INTRODUCTION:

Azo compounds constitute one of the largest and oldest classes of industrially synthesized organic compounds and are widely used even now. They are important in drugs and cosmetics¹and show a variety of interesting biological activities. Some azo compounds have shown a good antibacterial activity^2-7. The existence of an azo moiety in different types of compounds has caused them to show pesticidal activity⁸. It has been also noted for its high carcinogenic activity⁹. Azo compounds have been used for a long time as dyes in industry¹⁰. In addition, azo compounds are used in analytical chemistry as indicators in pH, redox, or complexometric titrations^11-12.

EXPERIMENTAL:

Melting points were determined in open capillary tubes and are uncorrected. The purity of the compound was checked on silica-gel-coated Al plates (Merck). IR spectra were recorded in KBr on a Perkin Elmer Spectrum RX-1 FT-IR spectrophotometer. ¹H-NMR spectra was measured on Advance Bruker DRX-300 and JEOL AL300 FTNMR using solution in hexadeuterio dimethyl sulfoxide (DMSO) with trimethyl silane(TMS) as the internal standard , chemical shifts are given in δ (ppm). Nitrogen was estimated by Dumas method. All chemicals were of analytical grade.

General procedure:

Synthesis of 3-Cl-4-F azo salicylaldehyde (I):

3-Cl-4-F aniline (0.01mole, 1.455g) was dissolved in a mixture of concentrated HCl (8 ml) and water (6 ml) and cooled to 0^oC in an ice bath.

To it a cold aqueous solution of sodium nitrate (0.03 mole) was added. The diazonium salt solution was added dropwise into a 0^oC cooled solution of salicylaldehyde(0.01 mole) and NaOH solution(40%). The resulting solid was washed with water and recrystallized with absolute ethanol.

Scheme A

Synthesis of Ethyl 2,3-di oxo butyrate-2-(substituted) phenyl hydrazone (IIa-e): Substituted aniline (3-Cl-4-F, 2-nitro, 3-nitro, 4-nitro and 2,4-dinitro)(0.01mole) was dissolved in a mixture of concentrated HCl (8 ml) and water (6 ml) and cooled to 0^oC in an ice bath. To it a cold aqueous solution of sodium nitrate (0.03 mole) was added. The diazonium salt solution was added dropwise into a cooled solution of ethylacetoacetate (0.01 mole) and sodium acetate (0.12 mole) in ethanol (50 ml). The resulting solid was washed with water and recrystallized with absolute ethanol.

Scheme B

Table-I Physical and analytical data of compounds

S. No	R	Mol. Formula	Color	M.P (^oC)	Yield %	N % Found (Calc.)
I	3-Cl-4-F	C₁₃H₈N₂O₂FCl	Orange	120	89.96	10.11 (10.05)
IIa	3-Cl-4-F	C₁₂H₁₂N₂O₃FCl	Reddish brown	102	90.09	9.86 (9.77)
IIb	2-NO₂	C₁₂H₁₃N₃O₅	Yellow	194	67.02	14.93 (15.05)
IIc	3-NO₂	C₁₂H₁₃N₃O₅	Muddy Yellow	213	78.14	14.98 (15.05)
IId	4-NO₂	C₁₂H₁₃N₃O₅	Yellow	222	73.83	15.13 (15.05)
IIe	2,4-diNO₂	C₁₂H₁₂N₄O₇	Yellow	158	82.41	17.22 (17.28)
IIIa	3-Cl-4-F	C₁₃H₈N₂O₂FCl	Yellowish Orange	140	81.25	10.88 (10.92)
IIIb	2-NO₂	C₁₁H₁₁N₃O₄	Yellow	172	78.23	16.76 (16.87)
IIIc	3-NO₂	C₁₁H₁₁N₃O₄	Yellow	132	85.48	16.91 (16.87)
IIId	4-NO₂	C₁₁H₁₁N₃O₄	Yellow	223	81.05	16.95 (16.87)
III e	2,4- diNO₂	C₁₁H₁₀N₄O₆	Yellow	152	75.59	19.00 (19.05)

Table- II Characterization (IR and ¹H NMR) data of compounds

Compound No.	IR (ν in cm^-1)	¹H NMR (δ in ppm)
I	746 (C-Cl), 1174 (C-F), 1481 (N=N), 1620 (Ar-(C-C)), 1655 (C=O), 3414 (-OH)	2.51 (DMSO), 3.35 (DMSO H₂O), 7.04-7.38 (m, 3H, Ar-H), 7.60-8.18 (m, 3H, Ar-H), 10.36 (s, 1H, CHO), 11.63(s, 1H, OH).
IIa	870 (C-Cl), 1019 (C-F), 1048 (-N-N-), 1525 (Ar-C-H), 1680 (C=O), 2361 (CO₂), 3449 (-NH)	1.27 (s, 3H, CH₂CH₃), 2.38 (s, 3H, COCH₃), 2.50 (DMSO), 3.34 (s, 1H, CH), 4.26 (s, 2H, COOCH₂), 7.41-7.74 (m, 3H, Ar-H).
IIIa	1027 (C-Cl), 1182 (C-F), 1260 (C-N), 1420 (C-H), 1516 (C=N), 1633 (Ar C-C), 1735 (C=O), 3465 (N-H)	2.42 (s, 6H, 2CH₃), 2.50 (DMSO), 3.33 (s, 1H, CH), 7.45-7.51 (t, 1H, Ar-H), 7.60-7.62 (d, 1H, Ar-H), 7.80-7.82 (d, 1H, Ar-H).

Synthesis of 2,4-di keto-3-(substituted phenyl azo) pentane (IIIa-e): Substituted aniline (3-Cl-4-F, 2-nitro, 3-nitro, 4-nitro and 2,4-dinitro)(0.01mole) was dissolved in a mixture of concentrated HCl (8 ml) and water (6 ml) and cooled to 0^oC in an ice bath. To it a cold aqueous solution of sodium nitrate (0.03 mole) was added. The diazonium salt solution was added dropwise into a cooled solution of acetyl acetone (0.01 mole) and sodium acetate (0.12 mole) in ethanol (50 ml). The resulting solid was washed with water and recrystallized with absolute ethanol.

Scheme C

ACKNOWLEDGEMENTS:

We are thankful to Central Drug Research Institute (CDRI), Lucknow and CISC, BHU for spectral analysis. We are also very grateful to Dr. Ajay Taneja, Reader, Department of Chemistry, St. John’s College, Agra for his encouragement and valuable discussions.

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Received on 03.11.2009 Modified on 05.12.2009

Asian J. Research Chem. 3(2): April- June 2010; Page 428-429