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Multicomponent Reactions with Carbonyl Compounds

Schiff base are derived by condensation reaction of aldehyde or ketones or primary amine and these containing azomethine (RCH=N) group. Many Schiff base ligands have been synthesised from heterocyclic compounds 2. The heterocyclic ring contained sulphur, nitrogen and oxygen import special biological activity 3-8 to Schiff base and their metal complexes. The coordinating property of Schiff base with 4- aminoantipyrine has a variety of applications in the biological, clinical, analytical and pharmacological areas 9-10. Aminoantipyrine is very much used in medicine 2 and it is believed that its amino derivative would equally be of much use in medicine possibly as intermediate in antipyretic and analgesic drugs 11.

Synthesis of N -Heterocycles - Organic Chemistry Portal

Several publications have been reported on design and synthesis of new compounds as antitubercular agents,. It is observed that the synthesized dihydropyrimidine derivative by utilizing Biginelli reaction has shown prominent antitubercular activity against H37Rv using Microplate Alamar Blue Assay (MABA). From these results, valuable data about the structure activity correlations of the tested compounds were deduced. Incorporation of chlorine atom at the 4-position of (compound IVf) led to significant activity against (MIC = 6.2±0.36 μg mL–1), suggesting that the presence of a strong electron withdrawing group was favourable to the activity. Incorporation of an unsubstituted phenyl group led to complete loss of activity.

Volume 94 (2017) Preface Scott E

In present context, bidentate ligand from condensing 4-amionoantpyrine with Biginelliadduct of salicylaldehyde was synthesised. The synthesised compound and its chelation behaviour with metal ions were studied through physical parameters and spectral analysis. The in vitro antimicrobial properties of ligand and metal complexes were also investigated.

A thorough search of literature reveals that no work has been done on the transition metal complexes of Schiff base condensed by 4-aminoantipyrine with Biginelli reaction through salicylaldehyde which is a characteristic aroma component of buck wheat 12 and have good antimicrobial activity against certain bacteria or fungi 13. Moreover Biginelli reactions (Multi component reactions) are of increasing importance in the organic and medicinal chemistry due to their high degree of atom economy, applications in the combinatorial chemistry and diversity oriented synthesis 14.

Monomer Chem's Name Reaction List

Conventional method: To a mixture of β-ketoester (0.01 mol, I), substituted aromatic aldehyde (0.01 mol, II), urea or thiourea (0.01 mol, III) and sodium dodecyl sulphate (10% w/v in water) were heated under reflux for 4-5 h with magnetic stirring. After completion of the reaction as monitored by TLC, the reaction mixture was poured into ice-cold water and stirred for 10-15 min. The contents of the flask were then filtered, washed with cold water (20 mL) to remove excess urea/thiourea. The solid so obtained was the corresponding dihydropyrimidines (IV) and recrystallized by hot ethanol to get the pure products (). Physical data of synthesized compounds are presented in .


RESULTS AND DISCUSSION

Chemistry: The biginelli protocol for the preparation of DHPMs consisted of heating a mixture of three components which included β-ketoester, aldehyde and urea in ethanol containing a catalytic amount of HCl. The major drawback associated with this protocol was the use of strong acid as well as the low yields in the case of substituted aromatic and aliphatic aldehydes. To enhance the efficiency of the biginelli reaction, various catalysts and reaction conditions have been studied including classical conditions with ultrasound or microwave-assisted irradiations solid-support, ionic liquids, Lewis acid catalysts such as LiBr, NH4Cl, MgBr2 and CaF2. On the other hand, a number of the reported protocols for the synthesis of DHPMs required solvents and catalysts which are not acceptable in the context of green synthesis, utilization of reagents and catalysts which are either toxic or expensive and stoichiometric use of reagents with respect to reactant. Here the capacity of SDS as potential catalyst for one-pot synthesis of 3,4-dihydropyrimidinones was reported.

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DRUG DELIVERY SYSTEMS – All About Drugs

The 4-(substituted phenyl-)-3,4-dihydropyrimidine-2-(1H)-ones/thiones (IVa-IVo) were prepared using one pot Biginelli reaction using sodium doceyl sulphate as catalyst and water as solvent as depicted in . The IR spectra of the compound IVa showed the absorption bands at 3241, 2985 and 1713 cm–1 due to presence of -NH, Ar-H and C=O groups respectively. The 1H-NMR spectra showed signals at δ 2.29 (s, -COCH3), 7.24 (m, Ar-H), 7.82 and 9.12 (br, -NH) and the mass spectra showed M+1 peak at 231 with its molecular formula C13H14N2O2.

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