https://www.science.gov/topicpages/s/schiff+base+anions.html

hello, you can prepare it in two ways :1. in alcoholic medium

2. in acetic acid medium

you can read my procedure in my articles

1-Synthesis, Characterization and Biological Evaluation of Penicillin

Derivatives Complexes with Some Transition Metal Ions

2-Synthesis and Characterization of New Complexes of (N-P-Amino Diphenyl Amine) Amino (2-Hydroxy Phenyl) Acetonitrile Ligand with Some Transition Metal Ions

1.1 Solvent based synthesis

Solvent based Schiff base synthesis generally requires appropriate solvent like ethanol or methanol and mixture is refluxed under pressure by applying acidic, basic or neutral medium. The first preparation of Schiff base was reported in the 19th century by Schiff (1864).. The classical synthesis reported by Schiff involves the condensation of a carbonyl compound with an amine under azeotropic distillation [6]. Molecular sieves are then used to completely remove water formed in the system [7]. In the 1990s an insitu method for water elimination was developed, using dehydrating solvents such as tetramethyl orthosilicate or trimethyl orthoformate [8,9]. In 2004, Chakraborti et al. [10] demonstrated that the efficiency of these methods is dependent on the use of highly electrophilic carbonyl compounds and strongly nucleophilic amines. Presence of water may reverse the reaction by hydrolyzing the Schiff base.

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Scheme. Solvent based synthesis of Schiff base

1.2 Solvent free synthesis by microwave irradiation

The microwave –assisted synthesis of Schiff base from Salicyldehyde and different aryl amines is performed efficiently and get high yield of products in short time [2]. This is carried in an oven, Midea PJ21B-A 800W and is subjected to microwave for an optimized time on the "M-High" setting.

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Scheme : Solvent free synthesis by microwave irradiation

The solvent free organic synthesis mediated by microwave irradiation performs several economies such as low risk of hazard, time economy and environmental friendship. Purification by simple recrystallization technique offers less contamination.

1.3 Solvent free synthesis by using Catalyst

Solvent free synthesis of Schiff bases obtained from 4,5-diazafluuoren-9-one with substituted amines is done efficiently at room temperature by using SnCl2 catalyst [4]. The reaction mixture is grinded in a mortar with the help of pestle and the progress reaction is monitored by TLC and column chromatography

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Scheme : Solvent free synthesis by using Catalyst

1.4 Solvent and catalyst free synthesis

A mixture of Substituted aromatic amines and substituted aromatic aldehydes is grinded in a mortar with a pestle made of porcelain and the progress of reaction is monitored by TLC. The crude product of Schiff base is purified by column chromatography. The completion of reaction takes place within 2-3 minutes. However the synthesis of Schiff bases from ketone requires acetic acid as a catalyst [5].

📷Scheme : Solvent and catalyst free synthesis

[2] Yang H. J., Sun W. H., Li Z. L. and Zhi M.A.; The rapid synthesis of Schiff base without solvent under microwave irradiation, Chinese chemical Letters, 13 (2002) 3-6.

[3] Bukhari I.H., Arif M., Akbar J. and Khan A.H.; Preparation, characterization and biological evaluation of Schiff base transition metal complexes with Cephadrine; Pakistan Journal of biological sciences, 8 (2005) 614-617.

[4] Shaikh K. A., Patil V. A. and Ahmed A.; An environmentally benign, solvent free synthesis and antibacterial activity of novel Schiff bases derived from 4,5-diazafluoren-9-one, Elixir org. chem., 45 (2012) 7881-7883.

[5] Shaikh K. A., Patil V. A. and Zamir A. M.; Solid phase promoted greener synthesis and

antibacterial activity of novel Schiff base under catalytically free condition, Elixir org. chem., 43 (2012) 6960-6963.

[6] Moffett R.B., Rabjohn N, editor. Organic synthesis, New York (USA); John Willey and Sons, Inc; 4 (1963 ) 605-608.

[7] Taguchi K. and Weitheimer F.H., Catalysis by molecular sieves in the preparation of Ketimines and enamines. J. org. chem., 36 (1971) 1570-1572.

[8] Love B.E. and Ren J. , Synthesis of sterically hindered imines; J org. chem.. 58(1993)5556-5557

[9] Look G.C., Murphy M.M., Campbell D.A. and Gallop M.A.; Trimethylorthoformate: a mild and effective dehydrating reagent for solution and solid phase imine formation, Tetrahedron Lett., 36 (1995) 2937-2940.

[10] Chabraborti A.K., Bhagat S. and Rudrawar S.; Magnesium perchlorate as an effective catalyst for the synthesis of Imines and Polyhydrazones, Tetrahedron Lett., 45 (2004) 7641-7644.

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