SYNTHESIS OF SCHIFF BASES DERIVED FROM 5-FORMYL ETHYLVANILLIN

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1 SYNTHESIS OF SCHIFF BASES DERIVED FROM -FORMYL ETHYLVANILLIN A. Nicolae and A. Anghel abstract: In the reaction between -formyl ethylvanillin and aromatic amines in equimolecular ratio, Schiff bases are formed with raised yields. By the Schiff bases formation,, can be observed, that from the two carbonyl groups of the -formyl ethylvanillin molecule, the formyl group situated in the ortho position towards the hydroxyl group is more reactive. The synthesized Schiff bases were characterized by means of IR, H-, and C-NMR spectra. Introduction Schiff bases are organic compounds with great utility in important fields as: medicine agriculture, cosmetic products [ ]. Some Schiff bases present anticancer [2], antitumor [3], antibacterial [] activity; they play a prominent part in the enzymatic or unenzymatic transaminating reactions of the carbonyl compounds with amino acids []. In the coordinate chemistry field, a lot of Schiff bases operate as ligands [7,]. Some of the Schiff bases complex combinations with metals are used as insecticides, fungicides, herbicides []. Can be remarked the large field of the biological action presented by the Schiff bases derived from aromatic 2-hydroxyaldehydes []. In order to obtain new compounds having practical importance, a series of Schiff bases derived from -formyl ethylvanillin were synthesized. Experimental Melting points were determined in open capillary and are uncorrected. The IR spectra were recorded with a FTS -Biorad spectrophotometer, in KBr pellets. The NMR spectra were registered on Varian Gemini 300 and Varian EM30L NMR, 0 MHz. spectrometers, using CDCl 3 as solvent and TMS as internal standard. The purity of each compound was verified by TLC- silica gel plates (Merck). The elution was realized in the chloroform-methanol : (V/V). The spots visualization was done either with UV light ( = 2 nm) or with iodine vapour. University of Bucharest, Dept. of Organic Chemistry, Faculty of Chemistry, 0-2 Road, Panduri, Bucharest, Romania Analele Universit ii din Bucure ti Chimie, Anul XII (serie nou ), vol. I-II, pag. Copyright Analele Universit ii din Bucure ti

2 0 A. NICOLAE A. ANGHEL General procedure for the Schiff bases synthesis 0.0 moles of -formyl ethylvanillin were solved in 20 ml anhydrous ethanol, keeping warm conditions. To the room temperature cooled solution are added by dropping 0.0 moles aromatic amine solved in 20 0 ml anhydrous ethanol, corresponding to the amine solubility. After 2 hours, the formed crystals are filtrated, washed with some methanol and dried. The reaction yields, the melting points and the recrystallization solvents for the obtained Schiff bases are presented in the Table. N (3 -formyl- - ethoxy- -hydroxybenzyliden)aniline I CH N 8 7 IR(CHCl 3 :( C=O);( C=N), 0,82,0 (benzene rings) 3( C 2 H -O-C aromatic); ( C-). H-NMR(CDCl 3, 30 MHz, ppm, J, Hz):.(t.., 3H, H-);.(q,., 2H, H-); (m,3H,H-2, H-,H-); 7.3(d,.8, H, H-); 7.3(d,.8, H, H-); 7.(m, 2H, H- 3, H-); 8.70(s, H, H-7);.83(s, H, H-). C-NMR(CDCl 3, 30 MHz, d, ppm):.(ch 3, C-);.0(C-);.0(C-); 7.(Cq,C-8);0.8(C-2;C-);7.(Cq,C-);7.7(C-);.72(C-3,C-);.0(C-);.8(C-);.37(Cq, C-); 0.(C-7);.0(Cq, C-); 8.(C-). Anal. Calcd. for C H O 3 N: N,.20; Found: N,.28 -Methyl-N(3 - formyl- - ethoxy- -hydroxybenzyliden)aniline II CH N CH 3 IR(CHCl 3, cm ):(( C=O); ( C=N);80,7,7 (benzene rings); 3( C 2 H -O-C aromatic) ( C-) H-NMR(CDCl 3, 30 MHz, ppm, J, Hz):.3(t, 7.0, 3H, H-); 2.0(s, 3H,H-7);.8(q, 7.0,2H, H-); 7.23(d, 8.8, 2H, H-2, H-); 7.2(d, 8.8, 2H, H-3, H-); 7.(d,.8, H, H-); 7.(d,.8, H, H- ); 8.(s, H, H-7);.8(s, H, H- ). C-NMR(CDCl 3, 30 MHz, ppm):.(ch 3, C-); 2.0(C-7);.8(C-);.(C-); 7.28(Cq, C-8); 0.(C-2, C-); 7.32(Cq, C-); 0.0(C-;

3 SYNTHESIS OF SCHIFF BASES DERIVED FROM -FORMYL ETHYLVANILLIN 0.27(C-3, C-); 7.(Cq, C-); 2.38(Cq, C-);.(Cq, C-);.3(C-7);.(Cq, C-); 8.(C-). Anal. Calcd. for C 7 H 7 O 3 N: N,.; Found: N, Methyl-N(3 - formyl- - ethoxy- -hydroxybenzyliden)aniline III H 3 C H 2 CO 8 7 CH N 7 CH 3 Anal. Calcd. for C 7 H 7 O 3 N: N,.; Found: N,.. IR(CHCl 3, cm ): (( C=O); ( C=N);0,78,3 (benzene rings); 8( C 2 H -O- C aromatic); ( C-). -Hydroxy-N(3 - formyl- - ethoxy- -hydroxybenzyliden)aniline IV CH N 8 7 Anal. Calcd. for C H O N: N,.; Found: N,. -Methoxy-N(3 - formyl- - ethoxy- -hydroxybenzyliden)aniline V CH N OCH H-NMR(CDCl 3, 0 MHz, ppm, J, Hz):.3(t, 7.0, 3H, H- ); 3.(s, H, H-7);.(q, 7.0, 2H, H-); (m, H, H-3-H-, H-, H-); 8.(s, H, H-7);.77(s,H, H-). IR(CHCl 3, cm ): 7(( C=O); 2( C=N);0,80,3 (benzene rings); 8( C 2 H -O-C aromatic); ( C-). H-NMR(DMSO-d, 0 MHz, ppm, J, Hz):.2(t, 7.0, 3H, H- );.7(q, 7.0, 2H, H-); 7.08(dd,,.0, H, H-2, H-3, H-, H-); 7.3(d,.8, 2H, H-, H-); 8.7(s, H, H-7);.8(s, H, H- ). IR(CHCl 3, cm ): 7(( C=O); 7( C=N);87,80,7 (benzene rings); 3( C 2 H -O-C aromatic); ( C-). H-NMR(CDCl 3, 0 MHz, ppm, J, Hz):.3(t, 7.03, 3H, H-); 3,(s, 3H, H-7);.(q, 7.03, 2H, H-); 7.07(dd, 8.8, H, H-2, H-3, H-, H-); 7.3(d,.8, 2H, H-, H-); 8.(s, H-7);.77(s, H, H-).

4 2 A. NICOLAE A. ANGHEL Anal. Calcd. for C 7 H 7 O N: N,.8; Found: N,.8. -Chloro-N(3 - formyl- - ethoxy- -hydroxybenzyliden)aniline VI CH N Cl 8 7 IR(CHCl 3, cm ): 7(( C=O); 7( C=N);80,82,3 (benzene rings); 8( C 2 H -O-C aromatic); ( C-). H-NMR(CDCl 3, 30 MHz, ppm, J, Hz):.3(t, 7.0, 3H, H- );.2(q, 7.0, 2H, H-); 7.2(d,, 8.8, 2H, H-3, H-); 7.2(d, 8.8, 2H, H-2, H); 7.7(d,.8, H-); 7.(d,.8, H- ); 8.(s, H, H-7);.8(s, H, H-). C-NMR(CDCl 3, 30 MHz, ppm, J, Hz):.(C-);.7(C-); 2.7(C-); 7.80(Cq, C-8); 2.2(C-2, C-); 8.0(Cq, C-);.3(C-);.77(C-3, C-); 3.3(Cq, C-);.83(Cq, C-); 8.(Cq, C-); 8.7(Cq, C-);.2(C-7); 8.0(C-). Anal. Calcd. for C H O 3 NCl: N,.; Found: N,.7. -Bromo-N(3 - formyl- - ethoxy- -hydroxybenzyliden)aniline VII CH N Br 8 7 Anal. Calcd. for C H O 3 NBr: N,.02; Found: N,.20 IR(CHCl 3, cm ): 7(( C=O); ( C=N);8,8,3 (benzene rings); 3( C 2 H -O-C aromatic); ( C-). H-NMR(CDCl 3, 0 MHz, ppm, J, Hz):.(t,.8, 3H, H-);.7(q,.8, 2H, H-); 7.(d, 8.0, H, H-2, H-3, H-, H- );7.7(m, 2H, H-, H-); 8.7(s, H, H-7);.8(s, H, H-)

5 SYNTHESIS OF SCHIFF BASES DERIVED FROM -FORMYL ETHYLVANILLIN 3 N-(3 - formyl- - ethoxy- - hydroxybenzyliden) -naphthylamine VIII 8 7 CH N 8a 8 Anal. Calcd. for C 20 H 7 O 3 N: N,.38; Found: N,.. 7 a IR(CHCl 3, cm ):78(( C=O); ( C=N);00,70,70,30 (benzene and naphthalene rings); 8( C 2 H -O-Caromatic); 7( C-). H-NMR(CDCl 3, 0 MHz, ppm, J, Hz):.3(t,.0, 3H, H-8);.8(q,.0, 2H, H-7); (m, H, H- 2, H-3, H-, H-7); (m, 2H, H-, H-); (m, 3H, H-, H-,H-8); 8.(s, H, H-);.7(s, H, H-). N(3 -formyl- - ethoxy- -hydroxybenzyliden) -naphthylamine IX 8 7 CH N 8 8a 7 a IR(CHCl 3, cm - ):8(( C=O); 0( C=N);00,72,0,30 (benzene and naphthalene rings); 3( C 2 H -O-C aromatic); ( C-). H-NMR(CDCl 3, 30 MHz,, ppm, J, Hz):.(t, 7., 3H, H-8);.2(q, 7., 2H, H-7); (m, 2H, H-, H-7); 7.7(d,.8, H, H- ); 7.(d, 8.7 H, H-); 7.(d,.7, H-); 7.(d,.7, H, H-); 7.(dd, 8.7,.8, H-3); 7.87(m, 2H, H-8, H-); 8.70(s, H, H-);.8(s, H, H-) C-NMR(CDCl 3, 30MHz, ppm,):.70(c-8);.7(c-7);.7(c-); 7.(Cq, C-);.3(CH);.(CH); 7.08(CH); 7.(CH); 7.73(Cq, C-); 7.8(CH); 7.(Cq); 8.(CH);.80(CH);.88(C-); 2.(Cq); 3.7(Cq); 2.(Cq);.3(Cq); 0.8(C-); 8.0(C-). Anal. Calcd. for C 20 H 7 O 3 N: N,.38; Found: N,.. Results and Discussion -Formyl ethylvanillin (-hydroxy--ethoxy-isophtalaldehyde) obtained by Duff reaction from ethylvanillin, hexamethylenetetramine in acid medium [], was condensed with aromatic amines in order to obtain Schiff bases (Scheme ).

6 A. NICOLAE A. ANGHEL The reaction of -formyl ethylvanillin with aromatic amines was realized in equimolecular ratio between the reagents. C H N /CH 3 CO 0 % H C 2 O H C 2 O X H 2 N X H C 2 O where: I. X = H; II.X = p.ch 3 ; III.X = o.ch 3 ; IV.X = p.; V.X = p.och 3 ; VI.X = p.cl; VII.X = p.br; VIII.X = C IX.X C H 7 CH N I _ IX Scheme When the Schiff bases are formed one can observe that from the two formyl groups of the -formyl ethylvanillin, more susceptible in the reaction is the group, situated in the ortho position towards the hydroxyl group. The greater reactivity of the formyl group, explained by the possibility to form a chelate with the neighbouring group was also observed in the condensation reactions with bases containing nitrogen and with compounds containing methylene active groups []. In Table the yields reaction and some of the characteristic constants regarding the synthesized Schiff bases are presented. The obtained compounds were characterized by IR and NMR spectra, and their purity was confirmed by thin layer chromatography (TLC) and elemental analysis. By TLC can be observed that the Schiff bases I-IX spots are coloured. Nevertheless the spots visualization is carried out either with iodine, or in ultraviolet light and afterwards with 2,-dinitrophenylhydrazine in order to verify the compounds purity. The synthesized Schiff bases R f values are presented in Table. In the IR spectra of the synthesized Schiff bases, characteristic is the CH=N stretching vibration, which appears as an intense band from 0 to cm. The infrared spectra of the Schiff bases, are observed bands corresponding to the structural elements characteristic for the -formyl ethylvanillin nucleus, namely; the stretching vibration band of the formyl group around 78 cm, the bands for the symmetrical and asymmetrical stretching vibration of the ethoxy group at about cm and cm, the C stretching vibrations at 7cm and at cm. Besides these bands, appear also bands characteristic for the aromatic nucleus of the synthesized products (00 80 cm, cm,3 0 cm ). In the range at cm are superposed a lot of vibrations characteristic both aromatic nucleus and Ar-N, CH from the azomethine group.

7 SYNTHESIS OF SCHIFF BASES DERIVED FROM -FORMYL ETHYLVANILLIN No. No. Compound Table. Characteristic constants of Schiff bases I-IX M.W. Yield (%) M.P. ( 0 C) (solvent) Cristal colour T.L.C. R f. I (toluene) Red II (ethanol) Yellow III (diethyl ether) Yellow IV (ethanol) Red-orange 0.. V (toluene) Yellow VI (ethanol) Orange VII (toluene) Light red VII (ethanol) Orange 0.7. IX (ethanol) Orange 0.77 The IR absorptions values for each compound are presented in the experimental part. The IR spectra confirm the suggested structures. The molecular structure confirmation of compounds I-IX was realized by the NMR spectra and the main signals are presented for the each compound in the experimental part. The H-NMR spectra of new compounds shows that the chemical shift for the CH=N group appear like a singlet at values between = ppm. There were emphasized signals as triplet for the methyl group protons ( =.. ppm), as quartet for those from ethyl group ( =..2 ppm), as singlet for formyl group proton ( =.77.8 ppm ). The aromatic protons from the two substituted benzene rings are found again in the region = ppm. Also, appear additional signals caused by the substituents from the aniline nucleus. For instance, for the Schiff bases II and III can be observed an additional singlet at = ppm, corresponding to the methyl group protons, and for the compound V, the singlet at = 3. ppm corresponds to the methoxy group protons. In C-NMR spectra, the chemical shifts for the carbon atoms of azomethine group are at =.3.2 ppm, while the carbon atoms from the formyl groups absorbs at = ppm, and the carbon atoms involved in the bond with the hydroxyl group, adjacent to the azomethine group are found again at =.0.3 ppm.the C- NMR spectra were only carried out for the Schiff bases I, II, VI, IX and the chemical shifts are presented in the experimental part. The synthesized Schiff bases belong to a series of compounds, which follow to be tested as ligands in order to obtain coordination compounds with bivalent and trivalent metal ions. Conclusions -Formyl ethylvanillin was condensed with aromatic amines in equimolecular ratio between the reagents, obtaining the corresponding Schiff bases with 8 % yields. When the Schiff bases are formed, one can observe that from the two formyl groups from the -formyl ethylvanillin molecule, more susceptible in the reaction is the group situated in ortho position towards the hydroxyl group.

8 A. NICOLAE A. ANGHEL The structure of the new compounds was confirmed by analytical and spectroscopic methods (IR, H and C- NMR). REFERENCES. Mirkin, M.V. and Bard, A.J. () J. Anal. Chem. 3, Schuster, I.S. and Robert, J.D. (7) J. Org. Chem., Kong, D., Zhang, X., Zhu, Q., Xie, J. and Zhou, X. (8) Zhongguo Yaown Huaxue Zazhi 8(), 2 ; C.A. (),, 30 p.. Rauhut, G., Clark, T. and Steinke, T. (3) J. Amer. Chem. Soc., 7.. Scheehan, J. and Grenda, V.J. (2) J. Amer. Chem. Soc. 8, 27.. Davarski, K., Vasilev, G. and Khalachev, N. (8) Dokl.Bolg.Akad. Nauk 38(), ; C.A. (8), 3, 7 f. 7. Pessoa, J.C., Cavaco, J., Covreia, J., Costa, D., Henriques, R.T. and Gillard, R.D. (2000) Inorg. Chim. Acta. 30(), Zhu, T.L., Tong, J. and Chon, M.X. (2000) J. Chem. Soc. Dalton Trans., 82.. Pui, A and Berdan, I. (2000) Rev. Chim (Bucure ti) 3,.. Alcock, N.W., Cook, D.F., McKenzie, E.D. and Worthington, J.M. (80) Inorg. Chem. Acta 38, 7.. Popp, F.D. () J. Org. Chem. 2,.. Nicolae, A., Dr ghici, C. and David, A. (2003) accepted Rev. Chim. (Bucure ti).