1,2,3-Triazolo[1,5-a]quinoxalines: synthesis and binding to benzodiazepine and adenosine receptors

Synthesis of 1,2,3-triazole-fused N-heterocycles from N-alkynyl hydroxyisoindolinones and sodium azide via the Huisgen reaction

An efficient methodology for the synthesis of dihydro[1,2,3]triazolo-pyrimidoisoindolones and dihydro[1,2,3]triazolo-diazepinoisoindolones has been developed using the Huisgen reaction from sodium azide and alkyne substituted amido alcohols in moderate to good yields. The reaction involves the in situ generation of the N-acyliminium ion intermediate, which undergoes a nucleophilic attack by the azide ion, followed by a [3 + 2]-intramolecular azide-alkyne cycloaddition reaction. Importantly, the reaction proceeds without the involvement of any transition metal catalyst. This methodology can be further utilized for the synthesis of dihydro[1,2,3]triazolo-pyrimidoisoindolthiones via thionation of amides.

Intramolecular Cyclization of Azido-Isocyanides Triggered by the Azide Anion: An Experimental and Computational Study

This work describes the unprecedented intramolecular cyclization occurring in a set of α-azido-ω-isocyanides in the presence of catalytic amounts of sodium azide. These species yield the tricyclic cyanamides [1,2,3]triazolo[1,5-a]quinoxaline-5(4H)-carbonitriles, whereas in the presence of an excess of the same reagent, the azido-isocyanides convert into the respective C-substituted tetrazoles through a [3 + 2] cycloaddition between the cyano group of the intermediate cyanamides and the azide anion. The formation of tricyclic cyanamides has been examined by experimental and computational means. The computational study discloses the intermediacy of a long-lived N-cyanoamide anion, detected by NMR monitoring of the experiments, subsequently converting into the final cyanamide in the rate-determining step. The chemical behavior of these azido-isocyanides endowed with an aryl-triazolyl linker has been compared with that of a structurally identical azido-cyanide isomer, experiencing a conventional intramolecular [3 + 2] cycloaddition between its azido and cyanide functionalities. The synthetic procedures described herein constitute metal-free approaches to novel complex heterocyclic systems, such as [1,2,3]triazolo[1,5-a]quinoxalines and 9H-benzo[f]tetrazolo[1,5-d][1,2,3]triazolo[1,5-a][1,4]diazepines.

Cu/Ag-Mediated One-Pot Enantioselective Synthesis of Fully Decorated 1,2,3-Triazolo[1,5-a]pyrazines

The synthesis of chiral triazole-fused pyrazine scaffolds from readily available substrates in a step-economical asymmetric catalytic way is highly appealing. We herein report that an efficient Cu/Ag relay catalyzed protocol employing cascade asymmetric propargylic amination, hydroazidation, and [3 + 2] cycloaddition reaction with high efficiency to access the target enantioenriched 1,2,3-triazolo[1,5-a]pyrazine has been accomplished by applying a novel N,N,P-ligand. The one-pot reaction of three components exhibits high functional group tolerance, excellent enantioselectivities, and a broad substrate scope with readily available starting materials.

Syntheses and Applications of 1,2,3-Triazole-Fused Pyrazines and Pyridazines

Pyrazines and pyridazines fused to 1,2,3-triazoles comprise a set of heterocycles obtained through a variety of synthetic routes. Two typical modes of constructing these heterocyclic ring systems are cyclizing a heterocyclic diamine with a nitrite or reacting hydrazine hydrate with dicarbonyl 1,2,3-triazoles. Several unique methods are known, particularly for the synthesis of 1,2,3-triazolo[1,5-a]pyrazines and their benzo-fused quinoxaline and quinoxalinone-containing analogs. Recent applications detail the use of these heterocycles in medicinal chemistry (c-Met inhibition or GABA_A modulating activity) as fluorescent probes and as structural units of polymers.

Synthesis of [1,2,3]Triazolo-[1,5-a]quinoxalin-4(5H)-ones through Photoredox-Catalyzed [3 + 2] Cyclization Reactions with Hypervalent Iodine(III) Reagents

An efficient synthesis of a variety of [1,2,3]triazolo-[1,5-a]quinoxalin-4(5H)-ones via a [3 + 2] cyclization reaction by photoredox catalysis between quinoxalinones and hypervalent iodine(III) reagents is reported. A range of quinoxalinones and hypervalent iodine(III) reagents were tolerated well. This cyclization reaction allows access to structurally diverse [1,2,3]triazolo-[1,5-a]quinoxalin-4(5H)-ones in moderate to good yields.

The Synthesis of 2-(1,2,3-Triazol-2-yl)-1,8-Naphthyridines under Microwave Irradiation

An efficient and convenient method is described for the synthesis of 3-aryl-2-(4,5-dimethyl-2H-1,2,3-triazol-2-yl)-1,8-naphthyridines (4) from α-acetylacetaldoxime 3-aryl-1,8-naphthyridin-2-ylhydrazones (3) in the presence of acetic anhydride and DMF using basic alumina as solid support under microwave irradiation.

Four-component, three-step cascade reaction: an effective synthesis of indazole-fused triazolo[5,1-c]quinoxalines

An efficient four-component, three-step cascade synthesis of indazole-fused triazolo[5,1-c]quinoxalines has been described. Notable features of this protocol include simple starting materials, reduced synthetic steps, and good yields.

1,2,3-Triazole-fused spirochromenes as potential anti-tubercular agents: synthesis and biological evaluation

A convenient synthesis of novel prototypes containing the two pharmacophores of chromene and 1,2,3-triazole in a single molecular backbone, were evaluated againstMycobacterium tuberculosisH37Rv strain.

Copper-Catalyzed Azidative Multifunctionalization of Alkynes

A facile and efficient copper-catalyzed azidative multifunctionalization of alkynes has been developed by using N-fluorobenzenesulfonimide (NFSI) as both nitrogen source and aryl source and trimethylsilyl azide (TMSN₃) as azido source. This transformation proceeds under mild conditions, providing a series of α-azido-α-aryl imine in good yields by a single operation starting from a wide range of alkynes. The prepared α-azido-α-aryl imines could be easily converted into 1,5-piperizine-fused 1,2,3-triazoles and azido enamines.

3-Iodothyroacetic acid (TA1), a by-product of thyroid hormone metabolism, reduces the hypnotic effect of ethanol without interacting at GABA-A receptors

3-iodothyroacetic acid (TA₁) is among the by-products of thyroid hormone metabolism suspected to mediate the non-genomic effects of the hormone (T3). We aim to investigate whether TA₁ systemically administered to mice stimulated mice wakefulness, an effect already described for T3 and for another T3 metabolite (i.e. 3-iodothryonamine; T1AM), and whether TA₁ interacted at GABA-A receptors (GABA-AR). Mice were pre-treated with either saline (vehicle) or TA₁ (1.32, 4 and 11 μg/kg) and, after 10 min, they received ethanol (3.5 g/kg, i.p.). In another set of experiments, TA₁ was administered 5 min after ethanol. The latency of sleep onset and the time of sleep duration were recorded. Voltage-clamp experiments to evaluate the effect of 1 μM TA₁ on bicuculline-sensitive currents in acute rat hippocampal slice neurons and binding experiments evaluating the capacity of 1, 10, 100 μM TA₁ to displace [³H]flumazenil from mice brain membranes were also performed. 4 μg/kg TA₁ increases the latency of onset and at 1.32 and 4 μg/kg it reduces the duration of ethanol-induced sleep only if administered before ethanol. TA₁ does not functionally interact at GABA-AR. Overall these results indicate a further similarity between the pharmacological profile of TA₁ and that of T₁AM.

A one-pot synthesis of [1,2,3]triazolo[1,5-a]quinoxalines from 1-azido-2-isocyanoarenes with high bond-forming efficiency

An efficient approach to prepare 1,2,3-triazolo[1,5-a]quinoxaline scaffolds, starting from 1-azido-2-isocyanoarenes and terminal acetylenes or substituted acetaldehydes, has been developed.

Design, Synthesis, and Biological Evaluation of Imidazo[1,5-a]quinoline as Highly Potent Ligands of Central Benzodiazepine Receptors

A series of imidazo[1,5-a]quinoline derivatives was designed and synthesized as central benzodiazepine receptor (CBR) ligands. Most of the compounds showed high CBR affinity with Ki values within the submicromolar and subnanomolar ranges with interesting modulations in their structure-affinity relationships. In particular, fluoroderivative 7w (Ki = 0.44 nM) resulted in the most potent ligand among the imidazo[1,5-a]quinoline derivatives described so far. Overall, these observations confirmed the assumption concerning the presence of a large though apparently saturable lipophilic pocket in the CBR binding site region interacting with positions 4 and 5 of the imidazo[1,5-a]quinoline nucleus. The in vivo biological characterization revealed that compounds 7a,c,d,l,m,q,r,w show anxiolytic and antiamnestic activities without the unpleasant myorelaxant side effects of the classical 1,4-BDZ. Furthermore, the effect of 7l,q,r, and 8i in lowering lactate dehydrogenase (LDH) release induced by ischemia-like conditions in rat brain slices suggested neuroprotective properties for these imidazo[1,5-a]quinoline derivatives.

A rapid entry to amino acid derived diverse 3,4-dihydropyrazines and dihydro[1,2,3]triazolo[1,5-a]pyrazines through 1,3-dipolar cycloaddition

Practical synthesis of diverse 3,4-dihydropyrazines, 6,7-dihydro-[1,2,3]triazolopyrazines and 7,8-dihydro-[1,2,3]triazolodiazepines through intramolecular 1,3-dipolar cycloaddition from amino acid derived intermediates is described.

Room-temperature Cu(ii)-catalyzed aromatic C–H azidation for the synthesis of ortho-azido anilines with excellent regioselectivity

An efficient synthesis of ortho-aniline derivatives through aromatic C–H azidation catalyzed by Cu(OAc)₂ have been disclosed. The amino group plays an ortho-directing effect in the azidation reactions, regiospecifically affording the mono-azidated derivative as the sole products.

Antimicrobial studies of unsymmetrical bis-1,2,3-triazoles

Aryl azides were treated with allenylmagnesium bromide to generate 1,5-disubstituted butynyl 1,2,3-triazoles in a domino fashion, which upon Cu(I) catalyzed 1,3-dipolar cycloaddition with aryl azides afforded novel bis-1,2,3-triazoles in quantitative yields. The final products were analyzed for their antimicrobial activities against a panel of bacterial and fungal strains which revealed the products to be potent antimicrobials.

New insight into the central benzodiazepine receptor-ligand interactions: design, synthesis, biological evaluation, and molecular modeling of 3-substituted 6-phenyl-4H-imidazo[1,5-a][1,4]benzodiazepines and related compounds

3-Substituted 6-phenyl-4H-imidazo[1,5-a][1,4]benzodiazepines and related compounds were synthesized as central benzodiazepine receptor (CBR) ligands. Most of the compounds showed high affinity for bovine and human CBR, their K(i) values spanning from the low nanomolar to the submicromolar range. In particular, imidazoester 5f was able to promote a massive flow of (36)Cl(-) in rat cerebrocortical synaptoneurosomes overlapping its efficacy profile with that of a typical full agonist. Compound 5f was then examined in mice for its pharmacological effects where it proved to be a safe anxiolytic agent devoid of the unpleasant myorelaxant and amnesic effects of the classical 1,4-benzodiazepines. Moreover, the selectivity of some selected compounds has been assessed in recombinant α(1)β(2)γ(2)L, α(2)β(1)γ(2)L, and α(5)β(2)γ(2)L human GABA(A) receptors. Finally, some compounds were submitted to molecular docking calculations along with molecular dynamics simulations in the Cromer's GABA(A) homology model.

Discovery of novel tricyclic full agonists for the G-protein-coupled niacin receptor 109A with minimized flushing in rats

Tricyclic analogues were rationally designed as the high affinity niacin receptor G-protein-coupled receptor 109A (GPR109A) agonists by overlapping three lead structures. Various tricyclic anthranilide and cycloalkene carboxylic acid full agonists were discovered with excellent in vitro activity. Compound 2g displayed a good therapeutic index regarding free fatty acids (FFA) reduction and vasodilation effects in rats, with very weak cytochrome P450 2C8 (CYP2C8) and cytochrome P450 2C9 (CYP2C9) inhibition, and a good mouse pharmacokinetics (PK) profile.

Characterization and preliminary use of 1-, 2- and 3-methyl-5-phenyl-7-chloro-1,2,3-triazolo[4,5-d]pyrimidine as reaction intermediates

This paper reports synthesis and characterization, by spectroscopic methods, of three new N-methyl-5-phenyl-7-chloro-1,2,3-triazolo[4,5-d]pyrimidine isomers 3a, 3b and 3c. For comparison purpose the 3-benzyl-5-phenyl-7-chloro-1,2,3-triazolo[4,5-d]pyrimidine (7) was also prepared. Starting from the isomer mixture 3a-c and the chloroderivative 7, by nucleophilic substitution reaction with ethyl carbazate and subsequent intramolecular cyclization, the new tricyclic derivatives 5a-c and 9 were prepared and tested towards the benzodiazepine and adenosine A1 and A2A receptors.

New 1,2,3-triazolo[1,5-a]quinoxalines: synthesis and binding to benzodiazepine and adenosine receptors. II

On pursuing research about 1,2,3-triazolo[1,5-a]quinoxalines, in this paper we report synthesis and binding assays toward the benzodiazepine and A(1) and A(2A) adenosine receptors, of a new series of derivatives, bearing some structural changes (introduction of fluorine and trifluoromethyl in the seventh position, amino substituents in the fourth position, benzyl group in the fifth position and aroyl substituents in the third position). The biological tests have shown that only the 7-fluorosubstituted compounds 3a and 4a and the N-benzyl derivative 7 have a good affinity toward the benzodiazepine receptors, while only the 7-trifluoromethyl substituted compound 3b presents a moderate affinity with low selectivity toward the A(1) adenosine receptors. The other structural modifications strongly decreased biological activity.

Substituted 1,2,3-triazolo[1,5-a]quinazolines: synthesis and binding to benzodiazepine and adenosine receptors

This paper reports the synthesis and evaluation of the biological affinity towards benzodiazepine and A(1) and A(2A) adenosine receptors of some 3-ethoxycarbonyl or 3-phenyl-substituted 1,2, 3-triazolo[1,5-a]quinazolines. Starting from the appropriate chloro-substituted phenylazides, the series of 7 or 8 chloro-substituted triazoloquinazolines were prepared. Nitration reactions of the triazoloquinazoline ring and chlorination reactions of the hydroxyl group in the 5 position of the same ring are also reported. By nucleophilic displacement of halogen, the corresponding 5-amino derivatives and some analogous derivatives bearing cyclohexylamino and p-toluidino substituents were obtained. The binding assays showed a generalized decrease in the affinity towards the benzodiazepine receptors and confirmed a moderate affinity towards the A(1) adenosine receptors in comparison with the previously studied triazoloquinazoline derivatives.