One pot synthesis of Biginelli 3,4-dihydro-1H-pyrimidin-2-ones and 1,2,3,4-tetrahydro pyrimidines

A simple and practical route for the Biginelli cyclocondensation reaction using anhydrous ZnCl2 as a catalyst in n-heptane-toluene medium by reaction of substituted benzaldehydes,1a-d (1a=2-ClC6H4-, 1b=2-BrC6H4- and 1c=4-ClC6H4-,1d=2-H3CC6H4-) with 1, 3-dicarbonyl compounds, 2a-b (2a= ethyl acetoacetate and 2b= acetylacetone) and urea or thiourea, 3a-b to give the corresponding Biginelli 3,4-dihydro- 1H-pyrimidin-2-ones and 1,2,3,4-tetrahydro pyrimidines, 4a-d. The structures of the compounds 4a-d were confirmed by their ultraviolet, infrared, 1H NMR, 13C NMR spectra and elemental analyses. Bangladesh J. Sci. Ind. Res.55(3), 173-180, 2020

SYNTHESIS AND BIOLOGICAL EVALUATION OF SPIRO (INDOLE-THIAZOLIDINE) DERIVATIVES AS ANTIMICROBIAL AGENTS

Objective: The present study aims to synthesize and biological evaluation of Spiro-[Indole-Thiazolidine] derivatives as antimicrobial agents. Methods: The reaction sequence involves microwave-induced preparation of N-(2-oxo-1,2-dihydro-3’H-indol-3-ylidene)pyridine-4-carbohydrazide [3] from isoniazid [1] and isatin [2] followed by the cyclo condensation of [3] and mercaptoacetic acid under microwave condition to achieve the synthesis of spiro-[indole-thiazolidine] derivatives [4]. The resulting compounds were then allowed to react with various aromatic and heterocyclic aromatic aldehydes to afford arylidene derivatives [5a-l]. Result: Isoniazid (1) on condensation with isatin (2) in the presence of catalytic amount of glacial acetic acid furnished N-(2-oxo-1,2-dihydro-3’H-indol-3-ylidene) pyridine-4-carbohydrazide (3), which showed characteristic IR, absorption bands. Compound (3) underwent Spiro cyclization upon its reaction with mercaptoacetic acid in the presence of anhydrous ZnCl2 to form spiro-[indole-thiazolidine] compound (4). Compound (4) was then condensed with aromatic aldehydes to give arylidene derivatives (5a-l), which were characterized by IR and 1H NMR spectral data. Conclusion: All the synthesized compounds were screened for antimicrobial activity by the cup plate method. Most of the derivatives showed good antimicrobial activity against Gram-Positive and Gram-negative bacteria.

Synthesis and Antimicrobial Activity of 4-Oxo-Thiazolidines and 5-Arylidene Derivatives of 2-Amino-5-Ethyl-1,3,4-Thiadiazole

A new series of 5-benzylidene-3-(5-ethyl-[1,3,4]thiadiazol-2-yl)-2-phenyl-thiazolidin-4-ones (3a-3m) were synthesized. The reaction of thioglycolic acid with benzylidene-(5-ethyl-[1,3,4] thiadiazol-2-yl)-amine 1a in the presence of anhydrous ZnCl2 afforded the new heterocyclic compounds 5-benzylidene-3-(5-ethyl-[1,3,4] thiadiazole-yl)-2-phenyl-thiazolidin-4-one, 2a. The latter product on treatment with several selected substituted aromatic aldehydes in the presence of sodium ethoxide underwent the Knoevenagel reaction to yield 5-benzylidene-3-(5-ethyl-[1,3,4] thiadiazol-2-yl)-2-phenyl-thiazolidin-4-ones, 3a-3m. The structures of the compounds were confirmed by IR, 1H-NMR, 13C-NMR and mass spectroscopy and by chemical analysis. All the above compounds were screened for their antimicrobial activity against some selected bacteria and fungi such as E. coli, B. Subtilis, and S. Typhi bacteria and A.niger, A. Flavus and F. oxisporium Fungi. Journal of Bangladesh Academy of Sciences, Vol. 42, No. 2, 155-170, 2018

Homo- and Heteroleptic 8-Quinaldinolate Complexes From Elevated-temperature Rearrangements

Three new zinc 8-quinaldinolate complexes have been obtained from rearrangement reactions at elevated temperatures including the first homoleptic zinc 8-quinaldinolate complex. The homoleptic, trinuclear complex [Zn3(MQ)6] (1) (MQ = 8-quinaldinolate) was obtained by the recrystallisation of amorphous Zn(MQ)2 from a 1,2,4,5-tetramethylbenzene flux at 270°C. The heteroleptic complexes [Zn4Cl4(MQ)4] (2) and [Zn4Cl2(MQ)6] (3) were simultaneously obtained by the reaction between Zn(MQ)2 and anhydrous ZnCl2 under the same conditions. All complexes contain quinaldinolate ligands in a mixed chelating–bridging coordination mode. The homoleptic complex adopts a V-shaped geometry whereas the heteroleptic complexes adopt closely related cyclic structures.

Synthesis and biological activity of 4-thiazolidinone derivatives of phenothiazine

A new series of N-[3-(10H-phenothiazinyl)-propyl]-2-(substituted phenyl)-4-oxo-5-( substituted benzylidene)-1,3-thiazolidine-carboxamide, 5(as) have been synthesized. The cycloaddition reaction of thioglycolic acid with N-[3-(10H-phenothiazinyl)-propyl]-N?-[(substituted phenyl)-methylidene]- urea, 3(a-s) in the presence of anhydrous ZnCl2 afforded new heterocyclic compounds N-[3-(10H-phenothiazinyl)-propyl]-2-(substituted phenyl)-4-oxo- 1,3-thiazolidine-carboxamide, 4(a-s). The later product on treatment with several selected substituted aromatic aldehydes in the presence of C2H5ONa undergoes Knoevenagel reaction to yield 5(a-s). The structure of compounds 1, 2, 3(a-s), 4(a-s) and 5(a-s) were confirmed by IR, 1H NMR, 13C NMR, Fmass and chemical analysis. All above compounds were screened for their antimicrobial activity against some selected bacteria and fungi and for antituberculosis activity compounds have been screened against the bacterium M. tuberculosis.