Mohamed H. Helal

Synthesis and biological evaluation of some novel thiazole compounds as potential anti-inflammatory agents

In the present investigation, furo[2,3-d]thiazol-5(2H)-one 5 was obtained from reaction of thiosemicarbazone derivative 2 with diethyl acetylene dicarboxylate. A series of newly synthesized 2-(hydrazinyl)thiazol-4(5H)-one 6, 7 &8 and 2-(4-(substituted)-thiazol-2-yl)hydrazono derivatives 9a, b &10 were synthesized from treatment of thiosemicarbazone derivative 2 with appropriate α-halogenated compounds. Also, a one pot synthesis of thiazole derivatives 13 &15 was achieved from three components reaction of hydrazone derivative 11 with phenyl isothiocyanate and α-halogenated compounds catalyzed by DMF/KOH. 4-(4-Morpholino phenyl) thiazol-2-amino 17 was obtained via the reaction of acetophenone derivative 1 with thiourea in presence of iodine. The reactivity of 2-aminothiazole 17 toward some electrophilic reagents was investigated. The structure of the newly compounds was confirmed on the basis of elemental analysis and spectral data. The antibacterial activity towards two Gram negative (Proteus mirabilis &Serratia marcesens) and two Gram positive (Staphylococcus aureus &Bacillus cereus) bacteria was investigated. The anti-inflammatory activity was also investigated and the inhibition of the carrageenin-induced oedema by these compounds was established.

Synthesis and characterization of new types of 2-(6-methoxy-2- naphthyl)propionamide derivatives as potential antibacterial and antifungal agents

A series of novel 2-(6-methoxy-2-naphthyl)propionamide derivatives have been efficiently synthesized in excellent yields via the reaction of naproxenoyl chloride with different amino compounds. Most of the synthesized compounds were screened in vitro for their antibacterial and antifungal activities. Most of the compounds showed significant antibacterial and antifungal activities, reaching, in certain cases, the same level of antimicrobial activity as the standard antibacterial agent Ampicilline and antifungal agent Flucanazole. N-(4-(N-arylsulfamoyl)phenyl)-2-(6-methoxynaphthalen-2-yl)propanamide (4a–c), 4-(4-fluorobenzylidene)-2-(1-(6-methoxynaphthalen-2-yl)ethyl)oxazol-5(4H)-one (10b), 2-(6-methoxynaphthalen-2-yl)-N-((5-thioxo-4,5-dihydro-1H-1,2,4-triazol-3-yl)methyl)propanamide (12), and N-((4-amino-5-thioxo-4,5-dihydro-1H-1,2,4-triazol-3-yl)methyl)-2-(6-methoxynaphthalen-2-yl)propanamide (13) were found to be the most potent compounds against most of the tested strains. The antimicrobial activity was further supported by using MIC technique. Structure activity relationship studies revealed several matching pairs.

STUDIES ON THIAZOLOPYRIDINES. PART 5: SYNTHESIS OF HITHERTO UNKNOWN THIAZOLINONE AND THIAZOLO[3,2-a]PYRIDINE DERIVATIVES HAVING IN THEIR STRUCTURE THE MORPHOLIN-4-YL MOIETY

Condensation of thiazolinone 1 with benzaldehydes 2a, b in ethanolic piperidine afforded the methylidene derivatives 3a, b. Cyclocondensation of compound 3b with malononitrile furnished the novel thiazolo[3,2-a]-pyridine 5. Also, compound 3b was condensed with dimethylformamide-dimethylacetal (DMF-DMA) and triethylortho-formate to yield N,N-dimethylamino 6 and ethoxymethylene 7 derivatives respectively. The novel thiazolo[3,2-a]pyridines 10a, b were obtained by cyclocondensation of compounds 3a, b with benzylidene-malononitriles 8a, b. Similarly, cyclocondensation of compound 3b with benzylidenemalononitrile 11 afforded the thiazolopyridines 12a–c. Ternary condensation of compound (12), 4-morpholinobenzaldehyde 2b and malononitrile (1:1:1 molar ratio) produced the thiazolopyridines 14a–c. When compound 10b was subjected to react with malononitrile in dioxane/piperidine under reflux the novel condensed heterocyclic system 18 was obtained. Treatment of ortho-aminocarbonitrile 10b with formic acid, aromatic aldehyde and triethylorthoformate furnished the thiazolo[2′,3′:1,6] pyrido[2,3-d] pyrimidine 20, azomethine 21a, b and ethoxymethylene 22 derivatives respectively. The structure of the synthesized compounds was established by analytical and spectral data.

Studies on Thiazolopyridines. Part 4: Synthesis of Hitherto Unknown 1,4-Bis(thiazolopyridine)benzene Derivatives

2-Cyanomethyl-4-thiazolinone ( 1 ) was condensed with terephthalaldehyde ( 2 ) (2:1 molar ratio) and produced 1,4-bis(2-cyanomethyl-4,5-dihydro-5-methylidene-4-thiazolinone-5-yl) benzene ( 3 ). Treatment of compound ( 3 ) with benzylidenemalononitrile ( 4 ) (1:2 molar ratio) furnished the novel bisthiazolopyridines ( 6a-e ). Condensation of compound ( 1 ) with aromatic aldehyde yielded the benzylidene derivatives ( 7a-f ), which on treatment with compound ( 8 ) (2:1 molar ratio) afforded the novel bisthiazolopyridines ( 10a-f ). Structures of the synthesized compounds have been established by elemental analyses and spectral data.

One-step synthesis of chromene-3-carboxamide, bis-chromene, chromeno[3,4-c]pyridine and bischromeno[3,4-c]pyridine derivatives for antimicrobial evaluation

Cyanoacetamide derivatives were reacted with salicylaldehyde under different conditions afforded chromenes and coumarin derivatives respectively. A number of chromeno[3,4-c]pyridine derivatives were prepared from the reaction of N-cyclohexyl-2-imino-2H-chromene-3-carboxamide with malononitrile and/or cynaothiocatemaide. Bischromeno[3,4-c]pyridine derivatives were prepared from the reaction of N,N’-(ethane-1,2-diyl)bis(2-imino-2H-chromene-3-carboxamide) with malononitrile and/or N-alkyl-2-cyanoacetamide derivative with 2-iminochroemen derivative, respectively. Some of these compounds were screened for their antimicrobial activities.

Design, synthesis, characterization, quantum-chemical calculations and anti-inflammatory activity of novel series of thiophene derivatives.

Interaction of 1-(4-morpholinophenyl)ethanone 1 with either malononitrile or ethyl cyanoacetate 2 afforded Knoevenagel-Cope product 3. In subsequent treatment of 3 with sulfur, the 2-aminothiophene derivatives (4a, 4b) are formed under basic conditions. The solvent-free reaction of thiophene derivative 4a with ethyl cyanoacetate afforded thieno[2,3-d][1,3]oxazine derivative 6. The base catalyzed condensation of 2-aminothiophene derivative (4a) with ethyl cyanoacetate afforded N-(thieno-2-yl) cyanoacetamide derivative 7. The latter was used to synthesize different heterocyclic derivatives comprising, pyridine and coumarin rings. Also, several substituted thieno[2,3-d]pyrimidines have been prepared from reaction of 2-aminothiophene-3-carbonitrile 4b with some electrophilic reagents. The structure of the newly compounds were confirmed on the basis of elemental analysis and spectral data. The molecular modeling of the synthesized compounds has been drawn and their molecular parameters were calculated. Also, valuable information is obtained from calculation of the molecular parameters including electronegativity, net dipole moment of the compounds, total energy, electronic energy, binding energy, HOMO and LUMO energy. Evaluation of anti-inflammatory activity of the tested compounds was performed in albino rats by producing carrageenan induced paw oedema and measuring the zone of inflammation at different time intervals i.e. 1, 2, 3 and 4h after carrageenan injection. Results indicated that most of the tested compounds showed moderate to good activity comparable to indomethacin. Also, compound 16 with additional morpholine ring beside the thiophene ring inhibits carrageenan induced paw oedema more than the standard indomethacin drug at all the time scales studied. Thus, compound 16 is considered as a promising compound for further modification to obtain clinically useful anti-inflammatory agent.

Synthesis, characterisation and antimicrobial activity of thiazole, bisthiazole, pyridone and bispyridone derivatives

N-cyclohexyl-2-cyanoacetamide was reacted with phenyl isothiocyanates and sulfur to give thiazolidine and bisthiazolidine derivatives. Treatment of N-cyclohexyl-2-cyanoacetamide with phenyl isothiocyanate and KOH followed by in situ heterocyclisation with α-halo compounds gave thiazole derivatives. Treatment of N-cyclohexyl-2-cyanoacetamides with cinnamonitriles gave pyridone and bispyridone derivatives. N-cyclohexyl-2-cyanoacetamide coupled smoothly with benzene-diazonium chloride in pyridine. Cyclocondensation of N-cyclohexyl-2-cyanoacetamide with acetylacetone gave 1,1′-(ethane-1,2-diyl)bis(4,6-dimethyl-2-oxo-1,2-dihydropyridine-3-carbonitrile). Ternary condensation of N-cyclohexyl-2-cyanoacetamide, malononitrile and acetaldehyde gave a bispyridone derivative. Some of the new compounds were tested against bacteria and some fungi.

Synthesis, Characterization, and Antioxidant and Bleomycin-Dependent DNA Damage Evaluation of Curcumin Analogs

In an attempt to find a new class of antioxidant agents, a series of pyrazole, pyridopyrazoltriazine, pyrazolotriazine, isoxazole, and pyridine‐containing products were prepared, starting with curcumin and appropriate chemical reagents. Thus, curcumin 1 undergoes coupling reaction with diazonium salts 2–5 to afford the corresponding 4‐arylazo derivatives 6–9. Heating of 6 and/or 7 in acetic acid furnished the corresponding pyrazolotriazines 10 and 11. Also, pyrazole and isoxazole derivatives were obtained upon treatment of 10 with hydrazines or hydroxylamine hydrochloride. Furthermore, multicomponent reaction of 10 with malononitrile/CH3COONH4 or phenacylpyridinium iodide/CH3COONH4 produced the corresponding bispyridines 16 and 17, respectively. Furthermore, condensation of 10 with guanidine nitrate or thiourea gave the corresponding pyrimidines 18 and 19, respectively. Finally, other curcumin derivatives were obtained on condensation of 1 with isatins and pyrazole‐4‐aldehyde. The newly synthesized compounds were evaluated as antioxidant agents. The results showed clearly that most of the compounds exhibited good activities, except for compounds 9 and 12. Compounds 1, 3, 15, and 23 exhibited high protection against DNA damage induced by the bleomycine–iron complex.

Novel Synthesis of Pyrano[2,3-d]Thiazole, Thiazolo[3,2-a]Pyridine, and Pyrazolo [3′,4′:4,5] Thiazolo[3,2-a]Pyridine Derivatives

Cyclocondensation of 2-cyanomethyl-4-thiazolidinone (1) with tetracyanoethylene (2) furnished pyrano[2,3-d]thiazole derivative (4) . Benzo[e]pyrano[2,3-d]thiazole derivative (6) was obtained by cyclization of compound (1) with salicylaldehyde. In a similar manner, condensation of compound (1) with 2-hydroxy-1-naphthaldehyde in refluxing ethanol yielded naphtho[e]pyrano[2,3-d]thiazole derivative (7) . Interaction of compound (9) with benzylidenemalononitriles (10) (1 : 1 molar ratio) at reflux temperature in ethanol in the presence of piperidine afforded thiazolo[3,2-a]pyridines (12a-c) . Treatment of compound (12a) with hydrazines furnished pyrazolo[3′,4′:4,5] thiazolo[3,2-a]pyridines (14a,b) . The reaction of compound (1) with benzyli-denecyanoacetate (16) yielded 5-hydroxythiazolo[3,2-a]pyridine derivative (21) . Cyclization of bis(thiazolinone) (23) with benzylidenemalononitriles (10) produced bis(thiazolopyridine) derivatives (25a,b) .

An overview on synthetic strategies to coumarins

ABSTRACT Coumarins units have recently emerged as a hot topic of research due to their diverse applications. Their synthesis is partly based on classical methodologies such as Pechmann reaction or Knoevenagel condensation, but it also sparked the discovery of completely new pathways. In very recent years so-called vertically expanded coumarins were synthesized, effectively expanding the portfolio of existing architectures. This review serves as a guide through synthesis strategies to coumarins. GRAPHICAL ABSTRACT