Synthesis of new pyrazolo[1,5‐a]pyrimidines and pyrazolo[3,4‐b]pyridines

While 3(5)‐aminopyrazole reacts with enaminonitrile to yield pyrazolo[1,5‐a]pyrimidines, 3‐amino‐5‐pyrazolone reacts with the same reagents to yields pyrazolo[3,4‐b]pyridines.     

Regioselective synthesis of some novel pyrazoles,isoxazoles, pyrazolo[3,4‐d]pyridazines and isoxazolo[3,4‐d]pyridazines pendant to benzimidazole

2‐Acetyl‐1‐methyl‐1H‐benzimidazole reacts with dimethylformamide‐dimethyl‐acetal (DMF‐DMA) to afford the corresponding E‐1‐(1‐methyl‐1H‐benzimidazol‐2‐yl)‐3‐N,N‐dimethylaminoprop‐2‐enone. The latter compound reacts regioselectively with some nitrilimines and nitrile oxides to afford the corresponding pyrazole and isoxazole derivatives, respectively. These reaction products react with hydrazine hydrate to give the novel pyrazolo[3,4‐d]pyridazine and isoxazolo[3,4‐d]pyridazine derivatives, respectively.     

Studies on uracils: A facile one‐pot synthesis of pyrazolo[3,4‐d]pyrimidines

The reaction of 6‐hydrazino uracils 1 and nitrones 2 result in an efficient one‐pot synthesis of pyrazolo[3,4‐d]pyrimidines 3 in excellent yields. The isolation of the by‐product aniline from the reaction mixture supported the plausible mechanism for the formation of pyrazolo[3,4‐d]pyrimidines.     

A new approach for the synthesis of some pyrazolo[5,1‐c]triazines and pyrazolo[1,5‐a]pyrimidines containing naphtofuran moiety

Naphtho[2,1‐b]furan‐2‐yl)(8‐phenylpyrazolo[5,1‐c][1,2,4]triazin‐3‐yl)methanone, ([1,2,4]triazolo[3,4‐c][1,2,4]triazin‐6‐yl)(naphtho[2,1‐b]furan‐2‐yl)methanone, benzo[4,5]imidazo[2,1‐c][1,2,4]triazin‐3‐yl‐naphtho[2,1‐b]furan‐2‐yl‐methanone, 5‐(naphtho[2,1‐b]furan‐2‐yl)pyrazolo[1,5‐a]pyrimidine, 7‐(naphtho[2,1‐b]furan‐2‐yl)‐[1,2,4]triazolo[4,3‐a]pyrimidine, 2‐naphtho[2,1‐b]furan‐2‐yl‐benzo[4,5]imidazo[1,2‐a]pyrimidine, pyridine, and pyrazole derivatives are synthesized from sodium salt of 5‐hydroxy‐1‐naphtho[2,1‐b]furan‐2‐ylpropenone and various reagents. The newly synthesized compounds were elucidated by elemental analysis, spectral data, chemical transformation, and alternative synthetic route whenever possible. J. Heterocyclic Chem., (2012).     

A convenient synthesis of pyrazolo[3,4‐d]pyrimidine‐4,6‐dione and pyrazolo[4,3‐d]pyrimidine‐5,7‐dione derivatives

Pyrazolo‐[3,4‐d]pyrimidine‐4,6‐diones 5 and pyrazolo[4,3‐d]pyrimidine‐5,7‐diones 7 were synthesized by Curtius rearrangement of pyrazolic mono‐esters 2 and 3 followed by hetero‐cyclization via the ureas derivatives 4 and 6 under alkaline conditions.     

Synthesis of some new bipyridines,thieno[2,3‐b]pyridines,and pyrazolo[3,4‐b]pyridines

Cyclocondensation of cyanoacetamide and cyanothioacetamide with sodium salt of 3‐hydroxy‐1‐(pyridin‐3‐yl)prop‐2‐en‐1‐one gave 6‐oxo‐[2,3′]bipyridine 5a and 6‐thioxo‐[2,3′]bipyridine 5b derivatives, respectively. Compound 5b upon treatment with different methylenes 8 gave thieno[2,3‐b]pyridines 10 . Treatment of 5b with iodomethane gave bipyridine derivative 7 , which cyclocondensed with hydrazines 11 to give pyrazolo[3,4‐b]pyridines 13 . J. Heterocyclic Chem., (2012).     

Synthesis of some new pyrido[2,3‐d]pyrimidines and their ribofuranosides as possible antimicrobial agents

The ribofuranosides, namely, 4‐amino‐5,7‐disubstituted‐1‐[2′,3′,5′‐tri‐O‐benzoyl‐α‐d ‐ribofuranosyl]pyrido‐[2,3‐d] pyrimidine‐2(1H)‐thiones, have been synthesized by the condensation of trimethylsilyl derivatives of 5,7‐disubstituted pyrido[2,3‐d]pyrimidine‐2(1H)‐thiones with β‐d ‐ribofuranose‐1‐acetate‐2,3,5‐tribenzoate in the presence of SnCl₄. The heterocyclic bases, namely, 4‐amino‐5,7‐disubstituted pyrido[2,3‐d]pyrimidine‐2(1H)‐thiones, were synthesized by the treatment of 2‐amino‐3‐cyano‐4,6‐disubstituted pyridines with thiourea. The structures of all the synthesized ribofuranosides and their precursors have been established by elemental analysis, IR, and ¹H NMR spectral data. The ¹³C NMR data of ribofuranosides has also been presented. All the synthesized heterocyclic bases and their ribofuranosides have been screened for their antibacterial and antifungal activities. © 2001 John Wiley & Sons, Inc. Heteroatom Chem 12:52–56, 2001     

Design and synthesis of novel sulfone‐containing pyrazolo[1,5‐a]‐pyrimidines and pyrazolo[5,1‐d][1,2,3,5]tetrazine‐4(3H)‐ones

A series of novel sulfone‐containing pyrazolo[1,5‐a]pyrimidines ( 2‐3 ) and pyrazolo[5,1‐d][1,2,3,5]tetra‐zine‐4(3H)‐ones ( 5a‐5k ) were designed and efficiently synthesized, some of which have been identified as being potential rape inhibitors. These results widen the structural diversity of rape inhibitors and confirm the perspectives of further investigations in this area. Moreover, a plausible reaction mechanism is outlined.     

Synthesis and antitumor activity of some new pyrazolo[1,5-a] pyrimidines

New series of pyrazolo[1,5-a]pyrimidine derivatives 7a-i, 11a-c and Schiff bases 13a-c were synthesized and screened for their in vitro antitumor activity against three human carcinoma cell lines, namely colorectal carcinoma (HCT116), prostate adenocarcinoma (PC-3) and liver carcinoma (HepG-2) using MTT cytotoxicity assay at 100 μg/mL. Some of the tested compounds displayed good anticancer activities against HCT-116 and PC-3 cells. Whereas, compounds 7d and 11a showed better antitumor activity than the rest of the compounds against both cell lines. A structure-activity relationship (SAR) has been discussed and structures of the newly synthesized compounds were confirmed by different spectral data (MS, IR, ¹H NMR and ¹³C NMR) and elemental analysis.     

A new nano‐Fe3O4‐supported organocatalyst based on 3,4‐dihydroxypyridine: an efficient heterogeneous nanocatalyst for one‐pot synthesis of pyrazolo[3,4‐b]pyridines and pyrano[2,3‐d]pyrimidines

A simple and practical strategy for the synthesis of a novel nano‐Fe₃O₄‐supported organocatalyst system based on 3,4‐dihydroxypyridine (Fe₃O₄/Py) has been developed. The prepared catalyst was characterized using Fourier transform infrared spectroscopy, transmission and scanning electron microscopies, X‐ray diffraction, vibrating sample magnetometry and energy‐dispersive X‐ray analysis. Accordingly, the Fe₃O₄/Py nanoparticles show a superparamagnetic property with a saturation magnetization of 61 emu g^?1, indicating potential application in magnetic separation technology. Our experimental results reveal that the pyridine‐functionalized Fe₃O₄ nanoparticles are an efficient base catalyst for the domino condensation of various aromatic aldehydes, Meldrum's acid and 5‐methylpyrazol‐3‐amine under very mild reaction condition and in the presence of ethanol solvent. Moreover, the synthesized catalyst was used for one‐pot, three‐component condensation of aromatic aldehydes with barbituric acid and malononitrile to produce 7‐amino‐2,4‐dioxo‐5‐phenyl‐2,3,4,5‐tetrahydro‐1H‐pyrano[2,3‐d]pyrimidine‐6‐carbonitriles. All reactions are completed in short times and all products are obtained in good to excellent yields. Also, notably, the catalyst was reused five times without significant degradation in catalytic activity and performance. Copyright © 2016 John Wiley & Sons, Ltd.     

Synthesis of novel pyrazolo[3,4‐d]pyrimidines peri‐fused with 1,4‐diazepine, 1,4‐thiazepine,and 1,2,4‐triazepine rings

A simple and efficient synthesis of novel ortho‐ and peri‐annulated heterocyclic systems—2,6,7,9‐tetrahydro‐8H‐pyrazolo[5,4,3‐de]pyrimido[4,5‐e][1,4]diazepine, 2,6,7,9‐tetrahydro‐8H‐pyrazolo[5,4,3‐de]pyrimido [5,4‐f][1,4]thiazepine, and 6,9‐dihydro‐2H‐pyrazolo[3,4,5‐ef]pyrimido[5,4‐f][1,2,4]triazepine is described. J. Heterocyclic Chem.,, (2012).     

One pot syntheses of thiazol‐2‐hydrazone,pyridino[2,3‐d]pyridazine,pyrazolo[3,4‐d]pyridazine,and isoxazolo[4,5‐d]pyridazine derivatives

Reactions of the pyridazine derivatives 1a–c with phenyl isothiocyanate followed by heterocyclization with ethyl chloroacetate gave the thiazolidinone derivatives 6a–c . The reactivity of 6a towards some chemical reagents was studied. © 2002 Wiley Periodicals, Inc. Heteroatom Chem 13:258–262, 2002; Published online in Wiley Interscience (www.interscience.wiley.com). DOI 10.1002/hc.10026     

Synthesis and antimicrobial activity of some new pyrazole, fused pyrazolo[3,4-d]-pyrimidine and pyrazolo[4,3-e][1,2,4]-triazolo[1,5-c]pyrimidine derivatives

Hydrazonyl bromides 2a,b reacted with active methylene compounds (dibenzoylmethane, acetylacetone, ethyl acetoacetate, phenacyl cyanide, acetoacetanilide, ethyl cyanoacetate, cyanoacetamide and malononitrile) to afford the corresponding 1,3,4,5- tetrasubstituted pyrazole derivatives 5-12a,b. Reaction of 12a,b with formamide, formic acid and triethyl orthoformate give the pyrazolo[3,4-d]pyrimidine, pyrazolo[3,4- d]pyrimidin-4(3H)one and 5-ethoxymethylene-aminopyrazole-4-carbo-nitrile derivatives 13-15a,b, respectively. Compounds 15 a,b reacted with benzhydrazide and hydrazine hydrate to afford pyrazolo[4,3-e][1,2,4]triazolo[1,5-c]pyrimidine and [4-iminopyrazolo- [3,4-d]pyrimidin-5-yl]amine derivatives 16 a,b and 17 a,b. Reactions of compounds 17 a,b with triethyl orthoformate and carbon disulfide give the corresponding pyrazolo[4,3-e]- [1,2,4]triazolo[1,5-c]pyrimidine derivatives 18a,b and 19 a,b, respectively.     

Reactions of hydrazonoyl halides 43 : Synthesis of some new 2,3‐dihydro‐1,3,4‐thiadiazoles,pyrazoles, pyrazolo[3,4‐d]‐pyridazines,thieno[2,3‐b]pyridines,pyrimidino[4′,5′:4,5]thieno[2,3‐b]‐pyridines and pyrrolo[3,4‐d]pyrazoles

2,3‐Dihydro‐1,3,4‐thiadiazoles, pyrazoles, pyrazolo[3,4‐d]pyridazines, thieno[2,3‐b]pyridines, pyrim‐idino[4′,5′:4,5]thieno[2,3‐b]pyridines and pyrrolo[3,4‐d]pyrazoles were obtained in a good yields by treatment of hydrazonoyl halides with each of alkyl carbodithioates, 3‐(dimethylamino)‐1‐naphtho[1,2‐d]furan‐2‐ylprop‐2‐en‐1‐one and N‐arylmalemides.     

Novel synthesis of some new pyrimido[1,6‐a]pyrimidine and pyrazolo[1,5‐a]pyrimidine derivatives

An easy and efficient route for synthesis of some pyrimido[1,6‐a]pyrimidine and pyrazolo[1,5‐a]pyrimidine derivatives was described through the reaction of sodium salts of formyl ketones with 6‐aminothiouracil and 5‐aminopyrazole derivatives, respectively. The characterization of the reaction products was confirmed by using elemental analysis and spectral data. J. Heterocyclic Chem., (2012).