Synthesis and Characterization of 3-(1-Hydroxy Naphthalene-2-yl)-5-(Furan-2-yl)-1-Substituted  Pyrazolines

Introduction

The literature survey reveals that pyrazoline derivatives have been studied extensively because of their ready accessibility, diverse chemical reactivity, broad spectrum of biological activity^6-8and variety of Industrial applications.^9,10 Pyrazolines with sulphonamidoaryl substituent  at 3-position show cerebroprotective¹¹, antidepressant activity¹² , anti-implantation activity¹³, hypoglycemic activity¹⁴. Due to this  vital biological roll of pyrazoline derivatives, it was thought of interest  to synthesize titled pyrazoline derivatives . Thus we present herein the synthesis of the titled compounds. It has been observed that substituted flavanones are the best starting compounds for the preparation of 4-aroyl derivatives of pyrazoline. Present work deals with the synthesis of some new pyrazolines and their characterization by spectral analysis ( IR, ¹H NMR )

EXPERIMENTAL

All the melting points were taken in silicon oil bath with open capillary tubes and are uncorrected. 1 H NMR spectra were recorded on a Brucker AC300 FNMR spectrometer(300MHz), using TMS as an internal standard. IR spectra were recorded on a Nicolet-Impact 400 FT-IR spectrometer. Thin Layer Chromatography on silica gel-G, was used to check the purity of the compounds. Microanalysis of nitrogen was obtained on Colman 29-N analyzer.

Experimental Section

Procedure for the synthesis of  2-acetyl-1-naphthol  2

In hot glacial acetic acid (80ml), fused ZnCl2(50 gm) was added and refluxed till dissolved, then powdered 1-naphthol (30gm )was added and the mixture was refluxed for about 8 hours then cooled & poured in acidulated water. The solid obtained was filtered, washed, dried and recrystallized from rectified spirit to obtain compound 2. Physical data of the compound is given in table 1

2: IR (KBr) : 1650 (C=O), 3412 (-OH) NMR (CDCl3 + DMSO-d6) : δ 2.35 (S,3H,CH3), δ 7.11-6.88 (m, 6H, Ar-H), δ 9.83 (S,1H,-OH)

Synthesis of 1-(1-hydroxy naphthalen-2-yl)-3-(furan-2-yl) prop-2-ene-1-one (3):

2-acetyl-1-naphthol ( 0.01mole ) and furfuraldehyde (0.02 mole) were added in ethanol solvent (20ml). To this mixture KOH (10%, 10ml) solution was added dropwise with constant stirring. The reaction mixture was kept overnight. Then the mixture was poured over crushed ice & little HCl. The product was filtered and recrystallized from ethanol to obtain the compounds (3). The physical data is given in Table 1
3: IR (KBr):1650 (C=O), 3412(-OH), 1155(C-O-C) NMR (CDCl3 + DMSO-d6) : δ 6.98-7.46 (m,9H,  Ar-H), δ 8.057 (d,1H =CH) , δ 8.099(d,1H =CH)
δ 9.63 (S,1H,-OH)

Synthesis of  3 – ( 1 – hydroxy naphthalen – 2 – yl ) – 5 – ( furan-2-yl ) – 1-substituted pyrazolines(4-8):

1-(1-hydroxy naphthalen-2-yl)-3-(furan-2-yl) prop-2-ene-1-ones (0.01mole) & hydrazine / phenyl hydrazine/ semicarbazide / 2,4 dinitro phenyl hydrazine / isonicotinic acid hydrazide (0.01 mole) were added to DMF (20 ml ) and refluxed for 2 hours . The cooled reaction mixture was diluted with water & the semisolid so obtained was triturated with ethanol to get a solid which was  recrystallised from ethanol–acetic acid mixture to get titled pyrazolines in 45-51% yield . The physical data is given in Table 1

Table 1: Physical and analytical characterization data of newly synthesized compounds

Sr.No.	Compound No	Molecular formula	R	Melting Point  0C	%Yield	% Nitrogen		R.F.Value
						Found	Calculated
1	2	C12H10O2	—	980C	72%	—	—
2	3	C17H12O3	—	1260C	71%	—	—
3	4	C17H14N2O2	H	1100C	38%	10.00	10.07	0.79
4	5	C23H18N2O2	C6H5	1000C	40%	7.81	7.91	0.88
5	6	C18H15N3O3	CONH2	1400C	45%	12.99	13.08	0.87
6	7	C23H16N4O6	C6H3N2O4	1200C	40%	12.56	12.61	0.78
7	8	C23H17N3O3	C5H4NCO	1170C	35%	10.91	10.97	0.84

 

Scheme1: Click here to View Scheme

 

R = H, C₆H₅, CONH₂, C₆H₃N₂O₄, C₅H₄NCO IR, (KBr):3000 (N-H),

3402(-OH), 1151(C-O-C) NMR (CDCl₃ + DMSO-d6) : δ 6.90-7.80 (m,6H,   Ar-H), δ  8.051 (d,1H =CH) , δ 8.091(d,1H =CH) δ 9.62 (S,1H,-OH)

IR (KBr):1600 (C=C), 3410(-OH), 1148(C-O-C) NMR (CDCl₃ + DMSO-d6) :δ 6.89-7.90 (m,11H,   Ar-H), δ  8.049 (d,1H =CH) , δ 8.081(d,1H =CH) δ 9.53 (S,1H,-OH).

IR (KBr):1723 (C=O), 3405(-OH), 1160(C-O-C) NMR (CDCl₃ + DMSO-d6) : δ 6.81-7.40 (m,6H,   Ar-H), δ  8.041 (d,1H =CH) , δ 8.079(d,1H =CH) δ 9.49 (S,1H,-OH), 6.6 (S,2H,NH₂).

IR(KBr):1530,1550(NO₂),3412(OH),1155(C-O-C) NMR (CDCl₃ + DMSO-d6) : δ 6.81-7.60 (m,9H, Ar-H), δ  8.045 (d,1H =CH) , δ 8.081(d,1H =CH) δ 9.43 (S,1H,-OH).

IR (KBr):1611 (C=O), 3477(-OH), 1170(C-O-C) NMR(CDCl₃ + DMSO-d6) : δ 6.95-7.81 (m,10H, Ar-H), δ  8.043 (d,1H =CH) , δ 8.083(d,1H =CH) δ 9.50 (S,1H,-OH).

ACKNOWLEDGEMENT

The author is  thankful to the Director, Govt. Vidarbha Institute of Science and Humanities, Amravati.

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