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Showing papers on "Piperidine published in 2015"


Journal ArticleDOI
TL;DR: A new method for metal-free intramolecular C-H amination has been developed that combines electrochemical oxidation of 2-pyrimidyloxybenzenes with the treatment of the resulting pyrimidinium ions with piperidine to give 2-aminobenzoxazoles and 2-aminsobenzothiazoles.
Abstract: A new method for metal-free intramolecular C-H amination has been developed. Electrochemical oxidation of 2-pyrimidyloxybenzenes and 2-pyrimidylthiobenzenes, which can be easily prepared from phenols and thiophenols, respectively, followed by the treatment of the resulting pyrimidinium ions with piperidine gives 2-aminobenzoxazoles and 2-aminobenzothiazoles, respectively.

67 citations


Journal ArticleDOI
TL;DR: In this paper, a nanocomposites for one-pot synthesis of aminoindolizines via A3 coupling reaction in the presence of ethylene glycol (EG) as a recyclable solvent.
Abstract: CuI/CSP nanocomposites were found to be efficient and recyclable nanocatalysts for one-pot synthesis of aminoindolizines via A3 coupling reaction in the presence of ethylene glycol (EG) as a recyclable solvent. In contrast, chalcones were isolated when the reaction was performed in the presence of secondary amines such as piperidine, 3-methylpiperidine, pyrrolidine, and piperazine under solvent free conditions. The CuI/CSP was recycled for five times without significant loss in its catalytic activity. The anomalous selectivity in the formation of aminoindolizines and chalcones was dependent on solvents and secondary amines used for the reaction. The present methodology is facile and follows green principles with higher atom economy (94%) and smaller E-factor (0.06).

43 citations


Journal ArticleDOI
TL;DR: The presence of the meso-1,2-diphenylethylenediamine moiety in metal complexes of this type may provide a general method for instilling selectivity for some DNA quadruplexes over dsDNA.
Abstract: As part of a program of preparing metal complexes which exhibit unique affinities towards different DNA structures, we have synthesised the novel Schiff base complex N,N′-bis-4-(hydroxysalicylidine)meso-diphenylethylenediaminenickel(II) (4), via the reaction of meso-1,2-diphenylethylenediamine and 2,4-dihydroxybenzaldehyde. This compound was subsequently reacted with 1-(2-chloroethyl)piperidine or 1-(2-chloropropyl)piperidine, to afford the alkylated complexes N,N′-bis-(4-((1-(2-ethyl)piperidine)oxy)salicylidine)meso-1,2-diphenylethylenediaminenickel(II) (5) and N,N′-bis-(4-((1-(3-propyl)piperidine)oxy)-salicylidine)meso-1,2-diphenylethylenediaminenickel(II) (6), respectively. These complexes were characterised by microanalysis and X-ray crystallography in the solid state, and in solution by 1H and 13C NMR spectroscopy. Electrospray ionisation mass spectrometry (ESI-MS) was used to confirm the identity of (5) and (6). The affinities of (5) and (6) towards a discrete 16 mer duplex DNA molecule, and examples of both tetramolecular and unimolecular DNA quadruplexes, was explored using a variety of techniques. In addition, the affinity of two other complexes (2) and (3), towards the same DNA molecules was examined. Complexes (2) and (3) were prepared by methods analogous to those which afforded (5) and (6), however 1,2-phenylenediamine was used instead of meso-1,2-diphenylethylenediamine in the initial step of the synthetic procedure. The results of ESI-MS and DNA melting temperature measurements suggest that (5) and (6) exhibit a lower affinity than (2) and (3) towards the 16 mer duplex DNA molecule, while circular dichroism (CD) spectroscopy suggested that none of the four complexes had a major effect on the conformation of the nucleic acid. In contrast, ESI-MS and CD spectroscopy suggested that both (5) and (6) show significant binding to a tetramolecular DNA quadruplex. The results of ESI-MS and Fluorescence Resonance Energy Transfer (FRET) assays indicated that (5) and (6) did not bind as tightly to a unimolecular DNA quadruplex, although both complexes had a major effect on the CD spectrum of the latter. These results highlight that the presence of the meso-1,2-diphenylethylenediamine moiety in metal complexes of this type may provide a general method for instilling selectivity for some DNA quadruplexes over dsDNA.

38 citations


Journal ArticleDOI
TL;DR: A direct approach to the synthesis of polyhydroxylated piperidine and pyrrolidine peptidomimetics is described, based on one-pot reduction of sugar-derived lactams with Schwartz's reagent followed by a multicomponent Ugi-Joullié reaction.
Abstract: A direct approach to the synthesis of polyhydroxylated piperidine and pyrrolidine peptidomimetics is described. The presented strategy is based on one-pot reduction of sugar-derived lactams with Schwartz’s reagent followed by a multicomponent Ugi–Joullie reaction.

38 citations


Journal ArticleDOI
TL;DR: 2-Aryltetrahydropyridines formed by anionic cyclization or ring-closing metathesis were converted to their N'-aryl urea derivatives and related chemistry was observed in pyrroline homologues.

36 citations


Journal ArticleDOI
TL;DR: A series of highly functionalized piperidine derivatives was synthesized through one-pot, five-component reaction of aldehydes, amines, and β-ketoesters as mentioned in this paper.

31 citations


Journal ArticleDOI
TL;DR: An organocatalyzed asymmetric tandem reaction of cyclic N-sulfonylimines and α,β-unsaturated aldehydes was developed, affording similar piperidine derivatives.

31 citations


Journal ArticleDOI
TL;DR: An efficient and one-pot multi-component procedure for the preparation of functionalized piperidine derivatives from reactions of aromatic aldehydes, substituted anilines and ethyl acetoacetate in the presence of ferric hydrogen sulfate-supported silica-coated magnetic nanoparticles (NiFe2O4@SiO2-FHS) as a magnetically recyclable green catalyst has been developed as mentioned in this paper.
Abstract: An efficient and one-pot multi-component procedure for the preparation of functionalized piperidine derivatives from reactions of aromatic aldehydes, substituted anilines and ethyl acetoacetate in the presence of ferric hydrogen sulfate-supported silica-coated magnetic nanoparticles (NiFe2O4@SiO2-FHS) as a magnetically recyclable green catalyst has been developed. The catalysts show environmentally benign character, which can be easily prepared, stored, and recovered several times without obvious significant loss of activity.

31 citations


Journal ArticleDOI
TL;DR: In this article, the 2,6-sas cyclotetraphosphazenes were synthesized with mono-and diamines, and the results were verified by elemental analyses, MS, FTIR, 1H, 13C{1H}, 31P NMR, HSQC, HMBC and X-ray crystallography.

25 citations


Journal ArticleDOI
TL;DR: Three titanium-containing ligands are shown to assemble active catalysts in situ and enable catalysis at room temperature, and a variety of sterically bulky secondary amines are efficiently allylated in high yields with as little as 1 mol % palladium catalyst.

25 citations


Journal ArticleDOI
TL;DR: 1,2- diphenylethylamines appears to reflect the exploration of alternatives to arylcyclohexylamine-type substances, such as methoxetamine, PCP and PCPy-based analogues that also show NMDA receptor activity as demonstrated here for diphenidine.
Abstract: © 2014 John Wiley & Sons, Ltd. Substances with the diphenylethylamine nucleus represent a recent addition to the product catalog of dissociative agents sold as 'research chemicals' on the Internet. Diphenidine, i.e. 1-(1,2-diphenylethyl)piperidine (1,2-DEP), is such an example but detailed analytical data are less abundant. The present study describes the synthesis of diphenidine and its most obvious isomer, 1-(2,2-diphenylethyl)piperidine (2,2-DEP), in order to assess the ability to differentiate between them. Preparation and characterization were also extended to the two corresponding pyrrolidine analogues 1-(1,2-diphenylethyl)- and 1-(2,2-diphenylethyl)pyrrolidine, respectively. Analytical characterizations included high-resolution electrospray mass spectrometry (HR-ESI-MS), liquid chromatography ESI-MS/MS, gas chromatography ion trap electron and chemical ionization MS, nuclear magnetic resonance spectroscopy (NMR) and infrared spectroscopy. Differentiation between the two isomeric pairs was possible under GC-(EI/CI)-MS conditions and included the formation of distinct iminium ions, such as m/z 174 for 1,2-DEP and m/z 98 for 2,2-DEP, respectively. The pyrrolidine counterparts demonstrated similar phenomena including the expected mass difference of 14 Da due to the lack of one methylene unit in the ring. Two samples obtained from an Internet vendor provided confirmation that diphenidine was present in both samples, concurring with the product label. Finally, it was confirmed that diphenidine (30 μM) reduced N-methyl-D-aspartate-mediated field excitatory postsynaptic potentials (NMDA-fEPSPs) to a similar extent to that of ketamine (30 μM) when using rat hippocampal slices. The appearance of 1,2- diphenylethylamines appears to reflect the exploration of alternatives to arylcyclohexylamine-type substances, such as methoxetamine, PCP and PCPy-based analogues that also show NMDA receptor activity as demonstrated here for diphenidine.

Journal ArticleDOI
TL;DR: In this paper, a bi-component organocatalyst system was proposed for the condensation of acetone to prepare mesityl oxide (MO), an important intermediate in the chemical industry.
Abstract: Unexpectedly, L-proline/piperidine was found to be a better recyclable catalyst system than L-proline or piperidine alone in the condensation of acetone to prepare mesityl oxide (MO), an important intermediate in the chemical industry. Binding the catalyst system onto polymer resin enhanced the MO selectivity and reduced the catalyst loss. The mechanism of the bi-component catalyst system was also studied through control reactions, as well as by dynamic calculations. The MO selectivity could reach 74.4% and its isolated yield could reach 73.9%, based on the consumed acetone. Although the result does not immediately meet the requirement of industrial production, this study provides a novel organocatalyst system, which might offer a potential alternative to traditional inorganic catalysts that can be used under mild and neutral conditions.

Journal ArticleDOI
TL;DR: In this article, the reactions of O,O-diethyl 2,4-dinitrophenylphosphate triester with piperidine in ionic liquids and four conventional organic solvents (COS) were subjected to kinetic and product studies.
Abstract: The reactions of O,O-diethyl 2,4-dinitrophenylphosphate triester (1) with piperidine in ionic liquids and four conventional organic solvents (COS) were subjected to kinetic and product studies. Analytical techniques (UV-vis and NMR) identified two pathways: nucleophilic attack at the phosphoryl center and at the C-1 aromatic carbon. The nucleophilic rate constants (kTN) for these parallel reactions were separated into two terms: kPN and kArN for the corresponding electrophilic centers. Both the rate and the selectivities of the reactions are strongly dependent on the nature of the ionic liquid used, and a good correlation with the solvent acceptor capacity to form hydrogen bonds (β) was observed. Remarkably, an exclusive attack at the phosphoryl center was found using [Bmim]DCA, [Bmpyrr]DCA and [Bmpy]DCA as the reaction solvents. In contrast, with [Bmim]PF6 as the reaction solvent, attack at the C-1 aromatic was the main path (94%). These results suggest that ionic liquids can be considered to be designer solvents because by an appropriate choice of the anion it is possible to steer the selectivity of this reaction.

Journal ArticleDOI
01 Jan 2015-Ionics
TL;DR: In this paper, the authors investigated the inhibition ability of three newly synthesized piperidine sulphonamides toward mild steel (MS) corrosion using mass loss and electrochemical techniques, and the results indicated that all the studied inhibitors act as mixed type of corrosion inhibitors.
Abstract: The inhibition ability of three newly synthesized piperidine sulphonamides toward the mild steel (MS) corrosion was investigated using mass loss and electrochemical techniques. The adsorption of all the piperidine sulphonamides on MS complies with the Langmuir isotherm model in all studied temperatures. Associated activation and adsorption thermodynamic parameters were computed and discussed. The polarization results indicated that all the studied inhibitors act as mixed type of corrosion inhibitors. The protective layer of organic compounds on MS surface was confirmed by scanning electron microscopy (SEM). The values of free energy of adsorption (ΔG ads) revealed that the inhibitors adsorbed on the MS surface via both chemisorption and physisorption mechanisms. The relationship between inhibition efficiency and molecular structures of inhibitors was discussed using quantum chemical parameters. The inhibition efficiencies obtained from mass loss and electrochemical measurements were in good agreement.

Journal ArticleDOI
TL;DR: In this paper, 1,4-dihydropyridines were synthesized via catalytic enantioselective cyclization reactions of β,γ-unsaturated α-ketoesters, arylamines and acetylacetone for the first time.
Abstract: Penta-substituted 1,4-dihydropyridines were synthesized via catalytic enantioselective cyclization reactions of β,γ-unsaturated α-ketoesters, arylamines and acetylacetone for the first time. H 8 -BINOL-type chiral imidodiphosphoric acid 4c was a suitable catalyst and exhibited high catalytic and stereocontrolling abilities in these enone-type reactions. Under the optimized conditions, these 1,4-dihydropyridines were obtained with excellent enantioselectivities (up to 97% ee). In addition, the typical product 8ba was converted into the corresponding substituted piperidine with high yield (87%) and excellent enantioselectivity (95% ee) in a single-step reduction.

Journal ArticleDOI
TL;DR: The present review emphasizes on the synthetic aspects of p Piperine along with the structure-activity relationships of its derivatives so as to rationalize the discovery of newer piperine based molecules.
Abstract: Piperine is the main constituent of pepper, a commonly used kitchen spice and has been reported to possess various pharmacological activities. The structural features, an aromatic ring with a methylenedioxy bridge, a conjugated dienone system and a piperidine ring constituting an amide bond, possessed by the molecule have been considered important for the molecule to exhibit an array of bioactivities. Several modifications of above structural units have affected the biological properties of piperine, either enhancing or in some cases completely abolishing the activity. The present review emphasizes on the synthetic aspects of piperine along with the structure-activity relationships of its derivatives so as to rationalize the discovery of newer piperine based molecules.

Journal ArticleDOI
TL;DR: In this article, a series of benzo[4,5]imidazo[1,2-a ]pyridine derivatives is synthesized through the reaction of 2-(1 H -benzo[d ]imidazol-2-yl)acetonitrile and different ethyl 2,4-dioxo-4-arylbutanoate derivatives in the presence of piperidine in refluxing EtOH.

Journal ArticleDOI
TL;DR: The cascade aza-Cope/aza-Prins cyclization of homoallylamines to give substituted piperidines has been explored in this article, where the use of glyoxalic acid as the carbonyl component afforded bicyclic structures as a result of the internal carboxylate anion trapping the intermediate cation.

Journal ArticleDOI
TL;DR: A series of naphthaldehydes, including a Mannich base, have been investigated by UV-Vis spectroscopy, NMR and theoretical methods to explore their potential tautomerism and crystallographic data, obtained for the latter, confirm the existence of a cyclic dimer.
Abstract: A series of naphthaldehydes, including a Mannich base, have been investigated by UV-Vis spectroscopy, NMR and theoretical methods to explore their potential tautomerism. In the case of 4-hydroxy-1-naphthaldehyde concentration dependent deprotonation has been detected in methanol and acetonitrile. For 4-hydroxy-3-(piperidin-1-ylmethyl)-1-naphthaldehyde (a Mannich base) an intramolecular proton transfer involving the OH group and the piperidine nitrogen occurs. In acetonitrile the equilibrium is predominantly at the OH-form, whereas in methanol the proton transferred tautomer is the preferred form. In chloroform and toluene, the OH form is completely dominant. Both 4-hydroxy-1-naphthaldehyde and 4-methoxy-1-naphthaldehyde (fixed enol form) show dimerization in the investigated solvents and the crystallographic data, obtained for the latter, confirm the existence of a cyclic dimer.

Journal ArticleDOI
Xiao Zheng1, Jiang He1, Heng-Hui Li1, Ao Wang1, Xi-Jie Dai1, Ai-E Wang1, Pei-Qiang Huang1 
TL;DR: An umpolung Mannich-type reaction of secondary amides, aliphatic aldehydes, and electrophilic alkenes has been disclosed and its synthetic utility has been demonstrated by a facile construction of the tricyclic core of marine alkaloids such as cylindricine C and polycitorol A.
Abstract: An umpolung Mannich-type reaction of secondary amides, aliphatic aldehydes, and electrophilic alkenes has been disclosed. This reaction features the one-pot formation of C-N and C-C bonds by a titanocene-catalyzed radical coupling of the condensation products, from secondary amides and aldehydes, with electrophilic alkenes. N-substituted γ-amido-acid derivatives and γ-amido ketones can be efficiently prepared by the current method. Extension to the reaction between ketoamides and electrophilic alkenes allows rapid assembly of piperidine skeletons with α-amino quaternary carbon centers. Its synthetic utility has been demonstrated by a facile construction of the tricyclic core of marine alkaloids such as cylindricine C and polycitorol A.

Journal ArticleDOI
TL;DR: The design, synthesis, binding evaluation and binding evaluation against σ1 and σ2 receptors of a series of new piperidine-4-carboxamide derivatives variously substituted on the amide nitrogen atom are reported.


Journal ArticleDOI
TL;DR: 1,2,5,6-Tetrahydropyridine (THP), piperidine derivatives, antibacterial, antifungal, antioxidant, and antioxidant activities are synthesized and evaluated using agar disc diffusion and 2,2-diphenyl-1-picrylhydrazyl (DPPH) scavenging capacity.
Abstract: Six novel piperidine derivatives, compounds 5 to 10, have been synthesized and their antimicrobial and anti-oxidant activities evaluated using agar disc diffusion (antimicrobial) and 2,2-diphenyl-1-picrylhydrazyl (DPPH) scavenging capacity (antioxidant). Compound 9 revealed the least antibacterial activity. Compound 6 exhibited the strongest inhibitory activity and the best minimum inhibitory concentration (MIC) results against the seven bacteria tested in comparison to the other piperidine derivatives (5, 7, 8, 9, and 10). All six piperidine compounds displayed no activity against fungal species, Fusarium verticilliodes, Candida utilus and Penicillium digitatium. Compounds 7 and 8 revealed no activity against all seven fungi tested. Compounds 5, 6, 9, and 10 revealed varying degree of inhibition against Aspergillus niger, Aspergillus flavus, Saccharomyces cerevisiae and Candida albicans. Compound 8 demonstrated the highest scavenging capacity of 78% at 1000 µg/ml and compound 6 demonstrated the least percentage of scavenging potential of 49% at 1000 µg/ml. All piperidine derivatives tested, revealed antioxidant potentials greater than 49% at 1 mg/ml as compared to the control Rutin, which displayed 97% scavenging capacity at the same concentration. All piperidine derivatives revealed varying degree of antimicrobial and antioxidant activities. Key words: 1,2,5,6-Tetrahydropyridine (THP), piperidine derivatives, antibacterial, antifungal, antioxidant.

Journal ArticleDOI
TL;DR: In this article, a general method to assemble multi-substituted chiral piperidines was developed, inspired by the biosynthesis of piperidine natural products, which could be accomplished by a vinylogous type Mannich reaction if a functionalized dienolate was employed.
Abstract: A general method to assemble multi-substituted chiral piperidines was developed, inspired by the biosynthesis of piperidine natural products. In biosynthesis, Δ1-piperideine 4 plays a key role as a common intermediate giving rise to a variety of piperidine-based natural alkaloids. Nature uses L-lysine as a building block, enzymatically transforming it into a δ-amino carbonyl intermediate 3 as the precursor to cyclize into Δ1-piperideine 4. We envisioned that such a process could be accomplished by a vinylogous type Mannich reaction if a functionalized dienolate was employed. A stereoselective three-component vinylogous Mannich-type reaction (VMR) of 1,3-bis-trimethylsily enol ether 7 was therefore investigated and was found to give cyclized chiral dihydropyridinone compound 9 as an adduct. Like Δ1-piperideine in biosynthesis, the chiral 2,3-dihydropyridinone compound 9 from VMR is a versatile intermediate for building a variety of new chiral piperidine compounds. The method was showcased by concise two-step approaches in the synthesis of the bioactive natural alkaloids (+)-241D; (−)-241D and isosolenopsin A. Furthermore, when properly functionalized substrate aldehyde 24 was employed, the corresponding dihydropyridinone adduct 25 cyclized to form a second piperidine ring, leading to a chiral polyfunctional quinolizidine enaminone 27. This versatile intermediate was used to prepare a variety of new chiral quinolizidine compounds, including natural alkaloid (−)-epimyrtine.

Journal ArticleDOI
TL;DR: In this article, new organic dyes comprising phenothiazine, carbazole, indole, diphenylamine moieties, as the electron donors, and coumarin ring as electron acceptor through ethylenic π bridge were synthesized and characterized.

Journal ArticleDOI
TL;DR: High stereoselective carbolithiation reactions of α-aryl piperidine enecarbamates that offer direct access to vicinally-substituted piperidines and it is demonstrated that the carbanion intermediates can be trapped with a carbon electrophile.

Journal ArticleDOI
TL;DR: This approach can be used for the synthesis of highly substituted piperidine derivatives and can be reduced stereoselectively, and up to five consecutive stereogenic centers can be obtained.
Abstract: Chiral α-amino ketones are excellent nucleophiles for stereoselective palladium-catalyzed allylic alkylations. Both chiral as well as achiral allylic substrates can be applied, while the stereochemical outcome of the reaction is controlled by the chiral ketone enolate. The substituted amino ketones formed can be reduced stereoselectively, and up to five consecutive stereogenic centers can be obtained. This approach can be used for the synthesis of highly substituted piperidine derivatives.

Journal ArticleDOI
TL;DR: In this paper, reaction of N-arylacetoacetamides with aromatic aldehydes in the presence of piperidine in ethanol afforded N,N′,2-triaryl-6-hydroxy 6-methyl-4-oxocyclohexane-1,3-dicarboxamides.
Abstract: Reaction of N-arylacetoacetamides with aromatic aldehydes in the presence of piperidine in ethanol afforded N,N′,2-triaryl-6-hydroxy-6-methyl-4-oxocyclohexane-1,3-dicarboxamides. The latter reacted with p-toluidine leading to the formation of dehydration products. Reactions of N,N′,2-triaryl-6-hydroxy-6-methyl-4-oxocyclohexane-1,3-dicarboxamides with hydrazine hydrate and cyanoacetic acid hydrazide gave rise to tetrahydroindazoles. Some of the obtained compounds showed antimicrobial activity.

Journal ArticleDOI
TL;DR: In this paper, a three-component reaction of isatin, ethyl cyanoacetate, and 1,2,3,4,5,6-hexahydro-2-(nitromethylidene)pyrimidine was used to synthesize carbonitrile.
Abstract: An efficient synthesis of (3S)-1,1′,2,2′,3′,4′,6′,7′-octahydro-9′-nitro-2,6′-dioxospiro[3H-indole-3,8′-[8H]pyrido[1,2-a]pyrimidine]-7′-carbonitrile is achieved via a three-component reaction of isatin, ethyl cyanoacetate, and 1,2,3,4,5,6-hexahydro-2-(nitromethylidene)pyrimidine. The present method does not involve any hazardous organic solvents or catalysts. Also the synthesis of ethyl 6′-amino-1,1′,2,2′,3′,4′-hexahydro-9′-nitro-2-oxospiro[3H-indole-3,8′-[8H]pyrido[1,2-a]pyrimidine]-7′-carboxylates in high yields, at reflux, using a catalytic amount of piperidine, is described. The structures were confirmed spectroscopically (IR, 1H- and 13C-NMR, and EI-MS data) and by elemental analyses. A plausible mechanism for this reaction is proposed (Scheme 2).

Journal ArticleDOI
TL;DR: In this article, N′-((2-Chloroquinolin-3-yl)methylene)-2-cyanoacetohydrazide (3) was synthesized then treated with aromatic aldehydes in basic medium to afford the arylidene derivatives 4a-e.
Abstract: N′-((2-Chloroquinolin-3-yl)methylene)-2-cyanoacetohydrazide (3) was synthesized then treated with aromatic aldehydes in basic medium to afford the arylidene derivatives 4a–e. Reaction of 4a–c with hydrazine hydrate in boiling ethanol gave the 3-aminopyrazoles 5a–c. Base promoted Michael addition of 3 to arylidene malononitriles 6 afforded 2-pyridones 9a–d. Cyclocondensation of 3 with some salicylaldehyde derivatives gave the iminocoumarins 10a–c; these underwent acid-catalyzed hydrolysis to give coumarins 11a–c. Coupling of 3 with arene diazonium chloride in pyridine afforded the arylhydrazononitriles 12a–c. Heterocyclization of 12a with formalin and piperidine in warm ethanol gave the 1,2,4-triazine derivative 13. The mechanisms and the chemoselectively of these reactions are discussed. The newly synthesized compounds were tested for antibacterial and anticancer activity. Pyridone 9b and coumarin 11c had the most potent antibacterial activity against S. aureus. Acrylamide 4d, pyridones 9a, c, and 1,2,4-triazine 13 were the most active anticancer compounds, with a broad range of activity against most of the tumor cell lines tested.