Search Results (8)

Although the hormone independent cytotoxic activity of several estradiol derivatives endowed with a simple substituent at C-2 has been reported so far, 2-heterocyclic and 2,3-condensed analogs are less investigated from both synthetic and pharmacological points of view. Therefore, novel A-ring-connected 2-pyrazoles of estradiol and, for comparison, their structurally simplified non-steroidal pairs were synthesized from estradiol 3-methyl ether and 6-methoxy-1,2,3,4-tetrahydronaphthalene. Friedel-Crafts acetylation of the protected phenolic compounds and subsequent O-demethylation led to ortho-substituted derivatives regioselectively, which were converted to arylhydrazones with phenylhydrazine, 4-tolylhydrazine and 4-chloro-phenylhydrazine, respectively, under microwave conditions. The hydrazones were subjected to cyclization with the Vilsmeier-Haack reagent immediately after preparation and the ring closure/formylation sequence resulted in steroidal and non-steroidal 4′-formylpyrazoles in moderate to good yields. During reductive transformations, 4-hydroxymethyl-pyrazoles were obtained, while oxidative lactonization of the 4-formylpyrazole moiety with the phenolic OH in the presence of the Jones reagent afforded A-ring-integrated pyrazolocoumarin hybrids and related analogs. Steroidal pyrazoles, which were produced as C-17 acetates due to acetylation of C-17 OH during the primary Friedel-Crafts reaction, underwent deacetylation in alkaline methanol to furnish 2-heterocyclic estradiol derivatives. Pharmacological studies revealed the overall and cancer cell-specific cytotoxicity of the derivatives and the half maximal inhibitory concentrations were obtained for the most promising compounds. Full article

A simple general synthesis of 1-aryl-6-azaisocytosine-5-carbonitriles 4 is described. This method is based on coupling diazonium salts with cyanoacetylcyanamide 2 and then cyclization of the formed 2-arylhydrazono-2-cyanoacetylcyanamides 3. The 6-azaisocytosines 4 were studied with respect to tautomeric equilibrium and the transformation of functional groups, and used in the synthesis of the condensed heterocyclic compounds: Purine isosteric imidazo[2,1-c]-[1,2,4]triazine 8 and the 1,2,4-triazino[2,3-a]quinazolines 9–12. Full article

An efficient route to substituted 1-aryl-1H-indazoles has been developed and optimized. The method involved the preparation of arylhydrazones from acetophenone or benzaldehyde substituted by fluorine at C2 and nitro at C5, followed by deprotonation and nucleophilic aromatic substitution (S_NAr) ring closure in 45–90%. Modification of this procedure to a one-pot domino process was successful in the acetophenone series (73–96%), while the benzaldehyde series (63–73%) required a step-wise addition of reagents. A general one-pot protocol for 1-aryl-1H-indazole formation without the limiting substitution patterns required for the S_NAr cyclization has also been achieved in 62–78% yields. A selection of 1-aryl-1H-indazoles was prepared in high yield by a procedure that requires only a single laboratory operation. Full article

The 4-thiazolidinones 3a–d were used as a key intermediates for the synthesis of 2-arylimino-5-arylidene-4-thiazolidinones derivatives 7a–p via nucleophilic addition reactions with the arylidene malononitrile. Moreover the 4-thiazolidinones 3a and 3c condensed with the DMF-DMA to form the corresponding enamines 8 and 9 depending on the reaction conditions. Otherwise the 4-thiazolidinone 3b reacts regioselectively with DMF-DMA to afford the enaminones 10 and 11, respectively. The latter reacts with many heterocyclic amines affording polyfunctionally substituted fused pyrimidine derivatives 13–18. The enamine 8b was also reacted with the 3-amino-1,2,4-triazole to afford the acyclic product 19, which could not be further cyclized to the corresponding tricyclic system 20. Moreover the 4-thiazolidinone 3c reacted with the benzenediazonium chloride to afford the arylhydrazones 12. The X-ray single crystal technique was employed in this study for structure elucidation and Z/E potential isomerism configuration determination. The X-ray crystallographic analyses of eight products could be obtained, thus establishing with certainty the structures proposed in this work. Full article

The molecular structures of nine 3-methyl-1-phenyl-1H-chromeno[4,3-c]pyrazol-4-one isomers, obtained by the oxidative cyclization of the corresponding 1-phenylhydrazono chromen-2-ones with copper acetate as catalyst, are reported. The molecular and supramolecular structures of the 8-chloro, 8-bromo- and 8-nitro isomers 2b-d, were established by X-ray diffraction. The halogenated isomers 2b and 2c are isomorphs, they crystallize as a triclinic system, space group P-1 with two molecules in the asymmetric unit. Compound 2d crystallizes as a monoclinic system, space group P2₁/m with two molecules in the unit cell. The 1-phenyl ring [Cg(4)] is almost perpendicularly positioned to the chromene-pyrazole ring system. This conformation is in agreement with the anisotropic NMR shielding effect exerted by the phenyl ring over H-9 in solution. The supramolecular architecture is almost controlled by C―H···A (A = O, p) and face to face p-stacking interactions. The observed p-stacking trend between chromene and pyrazole rings is given by the overlapping between the best donor and acceptor rings in each compound. Full article

2-Pyridylacetonitrile (1) couples with aromatic diazonium salts to yield arylhydrazones 2a-c, that were shown to exist in the syn-form 2 rather than the anti-form 4. Compounds 2a,c reacted with hydroxylamine in refluxing DMF to yield the interesting 1,2,3-triazolylpyridines 6. Attempts to cyclize 2 to give the corresponding fused pyrazolopyridines 9 failed. On the other hand, compound 1 condensed with dimethylformamide dimethyl acetal to yield enaminonitrile 10 that could be converted into pyrazolylpyridine 11. Full article

2-(1-(4-Bromophenyl)-2-thiocyanatoethylidene)malononitrile (3) undergoes azo coupling with diazotized aromatic amines to afford arylhydrazone derivatives, which are readily cyclized to afford the corresponding 3(2H)-pyridazinimine derivatives upon reflux in aqueous NaOH. Under similar condition an o-cyanoarylhydrazone derivative was cyclized into 6H-pyridazino[1,6-a]quinazolin-6-imine, which in turn was easily transformed into 6H-pyridazino[1,6-a]quinazolin-6-one on reflux in ethanolic/HCl. Compound 3 afforded substituted 5-acetylthiophene derivatives upon reflux in AcOH/HCl mixtures. Full article

Reaction of 2-hydrazino-3-methyl-3,4-dihydrothieno[2,3-d]pyrimidin-4-one derivatives 2a,b with aliphatic acids afforded the thienotriazolopyrimidinone derivatives 3a-d, with nitrous acid yielded tetrazolothienopyrimidinone derivatives 4a,b and with carbon disulphide furnished 3-mercaptothienotriazolopyrimidinone derivatives 5a,b. Also, 2a,b reacted with aldehydes to afford the arylhydrazones 6a-f which cyclized into thienotriazolopyrimidinone derivatives 7a-f. Furthermore, 2a,b condensed with ethyl acetoacetate and ethyl cyanoacetate to afford 2-(1-pyrazolyl) derivatives 9a,b and 10a,b, respectively. On the other hand, 2-hydrazino derivatives 2a,b condensed with a-halo-ketones to yield thienpyrimidotriazinone derivatives 11a,b and with β-diketones, to form 2-(1-pyrazolyl) derivatives 12a-f. Full article