinazolin-2-yl)hydrazones (12)

A mixture of 3 or 4 (10.0 mmol), appropriate aromatic aldehyde 10 (11.0 mmol) and piperidine (1.0 mL) in dry EtOH (30 mL) was heated under reflux for 5 h. The solid obtained on cooling was filtered, washed with EtOH (2 x 20 mL) and recrystallized from EtOH to give pure products 11 or 12. The physical properties of 11 and 12 are recorded in Table 1.

Compound 11a: Yield 70%, m.p. 300-301 0C; IR (KBr, cm"1) 3426, 1665, 1558, 619; 1H NMR (DMSO-d6) d: 9.23 (s, 1H, NH, D2O exchange), 7.81-6.56 (m, 13H, aromatics), 5.55 (s, 1H, CH).

Compound 11b: Yield 66%, m.p. 256-266 0C; IR (KBr, cm"1) 3321, 1674, 1571, 649; 1H NMR (DMSO-d6) d: 9.22 (s, 1H, NH, D2O exchange), 8.11 (s, 1H, OH, D2O exchange), 7.92-6.95 (m, 12H, aromatics), 6.72 (s, 1H, CH).

Compound 11c: Yield 67%, m.p. 223-224 0C; IR (KBr, cm"1) 3460, 1679, 1595, 581; 1H NMR (DMSO-d6) d: 8.44

Table 1 Synthesis of hydrazones of 11 and 12 according to

Scheme 3.

Product X Ar m.p. (°C) Yield (%)

11a H C6H5 300-301 70

11b H -HOC6H4 265-266 66

11c H -MeOC6H4 223-224 67

11d H -ClC6H4 250-251 63

11e H -NO2C6H4 280-281 73

11f H -Me2NC6H4 210-211 59

12a Br C6H5 190-191 65

12b Br -HOC6H4 280-281 59

12c Br -MeOC6H4 235-236 61

12d Br -ClC6H4 285-286 58

12e Br -NO2C6H4 240-241 68

12f Br -Me2NC6H4 250-251 55

Yield for pure product after crystallization from ethanol.

(s, 1H, NH, D2O exchange), 8.13-6.94 (m, 12H, aromatics), 5.73 (s, 1H, CH), 3.82 (s, 3H, OMe).

Compound 11d: Yield 63%, m.p. 250-251 0C; IR (KBr, cm"1) 3321, 1683, 1593, 513; 1H NMR (DMSO-d6) d: 9.24 (s, 1H, NH, D2O exchange), 8.12-6.95 (m, 12H, aromatics),

5.57 (s, 1H, CH).

Compound 11e: Yield 73%, m.p. 250-251 0C; IR (KBr, cm"1) 3346, 1680, 1616, 582; 1H NMR (DMSO-d6) d: 9.23 (s, 1H, NH, D2O exchange), 8.20-6.96 (m, 12H, aromatics),

5.58 (s, 1H, CH).

Compound 11f: Yield 59%, m.p. 210-211 0C; IR (KBr, cm"1) 3323, 1678, 1593, 616; 1H NMR (DMSO-d6) d: 8.66 (s, 1H, NH, D2O exchange), 8.03-6.84 (m, 12H, aromatics),

5.54 (s, 1H, CH), 2.8 (s, 6H, NMe2).

Compound 12a: Yield 65%, m.p. 190-191 0C; IR (KBr, cm"1) 3426, 1667, 1615, 614; 1H NMR (DMSO-d6) d: 9.25 (s, 1H, NH, D2O exchange), 8.41-7.25 (m, 12H, aromatics), 6.75 (s, 1H, CH).

Compound 12b: Yield 59%, m.p. 280-281 0C; IR (KBr, cm"1) 3438, 1695, 1604, 541; 1H NMR (DMSO-d6) d: 9.60 (s, 1H, NH, D2O exchange), 8.22 (s, 1H, OH, D2O exchange), 7.91-6.84 (m, 11H, aromatics), 5.84 (s, 1H, CH).

Compound 12c: Yield 61%, m.p. 235-236 0C; IR (KBr, cm"1) 3438, 1675, 1612, 582; 1H NMR (DMSO-d6) d: 9.60 (s, 1H, NH, D2O exchange), 8.22-7.15 (m, 11H, aromatics), 5.71 (s, 1H, CH), 3.80 (s, 3H, OMe).

Compound 12d: Yield 58%, m.p. 285-286 0C; IR (KBr, cm"1) 3421, 1777, 1614, 584; 1H NMR (DMSO-d6) d: 9.52 (s, 1H, NH, D2O exchange), 8.32-7.05 (m, 11H, aromatics), 5.82 (s, 1H, CH).

Compound 12e: Yield 68%, m.p. 240-241 0C; IR (KBr, cm"1) 3328, 1678, 1614, 583; 1H NMR (DMSO-d6) d: 9.34 (s, 1H, NH, D2O exchange), 8.34-6.96 (m, 11H, aromatics),

5.55 (s, 1H, CH).

Compound 12f: Yield 55%, m.p. 250-252 0C; IR (KBr, cm"1) 3426, 1674, 1604, 580; 1H NMR (DMSO-d6) d: 9.62 (s, 1H, NH, D2O exchange), 8.26-6.94 (m, 11H, aromatics), 5.82 (s, 1H, CH), 3.01 (s, 6H, NMe2).

3. Results and discussion

6-Bromo-2-hydrazino-3-phenyl-3H-quinazolin-4-one (3) and 6,8-dibromo-2-hydrazino-3-phenyl-3H-quinazolin-4-one (4)

1 X= H

2 X= Br

NH2NH2, EtOH reflux

3 X= H (72%)

4 X = Br (67%%

Scheme 1 Synthesis of 2-hydrazino-3-phenyl-3H-quinazolin-4-ones 3 and 4.

3 X= H

4 X= Br

—OH —OH CH2OH a

— OAc

AcO—

EtOH AcO H

6a-e X = H 7a-e X = Br

Ac2O pyridine

HOHO—

HOHO—

—OH CH2OH b

—OH —OH CH2OH

—OH CH2OH d

—OAc

AcO—

— OAc AcO—

— OAc CH2OAc

AcO— AcO—

—OAc CH2OAc

OAc AcO—

—OAc

—OAc

CH2OAc c

AcO—

—OH —OH CH2OH e

—OAc CH2OAc

—OAc

—OAc

CH2OAc e

Scheme 2 Synthesis of hydrazones 6 and 7 and their acetyl derivatives 8 and 9.

were synthesized in 72% and 67% yields, respectively, from reactions of 6-bromo-3-phenyl-2-thioxo-3H-quinazolin-4-one

(1) and 6,8-dibromo-3-phenyl-2-thioxo-3H-quinazolin-4-one

(2) with hydrazine hydrate in boiling ethanol (Scheme 1). Condensation of 3 and 4 with equimolar amounts of monosaccharides 5a-e (D-glucose, D-galactose, D-mannose, D-xylose and D-arabinose) in ethanol and in the presence of a catalytic amount of glacial acetic acid under reflux conditions for 4 h afforded the corresponding hydrazones 6a-e and 7a-e, respectively (Scheme 2) in 57-71% yields.

The IR spectra of 6 and 7 showed absorption bands at 3320-3428 cm"1 region due to the stretching vibration of

NH groups and hydroxyl groups of the sugar residue. The bands at 1667-1685 cm"1 and 582-586 cm"1 region are due to C=O and C-Br bonds, respectively. The 1H NMR spectra of 6 and 7 are characterized by the presence of CH=N protons as doublets and resonated within the 5.50-5.82 ppm region. The NH protons resonated as exchangeable singlet signals at 9.21-9.57 ppm region.

Acetylation of hydrazones 6a-e with freshly distilled acetic anhydride in anhydrous pyridine at room temperature gave the corresponding acetylated hydrazones 8a-e (Scheme 2) in 6268% yields. The spectroscopic data of 8 indicated that peracet-ylation had taken place at both the polyol residue and NH

N NHNH2 X

3 X = H

4 X = Br

Ar piperidine

11a-f X = H 12a-f X = Br

Scheme З Synthesis of hydrazones ll and l2.

groups. However, acetylation 7a-e under similar conditions gave the corresponding acetylated hydrazones 9a-e (Scheme 2) in 53-73% yields in which peracetylation had taken place only at the polyol residue without affecting the NH groups.

The IR spectra of 8 and 9 showed strong absorption bands at 1739-1748 cm"1 due to the stretching vibrations of ester (O-C=O) carbonyl groups. The IR spectra of 8 showed the absence of absorption bands due to NH groups. While, IR spectra of 9 showed absorption bands at 3323-3326 cm"1 due to the stretching vibration of NH groups. The 1H NMR spectra of 8 showed the absence of any exchangeable signals due to the NH protons. While, 1H NMR spectra of 9 showed the presence of exchangeable singlet signals that resonated at 9.22-9.45 ppm region due to the NH protons.

Our attention was next turned to attempt reactions of 3 and 4 with aromatic aldehydes. It was found that reactions of 3 and 4 with aromatic aldehydes 10a-f, such as benzaldehyde, 4-hydroxybenzaldehyde, 4-anisaldehyde, 4-chlorobenz-aldehyde, 4-nitrobenzaldehyde and 4-(N,N-dimethylamino)benzalde-hyde, in dry ethanol and in the presence of few drops of piper-idine as a catalyst gave the corresponding hydrazones 11a-f and 12a-f, respectively (Scheme 3) in good yields. The physical data of 11 and 12 are recorded in Table 1.

The IR spectra of 11 and 12 showed strong absorption bands that appeared at 1674-1677 cm"1 region due to the stretching vibrations of the quinazolinone carbonyl group. They also showed absorption bands within the 33213460 cm"1 region due to the stretching vibrations of the NH groups and absorption bands at 513-649 cm"1 region are due to C-Br bonds. 1H NMR spectra of 11 and 12 showed the presence of CH=N protons that resonated at 5.57-6.75 ppm region, while the NH protons resonated as exchangeable singlet signals at 8.44-9.62 ppm region.

Acknowledgement

The author expresses his sincere thanks and gratitude to Professor Keith Smith, School of Chemistry, Cardiff University, UK for recording the NMR spectra.

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