Synthesis, Characterization and CNS Depressant Activity of Some New Mannich Bases Derivatives
Shivaji Bhattacharjee, J. Saravanan, S. Mohan, Monica Arora
Department of Pharmaceutical Chemistry, PES College of Pharmacy, Bangalore-50, Karnataka, India.
*Corresponding Author E-mail: bhattacharjee.shivaji@gmail.com
ABSTRACT:
The novel 2-amino-3-carbethoxy-4- phenyl thiophene was synthesized by using a acetophenone and ethyl cyano acetate and the parent compound was reacted with chloroacetic acid and glacial acetic acid, the chloro compound was then substituted with different substituted primary and secondary amines to obtain a series of title compounds [SBJa 1-8]. All the new title compounds were characterized by spectral data and were screened for CNS depressant activity.
In conclusion, it can be inferred that the electron donating groups on the phenyl ring at R of the title compounds influenced the CNS depressant activity.
KEYWORDS: Synthesis, Thiophene, Manich Base, Characterization, CNS Depressant activity
In medicinal chemistry thiophene derivatives have been very well known for their therapeutic applications. The benzo[b]thiophene system often present in biologically active compounds and many examples of biological activities found for small nucleus based on the benzo[b]thiophene moiety can be referred. The literature indicated that compounds having benzo[b]thiophene nucleus possess broad range of biological activities namely anti-inflammatory1,antifungal2, analgesic3, antiallergic 4,ocular hypotensive 5, antitumor 6, alkaline phosphatise inhibitor7 and antimicrobial8 activities.
MATERIALS AND METHOD:
Chemicals
Ethyl cyanoacetate, acetophenone, sulphur, 4’-di methyl amino benzaldehyde,piperazine, morpholine, o-toludine, p-toludine, m-toludine, 2 fluoro aniline, 4 fluoro aniline, 3 chloro 4 fluoro aniline were obtained from local dealer.
Analytical TLC was performed on Silica plates- GF254 (Merck) with visualization by UV or iodine vapors. Melting points were determined in open capillaries on a Thermonic Melting point apparatus and are uncorrected. The IR spectra (KBr, λ Max, cm-1) were run on Perkin Elmer FTIR Spectrophotometer. 1H-NMR (in CDCl3 / DMSO-d6) spectra were recorded using AMX-400 with TMS as internal standard. MS spectra were recorded on Brucker DPX 200. Elemental analyses were performed on Carlo Erba 1108 elemental analyzer and were within ± 0.4% of theoretical values. All the chemicals used were of analytical grade.
Preparation of 2-amino-3-carbethoxy-4-phenyl thiophene (SBJ)
A mixture of ethyl cyanoacetate (4.26ml; 0.04 M), acetophenone (4.5ml; 0.04 M), ammonium acetate (2 g) and glacial acetic acid (2 ml) in benzene (100 ml) was refluxed with an arrangement for continuous separation of water using dean stark apparatus. After 12 hours the reaction mixture was cooled, diluted with 10 ml benzene and washed with sodium carbonate solution (10% w/v in water) and water successively thrice and dried over anhydrous sodium sulphate. The solvent was removed under vacuum and the intermediate crude product obtained was immediately processed for next step.To a mixture of the crude product in alcohol (10 ml) was added Sulphur (1.28 g; 0.04 M) in portions followed by the addition of, Diethylamine (4.0 ml) drop wise with stirring. The reaction mixture was stirred for 3 hours at 40-45 ºC and chilled over night in refrigerator. The solid obtained was filtered, washed with ethanol and crystallized from benzene.1H NMR: 7.5-6 (5 Aromatic H); 6.3 (1H, thiophene ring); 4.29(2H of CH2); 4 (2H of NH2); 1.3(3H of CH3).
Preparation of 2-(2chloroacetamido)-4-phenylthiophene -3ethylcarboxylate (SBJa)
A mixture of SBJ (2g; 0.02M), chloro acetyl chloride (1eq) and glacial acetic acid (10 ml) was refluxed for 7 hours and cooled to room temperature. This reaction mixture was then poured in crushed ice with continuous stirring. The precipitate obtained was filtered, dried and recrystalized from ethanol water mixture (1:1).
Preparation of Mannich Bases
A mixture of the starting compound 5SBJa and required primary and secondary aromatic amines (0.0025mol) in benzene (10 mi) and catalytic amount of pyridine was refluxed for 7 hours, cooled and distilled of the excess solvent to get the precipitate. The product was dried and recrystalized from alcohol water mixture (1:1).
CNS Depressant activity
The CNS depressant activity of the compounds was studied on mice using pentobarbitone induced sleep method. In this method, mice of either sex weighing 25-30 gm were randomly taken and divided into control, standard and different test groups, each group contain six animals. Group I served as control and treated with normal saline (10 ml/kg, i.p.), group II (standard) treated with standard drug chlorpromazine hydrochloride (1mg/kg, i.m.) 15 min before the administration of pentobarbitone (40mg/kg, i.p.). Test groups III-VIII were treated with (100 mg/kg, i.p). Pentobarbitone (40mg/kg, i.p.) was administered 30 min later. Onset of sleep and duration of sleep measured for the entire group. Onset of action was recorded by noting the time of loss of reflex for three consecutive trials, duration of sleep recorded by time difference between loss of righting reflex and recovery time.
Scheme-1
Scheme-2
Table-1 Spectral data of Mannich bases
|
|
λmax.(nm) |
1 H NMR |
Mass |
|
Piperazine |
211 |
8.3 (s)1H of CONH, 8.35-8.33 (m) 2H of aromatic ring, 8.33-8.16(m) 2H of aromatic ring, 7.6-7.4 (m) 2H of aromatic ring, 7.3-7.21 (m) 3 H of aromatic ring,7.69 (s) 1H of thiophene, 4.3-4.2 (m) 2H of CH2 and 1H of NH, 3.3 (s) 2H of CH2, 2.1 (m) 4H of CH2, 1.9 (m) 4H of CH2
|
|
|
Morpholine |
|
|
388 |
|
3’ chloro, 4’fluoro aniline |
218 |
|
|
|
4’ fluoro aniline |
254 |
8.3 (s)1H of CONH, 8.35-8.33 (m) 2H of aromatic ring, 8.33-8.16(m) 2H of aromatic ring, 7.6-7.4 (m) 2H of aromatic ring, 7.3-7.21 (m) 3 H of aromatic ring,7.69 (s) 1H of thiophene, 4.3-4.2 (m) 2H of CH2 and 1H of NH, 3.3 (s) 2H of CH2, 2.1 (s) 3H of CH3.
|
398 |
|
2’ fluoro aniline |
235 |
|
398 |
|
m toluidine
|
251
|
8.6 (s) 1H of CONH, 7.98-7.8 (m) 2H of aromatic ring, 7.7-7.6 (m) 2H of aromatic ring, 7.43-7.2 (m) 3H of aromatic ring, 7.1-7.0(m) 1H of aromatic ring, 7-6.9 1H of aromatic ring and 1H of thiophene, 4.3-4.2 (m) 2H of CH2 and 1H of NH,3.9 (s) 2H of CH2, 2.7 (s) 3H of CH3, 2.3 (s) 3H of CH3.
|
|
|
o toluidine |
267 |
|
432 |
|
p toluidine |
283 |
8.6 (s) 1H of CONH, 7.98-7.8 (m) 2H of aromatic ring, 7.7-7.6 (m) 2H of aromatic ring, 7.43-7.2 (m) 3H of aromatic ring, 7.1-7.0(m) 1H of aromatic ring, 7-6.8 1H of aromatic ring and 1H of thiophene, 4.3-4.0(m) 2H of CH2 and 1H of NH,3.7 (s) 2H of CH2, 2.8 (s) 3H of CH3, 2.1 (s) 3H of CH3.
|
|
Table 2 Prolongation of pentobarbital-induced sleeping time by the compound SBJ-Ia-l
|
R |
Dose (mg/kg) |
Onset of sleep(min) |
Duration of Sleep (min) |
|
Piperazine |
100 |
10.00±0.01 |
32.05±1.02 |
|
Morpholine |
100 |
8.7±0.08 |
22±1.00 |
|
3’ chloro, 4’fluoro aniline |
100 |
13.1±0.02 |
30.00±0.07 |
|
4’ fluoro aniline |
100 |
13.6±0.29 |
25.50±1.06 |
|
2’ fluoro aniline |
100 |
11.5±0.02 |
19.75±0.135 |
|
m toluidine |
100 |
7.0±0.63 |
28±0.04 |
|
o toluidine |
100 |
8.0±0.63 |
29.75±0.135 |
|
p toluidine |
100 |
7.2±0.63 |
25±0.04 |
|
Chlorpromazine |
1 |
3.75±0.43 |
161.00±1.58 |
|
Pentobarbitone |
40 |
5.50±0.29 |
96.25±0.95 |
Values are expressed in Mean±SEM, n = 6, *Indicates significant difference at p<0.001 when compared to control
RESULT AND DISCUSSION:
The result of pentobarbitone induced sleeping time test showed that the newly synthesized derivatives have moderate to good CNS depressant activity. Table 2 showed that compounds with electron donating group at dose 100mg/kg produced significant reduction in the onset and prolongation of sleep duration induced by pentobarbitone. The other derivatives also showed comparable result to that of the standard drug chlorpromazine.
ACKNOWLEDGEMENT:
The authors are thankful to Management, PES College of Pharmacy for providing necessary facilities.
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Received on 11.02.2013 Modified on 15.02.2013
Accepted on 06.03.2013 © AJRC All right reserved
Asian J. Research Chem. 6(3): March 2013; Page 244-247