Synthesis and SAR Study of Some New Benzhydryl Piperazine Sulfonamide and Carboxamide as Antimicrobial Agents

Patel R.C *, Patel C.N, Panigrahi B.B. and  Bhaskar V.H.

Department of Pharmaceutical and Medicinal Chemistry, Shri Sarvajanik Pharmacy College, Hemchandracharya North Gujarat University, Near Arvind baug, Mehsana-384001, Gujarat, India.

Department of Pharmaceutical and Medicinal Chemistry, M.P Patel College of Pharmacy, JET, Kapadwanj-387620, Gujarat, India.

*Corresponding Author E-mail: rcpatel_1985@yahoo.co.in

ABSTRACT

Some New benzhydryl piperazine sulfonamide and carboxamide is synthesized from benzaldehyde and phenyl magnesium chloride (Grignard Reagent) under nitrogen atmosphere to give benzhydrol which on treating with thionyl chloride give corresponding benzhydryl chloride which is directly treated with piperazine and anhydrous potassium carbonate using DMF as solvent to give corresponding 1-benzhydryl piperazine. The nucleophilic substitution reaction of 1-benzhydryl piperazine with different substituted aromatic sulfonyl chloride and acid chloride in presence of triethylamine and dichloromethane to give corresponding benzhydryl piperazine sulfonamide and carboxamide. All the title compounds characterised on the basis of their IR, MASS, ¹H NMR spectroscopic data analysis.

KEYWORDS:  Benzhydrol, acid chloride, sulfonyl chloride, antimicrobial screening.

INTRODUCTION:

Some benzhydryl piperazine sulfonamide reported as potent anti-infective agent. Disease caused by microbial infection is a serious meance to the health of human beings and often have connection to some of the other diseases. The scaffold piperazine and its analoges are an important pharmacophore that can be found in biologically active compounds across a number of different therapeutic areas. These include anticancer, antimicrobial, antimalerial, antipsychotic agents, HIV protease inhibitors, antidepressants and antitumour drug against colon, prostate, breast, lung and leukaemia cancers. In 1935 domargk showed the therapeutic value of the sulfonamides. These substances are not specific to group of organism, but are effective against a large variety of pathogenic organisms.

EXPERIMENTAL:

Melting points of all the synthesized compounds were determined in open capillaries and are uncorrected. Thin layer chromatography was performed on microscopic slides (2×7.5cm) coated with Silica-Gel-Gf254 and spots were visualized under UV light and by exposure to iodine vapor.  IR spectra of all compounds were recorded in FTIR 8400S Shimadzu Spectrophotometer using KBr. Mass spectra were obtained using 2010EV LCMS Shimadzu instrument.

The ¹H-NMR was recorded on Bruker Advance-II NMR 400 MHz instruments using CDCl₃ / DMSO-d₆ as solvent and TMS (tetramethylsilane) as internal standard, chemical shifts were expressed as δ values (ppm).

All the chemicals use for the synthesis of titled compounds was produced from S.D. Fine Chem. Ltd, Phenar Chemical Ltd, sigma alderich and Loba Chemicals. The chemicals were used without further purification.

Synthesis of benzhydrol

A solution of 10 ml chlorobenzene, magnesium metal 2.4 gm (0.1M) and 15 ml dry ether was taken in 250 ml flate bottom flask provided with mechanical stirrer and a guard tube. The temperature of the mixture was maintained at about 0-5˚C. Nitrogen environment was provided and the mixture was stirred vigorously. 10 ml (0.1M) of benzaldehyde and 7-10 ml THF was added slowly. The reaction mixture was refluxed for 6 hr. Then the resulting mixture was placed in crushed ice, extracted two times with 25ml ether; the ether was evaporated to obtain magnesium chloride diphenyl methanolate. Crude benzhydrol was worked up with conc HCl, the mixture was boiled and neutralized with NaOH solution (30% w/v) to get the crystalline precipitate to separate out. The product was recrystallized from rectified spirit, yielded 10gm (60%) of crystalline product, MP 65-68˚ C.

Table- 1. Physicochemical data of the compounds (4a-c):

Compd. code	R	Mol. Formulae	M.P.	Yield (%w/w)	Rf ^a
4a	2-nitrophenyl	C23H23N3O4S	160-162 ^0C	75	0.60
4b	4-methylphenyl	C24H26N2O2S	190-195 ^0C	70	0.58
4c	4-methoxyphenyl	C24H26N2O3S	198-200 ^0C	65	0.55

Table- 2. Physicochemical data of the compounds (5a-c):

Compd. code	R	Mol. Formulae	M.P.	Yield (%w/w)	Rf ^a
5a	2- chlorophenyl,	C24H23ClN2O	>270 ^0C	60	0.63
5b	4-chlorophenyl	C24H23ClN2O	.275 ^0C	65	0.65
5c	4-methoxyphenyl	C25H25N2O2	>300 ^0C	65	0.59

Mobile phase Hexane: Ethyl acetate (8:2)

Table -3. Spectral data of the compounds (4a-c):

Compd. Code	Mol. Wt. (g/mol)	I.R (cm^-1, KBr)	Mass (m/e)	^1H NMR (DMSO-d6,  ppm)
4a	437.51	-3109 (-CH) -1529 (NO2) -1350 (SO2)	438 (M^+) 439 (M^+2)	2.4 (T, 4H, piperazine) 3.35 (T, 4H, piperazine) 4.8 (S,1H, -CH ) 6.7-8 (M,14H,Aromatic)
4b	406.54	3106 (CH3) 1355 (SO2)	407 (M^+) 408 (M^+2)	1.53 (S,3H,CH3) 2.48 (T, 4H, piperazine) 3.335 (T, 4H, piperazine) 4.9 (S,1H, -CH ) 6.8-8 (M,14H,Aromatic)
4c	422.54	3135 (-CH) 1360 (SO2) 1280 (-OCH3)	423 (M^+) 424 (M^+2)	1.3 (S,3H,CH3) 2.49 (T, 4H, piperazine) 3.33 (T, 4H, piperazine) 4.95 (S,1H, -CH ) 6.5-8 (M,14H,Aromatic)

Table -3. Spectral data of the compounds (5a-c):

Compd. Code	Mol. Wt. (g/mol)	I.R (cm^-1, KBr)	Mass (m/e)	^1H NMR (DMSO-d6,  ppm)
5a	390.91	2924 (CH) 1651 (-C=O) 722 (Ph)	391 (M^+) 392(M^+2)	2.35 (T, 4H, piperazine) 3.285 (T, 4H, piperazine) 4.65 (S,1H, -CH ) 6.6-7.8 (M,14H,Aromatic)
5b	390.91	2910 (CH) 1635 (-C=O) 715 (Ph)	391 (M^+) 392(M^+2)	2.33 (T, 4H, piperazine) 3.35 (T, 4H, piperazine) 4.6 (S,1H, -CH ) 6.5-7.8 (M,14H,Aromatic)
5c	386.49	3024 (CH) 1670 (-C=O) 1237 (Ph)	387(M^+)	1.4 (S,3H,CH3) 2.5 (T, 4H, piperazine) 3.35 (T, 4H, piperazine) 5.1 (S,1H, -CH ) 6.7-8.1 (M,14H,Aromatic)

Table- 4. Zone of Inhibition measured for test compounds and standard drugs for gram negative bacteria

Compound no	Escherichia coli		Bacillus citrus
	50μg/ml	100μg/ml	50μg/ml	100μg/ml
4a	15	17	14	16
4b	15	17	11	13
4c	11	13	16	21
5a	18	20	20	21
5b	19	20	19	22
5c	16	18	17	20
Streptomycin	20	22	21	23
DMF	-	-	-	-

Table- 5. Zone of Inhibition measured for test compounds and standard drugs for gram positive bacteria

Compound no	Bacillus substillis		Staphylococcus aureus
	50μg/ml	100μg/ml	50μg/ml	100μg/ml
4a	11	12	14	17
4b	14	16	13	16
4c	17	20	11	13
5a	15	19	16	18
5b	14	20	15	19
5c	17	19	14	18
Streptomycin	21	23	22	24
DMF	-	-	-	-

Scheme 1.  synthesis of benzhydryl piperazine sulphonamide and carboxamide

Where, R = 2-nitrophenyl, 4-methylphenyl, 4-methoxyphenyl, R’=2-chlorophenyl, 4-chlorophenyl, 4-methoxyphenyl.

Synthesis of benzhydrylchloride

A solution of benzhydrol (3.68 gm, 0.02M) in dichloromethane 5-7 ml was taken in 250 ml iodine flask provided with mechanical stirrer.

Synthesis of benzhydrylpiperazine

The flask was cooled and thionyl chloride 2.36gm (3ml, 0.02M) was added drop wise with dropping funnel. Than the flask was corked and stirring was continued for about 4hrs.

A solution of benzhydryl chloride (1 ml, 0.005M), piperazine (0.86gm, 0.01M), 5-8 ml DMF and potassium carbonate was taken in RBF and the reaction mixturer was refluxe for 8 hour at 50-60 ˚C. Excess solvent was removed by distillation and on further cooling, crystalline solid was separated, yielded 800 mg (70%).

Synthesis of 1-benzhydryl-4-(2-nitro-benzene sulfonyl)-piperazine (4a):

A solution of 1- benzhydryl-piperazine 0.5 gm (1.98 M,1 eq) in dry dichloro methane was cooled to 0-5 0C in an ice bath. Triethylamine (3 eq) was added to cold reaction mixture and stirred for 10 min then appropriate 2-nitro benzene sulfonyl chloride 0.439 gm (1.98 M, 1 eq) were added and reaction mixture was allowed to stir at room temp for 5-6 hr. The progress of the reaction was monitored by TLC. Upon completion the solvent was removed under reduced pressure and the residue was taken in water and extracted with ethyl acetate. The organic layer was washed with ammonium chloride solution and finally water, and then dried with anhydrous sodium sulphate. The solvent was evaporated to give a crude product 1-benzhydryl-4-(2-nitro-benzene sulfonyl)-piperazine. This was recrystalised from rectified spirit, yielded 650 mg.(75%) m.p.: 160-162^˚C. Similarly compounds (4b-c) were prepared by above method. The characterisation data of these compounds is described in Table-1.

Synthesis of (4-benzhydrylpiperazine-1-yl) (2-Chloro phenyl) methanone (5a):

A solution of 1- benzhydryl-piperazine 0.5 gm (1.98 M, 1 eq) in dry dichloro methane was cooled to 0-50 C in an ice bath. Triethylamine (3 eq) was added to cold reaction mixture and stirred for 10 min then appropriate 2-chloro benzoyl chloride 0.340 gm (1.98 M, 1 eq) were added and reaction mixture was allowed to stir at room temp for 5-6 hr. the progress of the reaction was monitored by TLC.

Upon completion the solvent was removed under reduced pressure and the residue was taken in water and extracted with ethyl acetate. The organic layer was washed with ammonium chloride solution and finally water, and then dried with anhydrous sodium sulphate. The solvent was evaporated to give a crude product (4-benzhydrylpiperazine-1-yl) (2-Chloro phenyl) methanone this was recrystalised with rectified spirit.yeilded 460 mg (60%). m.p.: >27O^˚C. Similarly compounds (5b-c) were prepared by above method. The characterisation data of these compounds is described in Table-2.

Table- 6 Growth of inhibition showing standard drug and synthesized compound

Compound	Concentration of compound
	20μg/ml	30μg/ml	40μg/ml	50μg/ml
4a	-	-	-	-
4b	-	-	+	+
4c	-	-	-	-
5a	-	-	+	+
5b	-	-	-	-
5c	-	-	-	-
griseofulvin	+	+	+	+

ANTIMICROBIAL ACTIVITY:

The synrhesized compounds (4a-c) and (5a-c) were screened for their in vitro antimicrobial activity against Staphylococcus aureus, Bacillus substillis, Bacillus citrus, Escheichio coli, and antifungal activity against Aspargillus nigar by measuring the zone of inhibition in mm. The antimicrobial activity was performed by cup plate method at concentration 50µg/ml and 100µg/ml and reported in Table. Nutrient agar was employed as culture medium and DMF was used as solvent control. Streptomycin and Griseofulvin were used as standard for antibacterial and antifungal activities respectively.

CONCLUSION:

From the antimicrobial screening it was observed that all the compounds exhibited activity against all the organisms employed. Looking at the structure activity relationship marked inhibition in bacteria was observed the compound bearing R = 2-Cl C₆H₄, 4-ClC₆H₄ substituents where as other compounds showed moderate to good activity. Fungicidal screening data also revealed that all the compounds showed moderate to less activity as compared to standard. As we consider all result obtained from antibacterial and antifungal tests together we can say that entire compounds tested are active towards bacteria and fungi.

ACKNOWELEDGEMENT:

The authors are thankful to Department of Pharmaceutical and Medicinal Chemistry and the staff members of Shri Sarvajanik Pharmacy College, Mehsana, Gujarat, India to fulfil the project work successfully.

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Received on 10.06.2009        Modified on 04.08.2009

Accepted on 07.09.2009        © AJRC All right reserved

Asian J. Research Chem. 2(4):Oct.-Dec. 2009 page 448-451