Synthesis and Characterization of Benzimidazole by Using o-Phenylenediamine with Different Aldehydes and Carboxylic Acids in the Presence of ρ-TSOH as a Catalyst

This research paper deals with the synthesis and diagnose of Benzimidazole rings which were have been prepared by using two different methods in which used starting material o-phenylenediamine with different compounds. The first method is with aldehydes such as 4-Chlorobenzaldehyde, 4-N, N-Dimethylbenzaldehyde, and Formaldehyde. The second is with carboxylic acids such as salicylic acid, acetic acid, and butanoic acid. ρ-TSOH has been using as a catalyst in the synthesis methods above and used F.T.I.R and HNMR spectroscopy are used for diagnosing the prepared rings in addition to the physical properties.


INTRODUCTION
Benzimidazole is one of the heterocyclic compounds that shows different biological qualities such as antibacterial and antifungal 1 .Also, some Benzimidazoles have an effect on human viruses such as cytomegalovirus 2 .There are two procedures for the synthesis of 2-substituted Benzimidazoles.The first is the reaction of phenylenediamines and carboxylic acids or its derivatives by heating 3 in strong drying conditions 4 .The second includes a two-step procedure that includes the oxidative cyclodehydrogenation of Schiff bases, which are often generated from the condensation of phenylenediamines and aldehydes 3 and with aryl-aldehydes by using an acidic agent and also with silica gel at room temperature 4 .ρ-TsOH has been used as a neutral acid catalyst to synthesize a number of benzimidazoles 5 .It is considered as an important, effective, available and inexpensive incentive 6 .Also, there are many ways to synthesize benzimidazole by using different catalysts such as Nanocrystalline oxides with iodine 7 , H 2 O 2 /HCl and Cu(OTf) 2 8 , HCl 9 .In this work, the aim was the synthesis of benzimidazole rings by using one catalyst is ρ-TsOH as in previous studies above, which have used one catalyst in different circumstances.

ExPERIMENTAL The General Method for Synthesizing Benzimidazoles from Aldehydes
A solution of Aldehyde (0.01 mole), o-phenylenediamine(0.01 mol) and DMF (3 ml) has been mixed with ρ-TsOH (20 ml).The mixture has been heated and stirred at 80C o for 2-3 h then cooled to reach room temperature, the mixture has been added dropwise with stirring into mixture of Na 2 CO 3 (0, 01mole) and H 2 O (20 ml), the product has been filtered, washed by H 2 O, then dried 2 to yield A, B and C compounds.

The General Method for Synthesizing Benzimidazole from Carboxylic Acids
A solution of Carboxylic acid (0.01 mole), o-phenylenediamine(0.01 mole) and toluene (10 ml) has been mixed with ρ-TsOH (20 ml).The mixture has been refluxed for 2-3 h then cooled, filtered and dried 10 to yield D, E and F compounds.

RESULT AND DISCUSSION
Synthesis compounds characterized by F.T.I.R. and H-NMR spectroscopy have showed an important absorption packs of functional groups for the synthesis Benzimidazole derivatives from aldehydes and carboxylic acids with presence of ρ-T S OH as a catalyst in the different conditions.
and appearance of an absorption pack at 1157 cm -1 refers to (C-O) bond in addition to an absorption pack (N-H) group at 3240 cm -1 .HNMR (400 MHz ) δ(ppm)