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Dual inhibitors of protein phosphotyrosine phosphatase 1B (PTP1B)/T-cell protein phosphotyrosine phosphatase (TC-PTP) based on the 3-(hydroxymethyl)-4-oxo-1,4-dihydrocinnoline scaffold have been identified. Their dual affinity to both enzymes has been thoroughly corroborated by in silico modeling experiments. The compounds have been profiled in vivo for their effects on body weight and food intake in obese rats. Likewise, the effects of the compounds on glucose tolerance, insulin resistance, as well as insulin and leptin levels, have been evaluated. In addition, the effects on PTP1B, TC-PTP, and Src homology region 2 domain-containing phosphatase-1 (SHP1), as well as the insulin and leptin receptors gene expressions, have been assessed. In obese male Wistar rats, a five-day administration of all studied compounds led to a decrease in body weight and food intake, improved glucose tolerance, attenuated hyperinsulinemia, hyperleptinemia and insulin resistance, and also compensatory increased expression of the PTP1B and TC-PTP genes in the liver. The highest activity was demonstrated by 6-Chloro-3-(hydroxymethyl)cinnolin-4(1H)-one (compound 3) and 6-Bromo-3-(hydroxymethyl)cinnolin-4(1H)-one (compound 4) with mixed PTP1B/TC-PTP inhibitory activity. Taken together, these data shed light on the pharmacological implications of PTP1B/TC-PTP dual inhibition, and on the promise of using mixed PTP1B/TC-PTP inhibitors to correct metabolic disorders. [ABSTRACT FROM AUTHOR]

The structural modification of phthalazinones and indazolones has emerged as a pivotal topic in catalytic C–H functionalization events. Herein we report the hydrazide-assisted rhodium(III)-catalyzed cross-coupling reactions of N -arylphthalazinones and N -arylindazolones with vinylene carbonate. This method provides direct access to tetracyclic hydroxycinnolines. Complete site-selectivity and functional group compatibility were observed. [ABSTRACT FROM AUTHOR]

The Richter cyclization was used for the synthesis of 6-halo-3-(hydroxymethyl)cinnolin-4(1H)-ones. X-ray analysis revealed that these compounds exist as dimers in their crystal state, wherein two molecules are linked by intermolecular double and bifurcated hydrogen bonds that can explain their low solubility. Theoretical study of bifurcated hydrogen bonds responsible for the dimerization was carried out by DFT calculations as well as by topological analysis of the electron density distribution within the framework of Bader's theory. [ABSTRACT FROM AUTHOR]

Straightforward method for the synthesis of pyrrolo[1,2-b]cinnolines starting from 2-nitrobenzaldehydes and 2-methylfurans has been elaborated. The key steps of the process are oxidative furan ring opening with diazonium cation and intramolecular alkylation of azo group of the resulted cinnoline with secondary allyl alcohol. [ABSTRACT FROM AUTHOR]

A new series of cinnoline-1,2,3-triazole derivatives were designed and synthesized by adopting Cu(1) catalyzed regeoselective1,3-dipolar cycloaddition reaction of terminal alkyne and azide. The in vitro antibacterial activity of all these compounds revealed that compounds 9d, 10a, 10b, and 10c are more potent antibacterial agents. Among the series, compound 4-(3-(4-((cinnolin-4-yloxy)methyl)-1H-1,2,3-triazol-1-yl)propyl)morpholine (10b) exhibited the most potent antibacterial activity against all tested gram-positive and gram-negative bacterial strains. Furthermore, molecular docking studies were also performed to understand the binding interactions of the most active analogs 9d, 10a, 10b, and 10c with Elastase of Pseudomonas aeruginosa (PDB: 1U4G). The results indicated that these classes of compounds have potential antibacterial activity, especially the compound 10b may serve as a promising antibacterial lead compound that could be further optimized for the further development of antibacterial drugs. [ABSTRACT FROM AUTHOR]

Starting from phenylhydrazine and glucose, a versatile cinnoline scaffold was obtained on a multigram scale and further derivatized. A simple continuous-flow hydrogenation process permits the conversion of selected cinnolines into their 1,4-dihydrocinnoline counterparts. These products are generated in high yields and high purities with residence times of less than one minute and, along with their cinnoline precursors, are expected to serve as valuable heterocyclic building blocks for future medicinal chemistry programs. [ABSTRACT FROM AUTHOR]

A new type of fluorogenic and fluorochromic probe based on the reduction of weakly fluorescent 4-azido-6-(4-cyanophenyl)cinnoline to the corresponding fluorescent cinnoline-4-amine was developed. We found that the fluorescence of 6-(4-cyanophenyl)cinnoline-4-amine is strongly affected by the nature of the solvent. The fluorogenic effect for the amine was detected in polar solvents with the strongest fluorescence increase in water. The environment-sensitive fluorogenic properties of cinnoline-4-amine in water were explained as a combination of two types of fluorescence mechanisms: aggregation-induced emission (AIE) and excited state intermolecular proton transfer (ESPT). The suitability of an azide–amine pair as a fluorogenic probe was tested using a HepG2 hepatic cancer cell line with detection by fluorescent microscopy, flow cytometry, and HPLC analysis of cells lysates. The results obtained confirm the possibility of the transformation of the azide to amine in cells and the potential applicability of the discovered fluorogenic and fluorochromic probe for different analytical and biological applications in aqueous medium.

Novel poly(arylene ethynylene)s comprising a cinnoline core were prepared in high yields via a three-step methodology. A Richter-type cyclization of 2-ethynyl- and 2-(buta-1,3-diynyl)aryltriazenes was used for cinnoline ring formation, followed by a Sonogashira coupling for the introduction of trimethylsilylethynyl moieties and a sila-Sonogashira coupling as the polycondensation technique. The fluorescence of the cinnoline-containing polymers in THF was highly sensitive to quenching by Pd2+ ions.

A facile and moderately functional-group-tolerant synthetic method for the preparation of 7,8-diaza[5]helicenes has been developed. It comprises of an oxidative ring-closing process of 1,1’-binaphthalene-2,2’-diamine (BINAM) derivatives with a chlorine-containing oxidant (t-BuOCl) in the presence of a base (2,6-lutidine). In addition the basic physicochemical properties of newly synthesized compounds have been investigated.

An efficient approach towards the synthesis of 6-aryl-4-azidocinnolines was developed with the aim of exploring the photophysical properties of 6-aryl-4-azidocinnolines and their click reaction products with alkynes, 6-aryl-4-(1,2,3-1H-triazol-1-yl)cinnolines. The synthetic route is based on the Richter-type cyclization of 2-ethynyl-4-aryltriazenes with the formation of 4-bromo-6-arylcinnolines and nucleophilic substitution of a bromine atom with an azide functional group. The developed synthetic approach is tolerant to variations of functional groups on the aryl moiety. The resulting azidocinnolines were found to be reactive in both CuAAC with terminal alkynes and SPAAC with diazacyclononyne, yielding 4-triazolylcinnolines. It was found that 4-azido-6-arylcinnolines possess weak fluorescent properties, while conversion of the azido function into a triazole ring led to complete fluorescence quenching. The lack of fluorescence in triazoles could be explained by the non-planar structure of triazolylcinnolines and a possible photoinduced electron transfer (PET) mechanism. Among the series of 4-triazolylcinnoline derivatives a compound bearing hydroxyalkyl substituent at triazole ring was found to be cytotoxic to HeLa cells.

A novel method was developed for the construction of biologically active poly-substituted cinnolines from easily accessible hydrazones in good to excellent yields. A simple copper catalyst could efficiently promote C−N bond formation through selective C−H functionalization and dehydrogenative amination. Furthermore, the inert C−Heteroatom (O/F/N) bonds are susceptible to cleavage in high selectivity in the newly developed aerobic annulation, in preference to the alternative C−H bond, which is left intact. [ABSTRACT FROM AUTHOR]

A convenient, simple and efficient synthesis of polyfunctionally substituted cinnolines has been developed that involves the reaction of ethyl 5-cyano-4-methyl-1-aryl-6-oxo-1,6-dihydropyridazine-3-carboxylate with nitroolefins in dioxane/piperidine under controlled microwave irradiation. The obtained heterocycles are a privileged scaffold in a few natural compounds and in many drugs with a broad spectrum of biological activities. Graphical Abstract: [ABSTRACT FROM AUTHOR]

3-Oxo-3-phenyl-2-(p-tolylhydrazono)propanal (1a) undergoes condensation with ethyl cyanoacetate in acetic acid in the presence of ammonium acetate to yield either 2-hydroxy-6-phenyl-5-p-tolylazonicotinic acid ethyl ester (6a) or 2-amino-6-phenyl-5-p-tolyl-azonicotinic acid ethyl ester (8), depending on the reaction conditions. Similarly, other 3-oxo-3-aryl-2-arylhydrazonopropanals 1a,b condense with active methylene nitriles 2c,d to yield arylazonicotinates 6b,c. In contrast, 2-[(4-nitrophenyl)-hydrazono]-3-oxo-3-phenyl-propanal (1c) reacts with ethyl cyanoacetate to yield ethyl 6-(4-nitrophenyl)-2-oxo-2,6-dihydropyrido[3,2–c]cinnoline-3-carboxylate (11), via a novel 6π-electrocyclization pathway. Finally, 3-oxo-2-(phenylhydrazono)-3-p-tolylpropanal (1d) condenses with 2a–c to yield pyridazinones 13a–c.

Rhodium catalysis: A highly efficient and general method has been established to prepare cinnolines, cinnolinium salts, and polycyclic cinnolinium salts through the rhodium(III)‐catalyzed oxidative CH activation/cyclization of azo compounds with alkynes (see scheme). Key features of this methodology include the unprecedented capacity to create both cinnoline and cinnolinium frameworks. [ABSTRACT FROM AUTHOR]

Abstract: We report our successful effort to increase the PDE3 selectivity of PDE10A inhibitor pyridyl cinnoline 1 using a combination of computational modeling and structural–activity relationship investigations. An analysis of the PDE3 catalytic domain compared to the co-crystal structure of cinnoline analog 1 in PDE10A revealed two areas of structural differences in the active sites and suggested areas on the scaffold that could be modified to exploit those unique structural features. Once SAR established the cinnoline as the optimal scaffold, modifications on the methoxy groups of the cinnoline and the methyl group on the pyridine led to the discovery of compounds 33 and 36. Both compounds achieved significant improvement in selectivity against PDE3 while maintaining their PDE10A inhibitory activity and in vivo metabolic stability comparable to 1. [Copyright &y& Elsevier]

3-Oxo-3-phenyl-2-(p-tolylhydrazono)propanal (1a) undergoes condensation with ethyl cyanoacetate in acetic acid in the presence of ammonium acetate to yield either 2-hydroxy-6-phenyl-5-p-tolylazonicotinic acid ethyl ester (6a) or 2-amino-6-phenyl-5-ptolyl- azonicotinic acid ethyl ester (8), depending on the reaction conditions. Similarly, other 3-oxo-3-aryl-2-arylhydrazonopropanals 1a,b condense with active methylene nitriles 2c,d to yield arylazonicotinates 6b,c. In contrast, 2-[(4-nitrophenyl)-hydrazono]-3-oxo-3- phenyl-propanal (1c) reacts with ethyl cyanoacetate to yield ethyl 6-(4-nitrophenyl)-2-oxo- 2,6-dihydropyrido[3,2-c]cinnoline-3-carboxylate (11), via a novel 6π-electrocyclization pathway. Finally, 3-oxo-2-(phenylhydrazono)-3-p-tolylpropanal (1d) condenses with 2a-c to yield pyridazinones 13a-c. [ABSTRACT FROM AUTHOR]

Abstract: We report the discovery of 6,7-dimethoxy-4-(pyridin-3-yl)cinnolines as novel inhibitors of phosphodiesterase 10A (PDE10A). Systematic examination and analyses of structure–activity-relationships resulted in single digit nM potency against PDE10A. X-ray co-crystal structure revealed the mode of binding in the enzyme’s catalytic domain and the source of selectivity against other PDEs. High in vivo clearance in rats was addressed with the help of metabolite identification (ID) studies. These findings combined resulted in compound 39, a promising potent inhibitor of PDE10A with good in vivo metabolic stability in rats and efficacy in a rodent behavioral model. [Copyright &y& Elsevier]

A reaction of 4-( N-nitramino)-3-phenylfuroxane with the AcO/HSO system leads to the formation of [1,2,5]oxadiazolo[3,4- c]cinnoline-1,5-dioxide, the first representative of furoxanocinnolines. The reaction presumably proceeds through the transformation of the nitramine fragment NHNO to the oxodiazonium ion [N=N=O] with subsequent intramolecular attack by this cation on the phenyl ring. Furoxanocinnoline is also formed in the reaction of the 4-( N-nitramino)-3-phenylfuroxane O-methyl derivative with HSO. It is assumed that this reaction also proceeds with involvement of the intermediate cation [N=N=O] formed by the protonation of the N=N(O)OMe group and subsequent elimination of MeOH. 7-Nitro derivative is formed when furoxanocinnoline is nitrated with the concentrated HNO/HSO mixture. The compounds obtained were characterized by H, C, and N NMR spectroscopy. [ABSTRACT FROM AUTHOR]

A new method for the synthesis of benzotetrazine-1,3-dioxides was developed, which involves the reaction of 2-( tert-butyl- NNO-azoxy)- N-nitroanilines with the AcO/HSO system. This method was also used for the synthesis of [1,2,5]oxadiazolo[3,4- c]cinnoline-5-oxide from 3-nitramino-4-phenylfurazan. The suggested mechanism of these reactions involves the formation of the intermediate oxodiazonium ion, resulting from acetylation of the oxygen atom of the nitramine group, followed by protonation and ionic dissociation. Then the oxodiazonium ion enters the intramolecular reaction with the neighboring tert-butyl- NNO-azoxy or phenyl group to form the corresponding heterocyclic systems. [ABSTRACT FROM AUTHOR]

Methods for the synthesis of [1,2,5]oxadiazolo[3,4- c]cinnoline 5-oxides, which include the reaction of 3-nitramino-4-(R-phenyl)furazans or their O-methyl derivatives with electrophilic agents, have been developed. Unsubstituted [1,2,5]oxadiazolo[3,4- c]cinnoline 5-oxide was synthesized from 3-nitramino-4-phenylfurazan upon the action of phosphorus anhydride or oleum, as well as from O-methyl derivative of 3-nitramino-4-phenylfurazan upon the action of HSO, MeSOH, CFCOH and BF·EtO, while 6-, 7-, 8-, and 9-nitro-substituted [1,2,5]oxadiazolo[3,4- c]cinnoline 5-oxides - from the corresponding 3-nitramino-4-(nitrophenyl)furazans upon the action of the HSO-HNO nitrating mixture. A suggestion has been made that an oxodiazonium ion is formed in these reactions from nitramines or their O-methyl derivatives upon the action of electrophilic agents, which is further involved into the intra-molecular reaction of electrophilic aromatic substitution ( SAr) with the aryl group. The structure of [1,2,5]oxadiazolo[3,4- c]cinnoline 5- N-oxides was confirmed by H, C, and N NMR spectra. Theoretical studies by the B3LYP/6-311G(d,p) method of combined molecular system ( O-methylated 3-nitramino-4-phenylfurazan + [HSO]) resulted in calculation of thermodynamic parameters of the sequence of cascade elementary reactions leading to the formation of [1,2,5]oxadiazolo[3,4- c]cinnoline 5-oxide. [ABSTRACT FROM AUTHOR]

Abstract: The Fischer indole reaction between phenylhydrazines and tosyl-4-piperidone furnishes tetrahydropyrido[4,3-b]indoles. In a Witkop–Winterfeldt-oxidation using ozone such indole derivatives are converted into medium-sized dicarbonyl ring systems, which cyclize to pyrroloquinolones. A detailed study of the reaction intermediates and the characterization of a cinnoline betaine side product formed by an unprecedented ring closure mechanism are reported. [ABSTRACT FROM AUTHOR]

Abstract: The conventional Richter cyclization involves diazotization of 2-alkynylanilines with HX (aq) (X=Br or Cl) and NaNO2, followed by spontaneous ring closure to give a mixture of 4-halocinnoline and 4-cinnolinone products. The different products result from competing attack of X− and H2O, respectively, upon an intermediate 2-alkynylphenyl diazonium ion during the cyclization step. In order to improve the chemoselectivity of this reaction, we have utilized triazenes as masked diazonium ions. These can be unmasked using MeSO3H in anhydrous solvents and the resultant 2-alkynylphenyl diazonium ion cyclized chemoselectively by the incorporation of a specifically added nucleophile. This process has been extended to tethered nucleophiles, leading to a Richter induced co-cyclization process to give ring-fused cinnolines. [ABSTRACT FROM AUTHOR]

4-Acetyl-5,6-diphenylpyridazin-3(2H)-one was condensed with 6-chloro-3-formylchromone under different reaction conditions to yield the enone or pyranopyridazine. Both compounds were used in the synthesis of some new hetarylpyranopyridazines. Pyranodipyridazine was obtained via a sequence of reactions of 4-acetyl-5,6-diphenylpyridazin-3(2H)-one with diethyl carbonate, acetic anhydride, and 4-bromobenzenediazonium chloride. The reactions of pyridazinylbutane-1,3-dione with conc. H2SO4, POCl3, hydrazines, hydroxylamine hydrochloride, cyanoacetamide, thiourea, and thiosemicarbazone were also studied. [ABSTRACT FROM AUTHOR]

Abstract: Several 11-ethyl-2,3-dimethoxy-8,9-methylenedioxy-11H-isoquino[4,3-c]cinnolin-12-ones with varied functionality on the ethyl substituent have exhibited potent topoisomerase I (TOP1) targeting activity and antitumor activity. The influence of various polar substituents at the 2-position of the 11-ethyl substituent, including N-methylamine, N-isopropylamine, hydroxyl, and hydroxylamino groups, on TOP1-targeting activity and cytotoxicity was assessed. The N-methylamine and N-isopropylamine derivatives were also evaluated as antitumor agents in athymic nude mice with MDA-MB-435 human tumor xenografts. Both compounds were active as antitumor agents upon either parenteral or oral administration. [Copyright &y& Elsevier]

a-Isonitroso ketones, derivatives of tetrahydrobenzofurazan and furoxan, react with aldehydes (acetaldehyde and propionaldehyde) and morpholine to form derivatives of tetrahydropyrrolo[2,3-e]-2,1,3-benzoxadiazole 6-oxide. Treatment of the latter with hydrazine hydrate gave derivatives of 4,5-dihydro-1,2,5-oxadiazolo[3,4-f]cinnoline which are readily dehydrogenated with tetrachloro-benzoquinone to derivatives of 1,2,5-oxadiazolo[3,4-f]cinnoline. Reduction of tetrahydropyrrolo[2,3-e]-2,1,3-benzoxadiazole 6-oxides with sodium borohydride gave derivatives of N-hydroxyhexahydro-pyrrolo[2,3-e]-2,1,3-benzoxazole. [ABSTRACT FROM AUTHOR]

6-Acylmino-1-alkyl/aryl-4-oxo-1,4-dihydrocinnoline-3-carboxamides were synthesized in parallel from 6-nitro-4-oxo-1,4-dihydrocinnoline-3-carboxylic acid. The latter formed amides with amines bound to polystyrene-based resins via acid-labile linkers. N1 and N2-alkylation, followed by alkyl migration yielded only N1-alkylated products. Reduction of the 6-nitro group and acylation concluded the synthesis. [Copyright &y& Elsevier]

Syntheses of new sulfinylcinnolines, quinoxalines, quinazolines and phtalazines have been investigated starting from the appropriate halogenobenzodiazine derivatives. The latter were converted in one step to the corresponding sulfanyl benzodiazines which upon oxidation with m-CPBA led to the corresponding sulfoxide derivatives of benzodiazines in moderate to good yields. In parallel to this study, an improved method for the synthesis of 2-methylsulfinylquinoxaline starting from 2-sulfanylquinoxaline is also described and in the quinazoline series a synthetic route has been developed to prepare 2-tert-butyl-5-phenylsulfinylquinazoline with satisfactory yield as well as 2-tert-butyl-5-tert-butylsulfinyl-4(3H)-quinazolinone and 2-tert-butyl-8-tert-butylsulfinyl-4(3H)-quinazolinone. [Copyright &y& Elsevier]

The synthesis of a series of disubstituted (4-aminocinnolin-3-yl)-aryl-methanones from aryl-hydrazonomalononitrile in a one-step procedure is described. Cyclocondensation of (4-amino-6,8-dimethyl-cinnolin-3-yl)-phenyl-methanone with malononitrile, diethylmalonate, and dimethylacetamide-dimethylacetal gave the corresponding pyrido[3,2- c]cinnoline derivatives. Treatment of (4-amino-6,8-dimethyl-cinnolin-3-yl)-phenyl-methanone with triethyl-orthoacetate under reflux readily afforded the corresponding imidoester which underwent cyclization to a pyrido[3,2- c]cinnoline derivative. This starting compound could also be annelated to the corresponding 1,2-dihydro-4-aryl-2-oxo-pyrido[3,2- c]cinnoline derivatives via the (4-acetamidocinnolin-3-yl)-aryl-methanones. Chemical and spectroscopic evidences for the structures of the new compounds are presented. The effect of three of the compounds against sixty cancer types was tested. [ABSTRACT FROM AUTHOR]

A new type of fluorogenic and fluorochromic probe based on the reduction of weakly fluorescent 4-azido-6-(4-cyanophenyl)cinnoline to the corresponding fluorescent cinnoline-4-amine was developed. We found that the fluorescence of 6-(4-cyanophenyl)cinnoline-4-amine is strongly affected by the nature of the solvent. The fluorogenic effect for the amine was detected in polar solvents with the strongest fluorescence increase in water. The environment-sensitive fluorogenic properties of cinnoline-4-amine in water were explained as a combination of two types of fluorescence mechanisms: aggregation-induced emission (AIE) and excited state intermolecular proton transfer (ESPT). The suitability of an azide–amine pair as a fluorogenic probe was tested using a HepG2 hepatic cancer cell line with detection by fluorescent microscopy, flow cytometry, and HPLC analysis of cells lysates. The results obtained confirm the possibility of the transformation of the azide to amine in cells and the potential applicability of the discovered fluorogenic and fluorochromic probe for different analytical and biological applications in aqueous medium. [ABSTRACT FROM AUTHOR]

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Abstract: The cyclization of ortho-(arylethynyl)benzene diazonium salts (the Richter reaction) is studied. A reaction mechanism, which differs radically from that reported earlier is proposed and substantiated by experimental data and quantum-chemical calculations. [Copyright &y& Elsevier]

An efficient approach towards the synthesis of 6-aryl-4-azidocinnolines was developed with the aim of exploring the photophysical properties of 6-aryl-4-azidocinnolines and their click reaction products with alkynes, 6-aryl-4-(1,2,3-1H-triazol-1-yl)cinnolines. The synthetic route is based on the Richter-type cyclization of 2-ethynyl-4-aryltriazenes with the formation of 4-bromo-6-arylcinnolines and nucleophilic substitution of a bromine atom with an azide functional group. The developed synthetic approach is tolerant to variations of functional groups on the aryl moiety. The resulting azidocinnolines were found to be reactive in both CuAAC with terminal alkynes and SPAAC with diazacyclononyne, yielding 4-triazolylcinnolines. It was found that 4-azido-6-arylcinnolines possess weak fluorescent properties, while conversion of the azido function into a triazole ring led to complete fluorescence quenching. The lack of fluorescence in triazoles could be explained by the non-planar structure of triazolylcinnolines and a possible photoinduced electron transfer (PET) mechanism. Among the series of 4-triazolylcinnoline derivatives a compound bearing hydroxyalkyl substituent at triazole ring was found to be cytotoxic to HeLa cells. [ABSTRACT FROM AUTHOR]

Novel poly(arylene ethynylene)s comprising a cinnoline core were prepared in high yields via a three-step methodology. A Richter-type cyclization of 2-ethynyl- and 2-(buta-1,3-diynyl)aryltriazenes was used for cinnoline ring formation, followed by a Sonogashira coupling for the introduction of trimethylsilylethynyl moieties and a sila-Sonogashira coupling as the polycondensation technique. The fluorescence of the cinnoline-containing polymers in THF was highly sensitive to quenching by Pd(2+) ions.

A facile and moderately functional-group-tolerant synthetic method for the preparation of 7,8-diaza[5]helicenes has been developed. It comprises of an oxidative ring-closing process of 1,1'-binaphthalene-2,2'-diamine (BINAM) derivatives with a chlorine-containing oxidant (t-BuOCl) in the presence of a base (2,6-lutidine). In addition the basic physicochemical properties of newly synthesized compounds have been investigated.