Stereoselective intramolecular cycloadditions of homochiral N-alkenoyl aryl azides

Starting from the commercially available (S)-1-phenylethylamine and l-alanine benzylester, we synthesised the homochiral N-alkenoyl aryl azides 2a–2d. The intramolecular cycloaddition of unsubstituted 2a and 2b gave enantiopure 3,3a-dihydro-1,2,3-triazolo[1,5-a][1,4]benzodiazepine-4(6H)-ones 3a, 3b, 4a and 4b, while phenyl-substituted 2c and 2d gave enantiopure 1,1a-dihydro-2H-azirino[2,1-c][1,4]benzodiazepine-4(6H)-ones 5c, 5d, 6c and 6d.     

Synthesis of some new 4-oxo-thiazolidines,tetrazole and triazole derived from 2-SH-benzothiazole and antimicrobial screening of some synthesized

A new heterocyclic derivative of 2-mercaptobenzothiazole (MBT) comprising 4-oxothiazolidines, tetrazole and triazole, through the reaction of (MBT) with hydrazine hydrate obtained 2-hydrazobenothiazol (1), which was condensed with various aromatic aldehydes. Azomethine derivatives (2a–c) are converted into a number of 4-oxothiazolidines (3a–c) and tetrazole derivatives (4a–c), through the reaction of azomethine derivatives (2a–c) with mercaptoacetic acid and sodium azide, respectively. Also the reaction of compound (1) with triethylorthoformate and nitrous acid to produce the corresponding (triazole and tetrazole) benzothiazole (5,6) was reported.Triazole moieties reported condensation (MBT) with ethylbromo acetate and potassium hydroxide by the fusion method and resulted in ester-2-mercaptobenzothiazole (7), which was treated with hydrazine hydrate to give a hydrazine derivative (8), then converting these compounds (8) to phenyl semicarbazide (9) and phenyl thiosemicarbazide (10) derivatives. Cyclization compounds (9,10) in alkaline media (4 N·NaOH) gave triazoles compounds (11,12). Furthermore the compound (8) was converted to the dithiocarbazate salt (13) which was then cyclized with hydrazine hydrate to give substituted triazole (14). The prepared compounds were identified by spectral methods (FTIR, ¹H NMR, ¹³C NMR) and some of its physical properties were measured and furthermore the effects of the preparing compounds on some strains of bacteria were studied.     

Synthesis and in vitro cytotoxic evaluation of some novel hexahydroquinoline derivatives containing benzofuran moiety

A series of new ethyl 4-(2-(benzofuran-2-yl)-4-substituted-1,4,5,6,7,8-hexahydroquinolin-1-yl)-benzoate 3a–c was synthesized by Michael condensation of benzofuran chalcones 1a–c and cyclohexanone to give 2-(2-benzofuranyl)-4-substituted-5,6,7,8-tetrahydro-4-H -chromene 2a–c, followed by reaction of the latter with ethyl 4-aminobenzoate. Condensation of 3a–c with different amines afforded the corresponding amides 4a–e. On the other hand, upon treatment compounds 3a–c with hydrazine hydrate gave the benzohydrazide derivatives 5a–c. The reaction of compounds 5a–c with different thio/isocyanate gave the corresponding thiosemicarbazide and semicarbazide derivatives 6a–c. Meanwhile compounds 5a–c were reacted with ethyl cyanoacetate and different β-dicarbonyl compounds such as acetyl acetone, ethyl acetoacetate, and diethyl malonate to afford pyrazolyl derivatives 7a, b; 8a, b; 9a, b; and 10a–c, respectively. Moreover, 5a–c were reacted with carbon disulfide to synthesize the corresponding oxadiazolyl derivatives 11a–c, while their condensation with different aromatic aldehydes gave the corresponding Schiff bases 12a–d. Cytotoxic evaluation of some of the newly synthesized compounds against human hepatocellular carcinoma cell lines (HepG-2) revealed that the tested compounds produce promising inhibitory effect against the growth of HepG-2 cells with IC₅₀ values ranged from 11.9 to 19.3 µg/mL.     

The reaction of 2-(1-hydropolyfluoro-1-alkenyl)-4H-3,1-benzoxin-4-ones with dinucleophilic reagents: a convenient route to fluoroalkylated nitrogen-containing tricyclic compounds

The reactions of 2-(1-hydropolyfluoro-1-alkenyl)-4H-3,1-benzoxin-4-ones (2) with hydrazine hydrate and phenyl hydrazine were investigated. The reaction of 2 with hydrazine hydrate in ethanol under reflux condition readily gave 2-fluoroalkyl-4H-pyrazolo[5,1-b]quinazolin-9-ones (3) in high yields. The reaction of 2 with phenyl hydrazine, however, resulted in the formation of 2-(2-phenyl-5-fluoroalkyl-2H-pyrazol-3-yl) benzoic acids (7). Further treatment of 7 with PPA gave 1-phenyl-4,9-dihydro-3-fluoroalkyl-1H-pyrozolo[3,4-b]quinolin-4-ones (4) in 65-80% overall yields.     

Microwave assisted synthesis of 2,3-dihydro-4H-benzo[4,5]thiazolo[3,2-a]furo[2,3-d]pyrimidin-4-ones and 6,7-dihydro-5H-furo[2,3-d]thiazolo[3,2-a]pyrimidin-5-ones using Mn(OAc)3

2-Hydroxy-4H-benzo[4,5]thiazolo[3,2-a]pyrimidin-4-one 2a and 7-hydroxy-5H-thiazolo[3,2-a]pyrimidin-5-one 2b, were obtained in high yields under mild conditions from the cyclization reactions of bis-(2,4,6-trichlorophenyl) malonate and 2-aminobenzothiazole or 2-aminothiazole, respectively. A new class of compounds, 2,3-dihydro-4H-benzo[4,5]thiazolo[3,2-a]furo[2,3-d]pyrimidin-4-ones and 6,7-dihydro-5H-furo[2,3-d]thiazolo[3,2-a]pyrimidin-5-ones, were synthesized via the microwave assisted radical addition of compounds 2a and 2b to various alkenes using manganese(III) acetate. A preliminary acetylcholine esterase (AchE) inhibition test of compound 4e showed excellent (92%) inhibitory potential, comparable with the standard drug Donapezil®.     

Synthesis and rearrangement of cycloalkyl[1,2-e]oxazolo[3,2-a]pyrimidin-8/9-ones: an access to cycloalkyl[1,2-d]oxazolo[3,2-a]pyrimidin-5-ones

2-Substituted-4a-hydroxy-9H-cycloalkyl[1,2-e]oxazolo[3,2-a]pyrimidin-9-ones 2a-c were synthesized by an one-step cyclocondensation from the 5-substituted-2-amino-2-oxazolines 1a-c with ethyl 2-oxocyclohexanecarboxylate in ethanol at room temperature, and easily dehydrated to provide 2-substituted-9H-cycloalkyl[1,2-e]oxazolo[3,2-a]pyrimidin-9-ones 3. In refluxing xylene, the reaction conducted with various ethyl 2-oxocycloalkanecarboxylates led to the two isomeric 2-substituted-8/9H-cycloalkyl[1,2-e]oxazolo[3,2-a]pyrimidin-8/9-ones 3 and 2-substituted-5H-cycloalkyl[1,2-d]oxazolo[3,2-a]pyrimidin-5-ones 4. The structure of some compounds was unambiguously established using X-ray crystallography. According to results from the DSC analysis of compound 2a, formation of the thermodynamically stable pyrimidinones 4 could be related to an intramolecular rearrangement of kinetically controlled pyrimidinones 3.     

Synthesis of pyrazolo[4,3-e][1,2,4]triazolo[4,3-c]pyrimidines

Starting from 1,5-dihydro-4H-pyrazolo[3,4-d]pyrimidin-4-ones, a synthesis pathway to the tricyclic pyrazolo[4,3-e][1,2,4]triazolo[4,3-c]pyrimidines is described. Reaction of 1,5-dihydro-4H-pyrazolo[3,4-d] pyrimidin-4-ones with phosphoryl chloride afforded the corresponding 4-chloro-1H-pyrazolo[3,4-d]pyrimidines. Treatment of these compounds with hydrazine hydrate at reflux temperature gave the hydrazino derivatives, which were subsequently cyclized to the titled compounds on heating with orthoesters in ethanol.     

Synthesen von basisch substituierten ([1]Benzo-)Thieno-[2,3—d]pyrimidin-Derivaten und von ([1]Benzo-)Thieno-[2,3-d]-1,2,4-triazolo[4,3-a]pyrimidin-Derivaten

Reaction of 2-methylthio-thieno[2.3-d]pyrimidin-4(3H)-ones with heterocyclic secondary amines, ethanolamine and hydrazine, resp., gave the corresponding derivatives with a basic substituent in position 2. Cyclization of the hydrazino compounds with formic acid gave derivatives of thieno[2.3-d]-1.2.4-triazolo[4.3-a]pyrimidine and [1]benzothieno[2.3-d]-1.2.4-triazolo[4.3-a]pyrimidine, two new heterocyclic systems.     

The Synthesis of Some Pyrazolyl- and Thiazolylthienopyridines

2-acetyl-3-amino-4,6-dimethylthieno[2,3-b]pyridine 1 reacted with dimethoxy-tetrahydrofuran in acetic acid and ethyl cyanoacetate in the presence of ammonium acetate or with NaNO₂ in the presence of an AcOH/HCl mixture to produce 2–4. Compound 2 reacted with aromatic aldehydes, semicarbazide hydrochloride, thiosemicarbazide, and phenyl hydrazine or with hydrazine hydrate to give compounds 5a–c and 11a–d, respectively.

Chalcone 5 reacted with hydrazines, hydroxylamine hydrochloride, or thiourea to produce compounds 6–9. Thiosemicarbazone 11b reacted with α -haloester to produce the corresponding thiazolidinone derivatives 12a, b ; also it reacted with ω -bromoacetophenone to give thiazoline derivatives 13a, b .     

Synthesis,anti-inflammatory,analgesic and anticonvulsant activities of some new 4,6-dimethoxy-5-(heterocycles)benzofuran starting from naturally occurring visnagin

Novel 3-(4,6-dimethoxybenzofuran-5-yl)-1-phenyl-1H-pyrazole-4-carboxaldehyde (3) and 3-chloro-3-(4,6-dimethoxybenzofuran-5-yl)propenal (4) were prepared via Vilsmeier–Haack reaction of 1-(4,6-dimethoxybenzofuran-5-yl)ethanone (1) and its hydrazone derivative 2. Reaction of compound 4 with some hydrazine derivatives, namely hydrazine hydrate, phenylhydrazine and benzylhydrazine hydrochloride led to the formation of pyrazole derivatives 5–8, respectively. On the other hand, reaction of compound 4 with thiourea, urea or guanidine gave the pyrimidine derivatives 9–11, respectively. Reaction of amino compound 11 with acetic anhydride, benzoyl chloride and benzenesulphonyl chloride yielded N-substituted pyrimidine derivatives 12–14, respectively. Reaction of diazonium salt of compound 11 with sodium azide afforded azidopyrimidine derivative 15, which upon reaction with ethyl acetoacetate gave 1,2,3-triazole derivative 16. Acid catalyzed reaction of 11 with p-nitrobenzaldehyde gave Schiff base 17, which cyclized upon reaction with thioglycolic acid or chloroacetyl chloride to give thiazolidin-4-one 18 and azetidin-2-one 19, respectively. The newly synthesized compounds were tested for their anti-inflammatory, analgesic and anticonvulsant activities. Depending on the obtained results, the newly synthesized compounds possess significant anti-inflammatory, analgesic and anticonvulsant activities.     

Synthesis of some novel pyrazolo[1,5-a]quinazolines and their fused derivatives

New pyrazolo[1,5-a]quinazoline-3-carbonitriles 4a,b were obtained via cyclocondensation of 5-amino-3-cyanomethyl-1H-pyrazole-4-carbonitrile (1) with enaminones of 1,3-cyclohexanedione derivatives 2a,b in refluxing glacial acetic acid. Condensation of compounds 4a,b with various aromatic aldehydes furnished the corresponding arylidene derivatives 6a–j. On the other hand, condensation of 4a,b with o-hydroxybenzaldehydes yielded the polyheterocyclic compounds 10a–h. Coupling of compounds 4a,b with aryldiazonium chlorides led to formation of 2-arylhydrazono derivatives 12a–h. Also, reaction of compounds 4a,b with phenyl isothiocyanate, followed by addition of ethyl chloroacetate and chloroacetonitrile, afforded the polyheterocyclic compounds based on pyrazolo[1,5-a]quinazoline core. The reaction of compounds 4a,b with phenyl isothiocyanate and elemental sulfur gave the thiazole-2-thione derivatives 25a,b. The reaction of enamines of compounds 4a,b with each of hydrazine hydrate and guanidine hydrochloride afforded pyrazolo[4″,3″:5′,6′]pyrido[4′,3′:3,4]pyrazolo[1,5-a]quinazolin-8-ones 30a,b and pyrimido[5″,4″:5′,6′]pyrido[4′,3′:3,4]pyrazolo[1,5-a]quinazolin-9(10H)-ones 33a,b, respectively. The structures of all the newly synthesized compounds were elucidated by elemental analyses and spectral data. The plausible mechanisms have been postulated to account for their formation.     

Synthesis and antimicrobial activity of Schiff bases and 2-azetidinones derived from quinazolin-4(3H)-one

A series of 2-oxo-azetidinyl-quinazolin-4(3H)-ones 5a–k have been synthesized from Schiff bases 4a–k. Schiff bases were synthesized by the condensation reaction of compound 3 with substituted aromatic aldehydes. The benzoxazinone 2 was prepared by the cyclization reaction of acid chloride 1 with 5-bromo anthranilic acid. Further reaction of benzoxazinone 2 with hydrazine hydrate yielded compound 3. The structures of the synthesized compounds were elucidated on the basis of elemental analyses as well as IR and NMR spectral data. Schiff bases 4a–k and 2-azetidinones 5a–k were screened for antibacterial and antifungal activities in vitro. Compounds having chloro and methoxy groups exhibited good antimicrobial activity.     

Novel thiosemicarbazone derivatives containing benzimidazole moiety: Green synthesis and anti-malarial activity

A series of (E)-2-[5-chloro-1-(1H-benzo[d]imidazol-2-yl)ethylidene] N-(substituted) hydrazine carbothioamide (7a–7t) and (E)-2-[1-(1H-benzo[d]imidazol-2-yl)ethylidene] N-(substituted) hydrazine carbothioamide (8a–8t) were prepared via the synthesis of 1-(substituted-1H-benzimidazol-2-yl) ethanol (3a–3b) which was synthesized by the condensation of substituted o-phenylenediamine (2a–2b) with dl-lactic acid (1) followed by oxidation with sodium hypochlorite in mild acidic condition to form the corresponding ketones 4a–4b. Final compounds were formed by condensation of 4a–4b with different thiosemicarbazides 6a–6t. A total of 40 compounds were synthesized and characterized by FT-IR, ¹H NMR, ¹³C NMR, Mass spectral technique and elemental analysis, in addition they were evaluated for anti-malarial properties. Among the compounds tested 7o, 7p, 7q, 7r, 7s, 8e and 8h exhibited good antimalarial activity in vitro.     

Novel pyrimidine and its triazole fused derivatives: Synthesis and investigation of antioxidant and anti-inflammatory activity

In the present study, we have carried out the synthesis of novel dihydropyrimidinecarbonitrile (1a–c), its dimethylated adduct (2a–c), and hydrazine derivative (3a–c) of 2a–c and its triazole fused derivatives (4a–c, 5a–c and 6a–c). The structure of newly synthesized compounds was confirmed by IR, ¹H NMR, mass spectral data and elemental analysis. Further the novel derivatives were investigated for their in vitro antioxidant and anti-inflammatory activity. The results revealed that some of the tested compounds showed potent antioxidant and anti-inflammatory activity. The mass spectral pattern of 6a has been investigated in order to elucidate the structure.     

Synthesis of some fused heterocyclic systems and their nucleoside candidates

A series of pyridofuro compounds were synthesized from 4-(4-chlorophenyl)-1,2-dihydro-2-oxo-6-(thiophen-2-yl)pyridine-3-carbonitrile (1) as starting material. Alkylation of 1 with ethyl bromoacetate gave the corresponding ester 2, which was condensed with hydrazine hydrate to afford the corresponding acid hydrazide derivative 3. Thrope-Ziegler cyclization of 2 with sodium methoxide gave furo[2,3-b]pyridine derivative 4, which was reacted with thiosemicarbazide, allyl isothiocyanate, formamide or hydrazine hydrate to give furopyridine derivatives 5–8, respectively. The latter compound 8 was cyclized with acetylacetone or formic acid to give the corresponding compounds 9 and 10, respectively. Furthermore, sulfurization of 1 with P₂S₅ gave the corresponding thioxopyridine 11, which was reacted with glycosyl (or galactosyl) bromide, morpholine or piperidine to give the corresponding thioglycoside 12a,b and Mannich base 14a,b derivatives. The deacetylation of 12a,b gave the corresponding deacetylated thioglycosides 13a,b, respectively. All the newly synthesized compounds were characterized by the elemental analyses and spectroscopic evidences (IR, ¹H- and ¹³C NMR).     

Synthesis of pyrazolo[4,3-<Emphasis Type="Italic">e</Emphasis>][1,2,4]triazolo[4,3-<Emphasis Type="Italic">c</Emphasis>]pyrimidines

Starting from 1,5-dihydro-4H-pyrazolo[3,4-d]pyrimidin-4-ones, a synthesis pathway to the tricyclic pyrazolo[4,3-e][1,2,4]triazolo[4,3-c]pyrimidines is described. Reaction of 1,5-dihydro-4H-pyrazolo[3,4-d] pyrimidin-4-ones with phosphoryl chloride afforded the corresponding 4-chloro-1H-pyrazolo[3,4-d]pyrimidines. Treatment of these compounds with hydrazine hydrate at reflux temperature gave the hydrazino derivatives, which were subsequently cyclized to the titled compounds on heating with orthoesters in ethanol. Correspondence: Abolghasem Davoodnia, Department of Chemistry, School of Sciences, Islamic Azad University, Mashhad Branch, Mashhad 91735-413, Iran.     

Synthesis,antibacterial activity,and fluorescence properties of a novel series from [2,4-dioxochromen-3(4<Emphasis Type="Italic">H</Emphasis>)methyl]amino acid

A new solvent-free method for synthesis of starting compounds 2,4-dioxochromen-3(4H)methyl amino acetic acid derivatives 1a–e via a green approach is reported. Also, the behavior of compound 1a towards various nitrogen nucleophiles such as primary amines, hydrazine hydrate, and hydroxylamine hydrochloride to give corresponding compounds 2–4 was studied. Furthermore, chlorination of compound 1a using a mixture of PCl₅/POCl₃ to yield acid chloride derivative 5 and the reaction of the latter compound 5 with various amino acids to obtain dipeptide compounds 6a–e are described. Moreover, cyclization of compound 1a in alkaline medium to afford dihydrochromeno[3,4-c]pyrrole-1-carboxylic acid 7 and cyclization of 6b in acidic medium, namely Ac₂O, to yield piperazine derivative 8 are reported. Also, reaction of compound 1a with maleic anhydride in dioxane to afford Diels–Alder adduct 9, which posteriorly reacted with hydrazine hydrate to give 10, was investigated. Most of the newly synthesized compounds were screened against Gram-positive and Gram-negative bacteria, with compound 5 exhibiting the maximum inhibition zone towards all four types of bacteria. In addition, the absorption and fluorescence emission of some of the substituted coumarins were studied in dioxane, revealing that the substituents altered both the absorption and fluorescence emission maxima.     

An efficient substituent dependent synthesis of congested pyridines and pyrimidines

An efficient and versatile synthesis of various congested pyridines 3a-h, 6a,b, 8a-n, 10a-g, and 16a,b, and (pyrimidin-4-yl)acetonitriles 13a-g has been delineated by base catalyzed ring transformation of suitably functionalized 2H-pyran-2-ones 1a-h, 5, 7, and 15 by formamidine acetate 2a, acetamidine hydrochloride 2b, S-methylisothiourea 9a, pyrazol-1-yl-carboxamidine 9b, and arylamidine hydrochloride 12 separately in the presence of powdered KOH in dry DMF.     

A facile route to phenyl, phenylsulfanyl and phenylselanyl substituted pyrano[3,2-c]chromenes

The synthesis of phenyl, phenylsulfanyl and phenylselanyl substituted pyrano[3,2-c]chromenes 4 is accomplished via cyclocondensation of 4-oxo-4H-chromen-3-carbaldehydes 1 with appropriately substituted acetic acids 2 under mild conditions. Further treatment of 4 with alcohol or water led to 5-alkoxy- and 5-hydroxy-2H,5H-pyrano[3,2-c]chromen-2-ones 5 and 6, respectively. Acid and thermal catalysed rearrangement of 4-6 gave 5-hydroxypyrano[2,3-b]chromen-2(10aH)-ones 7 and their subsequent substitution led to 5-alkoxyderivatives 8. Reaction of 4 with amides led to 5-acylamino or 5-phenylsulfonamino substituted 2H,5H-pyrano[3,2-c]chromen-2-ones 9. Reactions were performed under heating or microwave irradiation.     

Design and synthesis of some novel pyridothienopyrimidine derivatives and their biological evaluation as antimicrobial and anticancer agents targeting EGFR enzyme

A new series of pyridothienopyrimidine derivatives was designed and evaluated as antimicrobial and anticancer agents. The target compounds were synthesized starting with 3-aminothieno[2,3-b]pyridine-2-carboxamide derivative 1 which underwent cyclocondensation reaction with aromatic aldehydes to give the key intermediates 2a,b. By further treatment of 2a,b with various reagents, the target 2,4-disubstituted-pyrido[3′,2′:4,5]thieno[2,3-d]pyrimidines 3a,b–11a,b were obtained. To evaluate the antimicrobial activity of the new compounds, they were tested against five bacterial and five fungal strains. Compounds 6c, 8b, 9a and 9b revealed the most significant antimicrobial activity against the tested microorganisms with MIC values range (4–16 μg/mL). Also, compounds 2a,b–11a,b were screened for their in vitro cytotoxic activity against HepG-2 and MCF-7 cancer cell lines compared with doxorubicin and cisplatin as references drugs. Moreover, compounds (2b, 4a, 6a, 7b, 7c and 9a) which exhibited the most potent anticancer activity, were further subjected to EGFR^WT enzyme inhibition assay utilizing erlotinib as a standard drug. The compounds 6a, 7b, 7c and 9a which showed the most promising suppression effects were also evaluated as inhibitors against the mutant forms EGFR^L858R and EGFR^T790M. The 4-aminopyrazolone analogue 9a showed superior anticancer activity against both HepG-2 and MCF-7 cell lines (IC50 = 1.27, 10.80 μM, respectively) and more potent enzymatic inhibition activity against EGFR^WT and its mutant forms EGFR^L858R and EGFR^T790M than that obtained by erlotinib (IC₅₀ = 0.021, 0.053, 0.081 µM, respectively, IC_50erlotinib; 0.027, 0.069, 0.550 µM, respectively). Finally, the molecular docking study showed good binding patterns of the most active compounds with the prospective target EGFR^WT.