Reaction of hydrazonoyl halides 49 1: Synthesis and antimicrobial activity of some new pyrimido[1,2-b][1,2,4,5]tetrazin-6-one,tetrazino[3,2-b]quinazolin-5-one,pyrimidino[1,2-b]1,2,4,5-tetrazin-5-one and triazolo[4,3-a]pyrimidine derivatives

Pyrimido[1,2-b][1,2,4,5]tetrazin-6-one, tetrazino[3,2-b]quinazolin-5-one, pyrimidino[1,2-b]1,2,4,5-tetrazin-5-one and triazolo[4,3-a]pyrimidine derivatives were synthesized from C-(4-methyl-2-phenyl)thiazol-5-oyl-N-phenyl-hydrazonoyl bromide and different pyrimidine-2-thiones. New compounds had their structures confirmed by elemental and spectral analysis and were screened antimicrobial activity.     

Structure-Based Design,Synthesis, and Biological Evaluation of Imidazo[4,5-b]Pyridin-2-one-Based p38 MAP Kinase Inhibitors: Part 2

We identified novel potent inhibitors of p38 mitogen-activated protein (MAP) kinase using a structure-based design strategy, beginning with lead compound, 3-(butan-2-yl)-6-(2,4-difluoroanilino)-1,3-dihydro-2H-imidazo[4,5-b]pyridin-2-one ( 1 ). To enhance the inhibitory activity of 1 against production of tumor necrosis factor-α (TNF-α) in human whole blood (hWB) cell assays, we designed and synthesized hybrid compounds in which the imidazo[4,5-b]pyridin-2-one core was successfully linked with the p-methylbenzamide fragment. Among the compounds evaluated, 3-(3-tert-butyl-2-oxo-2,3-dihydro-1H-imidazo[4,5-b]pyridin-6-yl)-4-methyl-N-(1-methyl-1H-pyrazol-3-yl)benzamide ( 25 ) exhibited potent p38 inhibition, superior suppression of TNF-α production in hWB cells, and also significant in vivo efficacy in a rat model of collagen-induced arthritis (CIA). In this paper, we report the discovery of potent, selective, and orally bioavailable imidazo[4,5-b]pyridin-2-one-based p38 MAP kinase inhibitors.     

Design,synthesis, and antimicrobial activity of novel spiroisoxazolo[2,3-b][1,2,4]thiadiazole-2,2′-thiazolidine- 4′-ones and spiroisoxazolo[2,3-b][1,2,4]oxadiazole-2, 2′-thiazolidine-4′-ones

A new synthetic strategy for the synthesis of novel 6-methyl-3′-aryl spiro[isoxazolo[2,3-b][1,2,4]thiadiazole-2,2′-thiazolidin]-4′-ones (9a–9e) and 6-methyl-3′-aryl spiro[isoxazolo[2,3-b][1,2,4]oxadiazole- 2,2′-thiazolidin]-4′-ones (12a–12e) analogs is described. These compounds showed significant antimicrobial activity against all the standard strains.     

Two-component,one-pot synthesis of pyrimido[1,2-b] [1,2,4,5]tetrazines

Derivatives containing the cyclohepta4′,5′thieno[2′,3′:4,5]pyrimido[1,2-b][1,2,4,5]-tetrazin-6-one system were prepared from the reaction of 3-amino-2-thioxo-1,2,3,5,6,7,8,9-octahydro-4H-cyclohepta[4,5]thieno[2,3-d]pyrimidin-4-one (5) or its 2-methylthio derivative 6 with hydrazonoyl chlorides 9. The mechanism of the studied reactions has been discussed and the biological activity of the isolated products has been evaluated.     

A novel synthesis of indeno[2',1': 5,6] pyrido[2,3- d ][1,2,4]triazolo[4,3- a ]pyrimidines

Reaction of 5-(4-chlorophenyl)-2-thioxo-2,3-dihydro-1H-indeno[2',1':5,6] pyrido[2,3-d]pyrimidine-4,6-dione with hydrazonoyl chlorides gave 1,2,4-triazolo[4,3-a]pyrimidine derivatives regioselectively in good yields. The structures of the newly synthesized compounds are established on the basis of chemical and spectroscopic evidence as well as their synthesis by alternative methods.     

Pyridine-2(1H)-thione in heterocyclic synthesis: synthesis and antimicrobial activity of some new thio-substituted ethyl nicotinate,thieno[2,3-b]pyridine and pyridothienopyrimidine derivatives

3-(4-Bromophenyl)-2-cyanoprop-2-enethioamide (1) reacted with ethyl 3-oxo-3-phenylpropanoate (2) to give ethyl 4-(4-bromophenyl)-5-cyano-2-phenyl-6-thioxo-1,6-dihydropyridine-3-carboxylate (3). Compound 3 was taken as a starting material for the synthesis of thio-substituted ethyl nicotinate derivatives 5a–d, which underwent cyclization to the corresponding thieno[2,3-b]pyridines 6a–d. Also 3 reacted with hydrazine hydrate to give the pyrazolo[3,4-b]pyridine derivative 7, which upon diazotization gave the diazonium derivative 8. Compound 6a condensed with dimethylformamide–dimethylacetal to afford thieno[2,3-b]pyridine derivative 9, which reacted with different amines 10a–e to afford the pyridothienopyrimidine derivatives 12a–e through the Dimroth rearrangement. Moreover, compound 6a reacted with different reagents to give pyridothienopyrimidine derivatives 14a and b, 17 and pyrazolothienopyridine derivative 18. In addition, acetylating compound 6c with chloroacetylchloride afforded the 3-[(2)-chloroacetylamino]thieno[2,3-b]pyridine derivative 20, which upon cyclization yielded the corresponding 2-chloromethylpyrido[3′,2′:4,5]thieno[3,2-d]pyrimidine derivative 21. Some of the newly synthesized compounds were screened in vitro for their antimicrobial activities.

     

2-Mercapto-4,6-disubstituted nicotinonitriles: versatile precursors for novel mono- and bis[thienopyridines]

A series of novel thieno[2,3-b]pyridines were prepared from the reaction of the appropriate bromoacetylbenzofurans or bromoacetylbenzothiazole with the corresponding pyridinethione derivatives in ethanolic sodium ethoxide at reflux. Moreover, new bis(thieno[2,3-b]pyridine) derivatives have also been synthesized by the reaction of the appropriate bis-bromoacetyl derivatives with the corresponding pyridinethiones in the presence of sodium ethoxide. Attempts to synthesize the target bis(thieno[2,3-b]pyridine) derivatives by bis-alkylation of the corresponding (thieno[2,3-b]pyridin-2-yl)(hydroxyphenyl)methanone with the appropriate dihaloalkanes using a mild base were unsuccessful.     

A short-cut to 2,7-dihydrothiopyrano[2,3-b]pyrrole

A simple original approach to earlier unknown parent 2,7-dihydrothiopyrano[2,3-b]pyrrole (5) from allyl isothiocyanate and propargyl bromide via one-pot synthesis and thermal rearrangement of 2-(prop-2-ynylsulfanyl)-1H-pyrrole (4) has been developed. The compound 5 in the present study was successfully examined as 2,7-dihydrothiopyrano[2,3-b]pyrrole scaffold in the synthesis of corresponding N- and C-pyrrolecarbodithioates.     

An efficient microwave-assisted synthesis of thieno[2,3- b ]quinolines under solvent-free conditions

A novel and efficient method for the synthesis of substituted thieno[2,3-b]quinolines has been developed. A simple one-pot reaction of 3-formyl-2-mercaptoquinolines 2a–l with 1-chloroacetone, 2-chloroacetamide, ethyl chloroacetate and 2-chloro-1-phenylethanone in presence of catalytic amount of potassium carbonate under microwave irradiation and solvent-free conditions gave thieno[2,3-b]quinolin-2-ylethanone derivatives 3a–e, thieno[2,3-b]quinoline-2-carboxamide derivatives 4a–e, ethyl thieno[2,3-b]quinoline-2-carboxylate 5a–e and phenyl(thieno[2,3-b]quinolin-2-yl)methanone derivatives 6a–e compounds respectively. The structures of all the newly synthesised compounds were elucidated on the basis of elemental analysis, IR, ¹H NMR and mass spectral data.     

SYNTHESIS OF DIHYDRODIOLS OF PHENANTHRO[3,4-b]THIOPHENE AND PHENANTHRO[4,3-b]THIOPHENE

A number of sulfur analogs of polynuclear aromatic hydrocarbons (thia-PAHs) have been identified in cigarette smoke condensate. Phenanthro[3,4-b]thiophene (P[3,4-b]T) and phenanthro[4,3-b]thiophene (P[4,3-b]T) are sulfur analogs of benzo[c]phenanthrene, which is known to be metabolized to one of the most tumorigenic fjord region diol epoxides tested thus far. Although fjord region diol epoxides of P[3,4-b]T and P[4,3-b]T are expected to be potent mutagens and tumorigens, these two thia-PAHs differ greatly in their mutagenic potencies. In contrast to P[3,4-b]T which is as mutagenic as benzo[a]pyrene, its isoster P[4,3-b]T is a nonmutagenic compound. In order to understand the basis underlying the difference in the mutagenic potency of P[3,4-b]T and P[4,3-b]T, we require these thia-PAHs and their dihydrodiol derivatives for investigating their metabolism and mutagenic/carcinogenic activity. In these studies, we have investigated the Suzuki cross-coupling reaction for an abbreviated synthesis of P[3,4-b]T, P[4,3-b]T, and their dihydrodiol derivatives from easily available reagents.     

Electrochemical behavior of a new <Emphasis Type="Italic">s</Emphasis>-triazine-based dendrimer

The electrochemical behavior of a new G-2-s-triazine-based dendrimer, 2,4,6-tris-{4-{4,6-bis-{4-{4,6-bis-[(1S,2S)-1,3-dihydroxy-1-(4-nitrophenyl)-prop-2-ylamino]-s-triazin-2-yl}-piperazin-1-yl}-s-triazin-2-yl}-piperazin-1-yl}-s-triazine, (I), was studied in dimethylsulfoxide solution by cyclic voltammetry, on platinum and graphite electrodes. The electrochemical properties of I were compared with that of one of its precursor, N-{4,6-bis{4-{4,6-bis[(1S,2S)-1,3-dihydroxy-1-(4-nitrophenyl)-prop-2-ylamino]-s-triazin-2-yl}-piperazin-1-yl}-triazin-2-yl}-piperazine), (II), together with that of the starting material, (1S,2S)-2-amino-1-(4-nitrophenyl)-propane-1,3-diol (“p-nitrophenylserinol”), (III).     

A Scaffold-Hopping Strategy toward the Identification of Inhibitors of Cyclin G Associated Kinase

We recently reported the discovery of isothiazolo[4,3-b]pyridine-based inhibitors of cyclin G associated kinase (GAK) displaying low nanomolar binding affinity for GAK and demonstrating broad-spectrum antiviral activity. To come up with novel core structures that act as GAK inhibitors, a scaffold-hopping approach was applied starting from two different isothiazolo[4,3-b]pyridines. In total, 13 novel 5,6- and 6,6-fused bicyclic heteroaromatic scaffolds were synthesized. Four of them displayed GAK affinity with K_d values in the low micromolar range that can serve as chemical starting points for the discovery of GAK inhibitors based on a different scaffold.     

Parallel Synthesis of Pyrrolo[3,2-f]quinolines (PQQ Skeleton) Library via a One-Pot Three-Component Reaction under Catalyst-Free Conditions

An efficient and straightforward synthetic protocol was developed for the diversity-oriented synthesis of 13-aryl-6,13-dihydrochromeno[4,3-b]pyrrolo[3,2-f]quinolin- 12(3H)-one and 10-aryl-3H-furo[3,4-b]pyrrolo[3,2-f]quinolin-9(7H)-one derivatives (PQQ skeleton) in high yields under catalyst-free conditions. This procedure includes a one-pot three-component reaction of aromatic aldehyde, 1H-indol-5-amine, and 1,3-dicarbonyl compounds to generate total of 25-Membered structurally interesting and pharmacologically significant PQQ skeletons for bio-active screening.     

Influence of an Alkoxy Group on Bis-Triazinyl-Pyridines for Selective Extraction of Americium(III)

The extraction of americium(III), curium(III), and lanthanides(III) from nitric acid by 2,6-bis-(5,6-dimethyl-[1,2,4]-triazin-3-yl)-pyridine and 2,6-bis-(5,6-dimethyl-[1,2,4]-triazin-3-yl)-4-methoxypyridine was studied. The physico-chemical properties of these ligands, such as the protonation and complexation constants, were also determined to describe the influence of different substituent groups. The selectivity of substituted-BTP was confirmed both in complexation and in solvent extraction experiments. The presence of an alkoxy-group in position 4 of the pyridine decreases the BTP selectivity. Influence of a long alkyl chain on protonation and complexation constants was also studied with 2,6-bis-(5,6-dimethyl-[1,2,4]-triazin-3-yl)-4-dodecyloxypyridine.     

A convenient [hydroxy(tosyloxy)iodo]benzene-mediated one-pot synthesis of 2-arylimidazo[2,1-b]benzothiazoles

Several 2-arylimidazo[2,1-b]benzothiazoles (4) have been conveniently synthesized in one-pot reactions via α-tosyloxylation of enolizable ketones (1) using [hydroxy(tosyloxy)iodo]benzene 2 in acetonitrile, followed by treatment with 2-amino-6-(substituted)benzothiazoles (3). The present protocol offers several advantages towards general access of 2-arylimidazo[2,1-b]benzothiazoles, including an intriguing alternative to the literature protocols, a readily available nontoxic reagent, operational simplicity and an environmentally benign procedure.     

Enantiopreferential DNA-binding of a novel dinuclear complex [(bpy)2Ru(bdptb)Ru(bpy)2]4+

A novel dinuclear ruthenium(II) complex [(bpy)₂Ru(bdptb)Ru(bpy)₂]⁴⁺ (bpy=2,2^′-bipyridyl; bdptb=2,2^′-bis(5,6-diphenyl-1,2,4-triazin-3-yl)-4,4^′-bipyridine) has been synthesized and characterized. The DNA-binding behaviors of this complex have been studied by viscosity, absorption and circular dichroism (CD) spectra. It has firstly been found that the dinuclear ruthenium(II) complex display the enantiopreferential DNA-binding after equilibrium dialysis.     

Mapping the Melatonin Receptor. 8. Selective MT2 Agonists Derived from 5,6-Dihydroindolo[2,1-a]isoquinolines and Related Systems

A series of substituted indolo[2,1-a]isoquinolines and indolo[1,2-a]benzoxazines have been prepared, as melatonin analogues, to investigate the nature of the binding site of the melatonin receptor. Agonist and antagonist potency of all the analogues was measured using the [35S]GTPγS binding assay protocol. The binding affinity of the analogues were measured by competition binding studies against the human MT1 (hMT1) and MT2 (hMT2) receptors stably transfected in Chinese Hamster Ovarian (CHO) cells, using 2-[¹²⁵I]-iodomelatonin, as a ligand. N-Acetyl 2-(10-methoxy-5,6-dihydroindolo[2,1-a]isoquinolin-12-yl)propyl-1-amine (12 a) binds strongly to both the hMT1 and hMT2 receptors, and shows a preference for the hMT2, as does its propanamido counterpart 12 b . The introduction of two methyl groups into their side chain, analogues 15 a and 1 5 b , leads to antagonism, in the case of the former, and drastically diminishes its hMT1 binding; an analogous profile is seen for 15 b , which, however, is a partial agonist. Introduction of chlorine or methoxy groups into ring 4 gives compounds, that are weakly binding, with a preference for MT2. Substitution of oxygen for carbon at position 5 gives the indolo[1,2-c]benzoxazines 33 , 36 a and b , that bind strongly to the human receptors, 33 , 36 b being potent agonists at the melatonin receptors, but do not discriminate between hMT1 and hMT2.     

Syntheses and optical,electrochemical, and photovoltaic properties of polymers with 6-(2-thienyl)-4H-thieno[2,3-b]indole with a variety of electron-deficient units

Conjugated polymers were synthesized and used for polymer solar cells with new electron-rich units, 6-(2-thienyl)-4H-thieno[2,3-b]indole (2-TTI). 2-TTI was coupled with electron-pulling units, including benzothiadiazole and benzimidazole derivatives, to provide push–pull types of conjugated polymers (poly(8-(heptadecan-9-yl)-6-(thiophen-2-yl)-8H-thieno[2,3-b]indole)-alt-(2-methyl-5,6-bis(octyloxy)-4,7-di(thiophen-2-yl)-2-(trifluoromethyl)-2H-benzimidazole) (PTTIDOCF3), poly(8-(heptadecan-9-yl)-6-(thiophen-2-yl)-8H-thieno[2,3-b]indole)-alt-(5,6-bis(octyloxy)-4,7-di(thiophen-2-yl)-2,1,3-benzothiadiazole) (PTTIDOBT), poly(8-(heptadecan-9-yl)-6-(thiophen-2-yl)-8H-thieno[2,3-b]indole)-alt-(2,2-dimethyl-4,7-di(thiophen-2-yl)-2H-benzimidazole) (PTTIMBI), and poly(8-(heptadecan-9-yl)-6-(thiophen-2-yl)-8H-thieno[2,3-b]indole)-alt-(2,2-dimethyl-5,6-bis(octyloxy)-4,7-di(thiophen-2-yl)-2H-benzimidazole) (PTTIDOMBI)). The synthesized conjugated polymers provided deep highest occupied molecular orbital energy levels for higher open-circuit voltages (V_OC). The device composed of PTTIDOMBI and [6,6]-Phenyl C₇₁ butyric acid methyl ester PC₇₁BM (1:2) with chloronaphthalene additive showed a V_OC of 0.72 V, a short-circuit current (J_SC) of 9.16 mA/cm², and a fill factor of 0.43; this gave a power conversion efficiency (PCE) of 2.84%. The PTTIDOMBI provided better morphology for enhanced charge transport, and this led to the higher J_SC and PCE of the organic solar cells. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47624.     

Thia- and selenaheterocycles by a four-component reaction using elemental sulfur and selenium

The course of the four-component reactions of (2-benzimidazolyl) acetonitrile, carbondisulfide, isothiocyanate, and sulfur and selenium, respectively, is quite different. Whereas in the case of sulfur a tetracyclic [1,3]thiazolo[4′,5′:4,5]pyrimido[1,6-a]benzimidazol-2(3H)-thione is formed, a zwitterionic 7-(benzimidazolium-2-yl)-[1,2]thiaselenolo[2,3-b][1,2,4]thiaselenazole-6-thiolate (an azaselenadithiapentalene) is the product in the case of selenium. The structures of the products have been established by X-ray crystallography, and reaction mechanisms for their formation are proposed.     

Heterocyclic Synthesis with Nitriles: Synthesis of some novel pyrrolo [2,1-b]thiadiazoline,pyrrolo[2,1-b]thiadiazolo[3,2-a]pyrimidine and pyridine derivatives

α-(Bromothiocyanatomethyl)benzylidenemalononitrile ( 1 ) reacts with the hydrazides 2a – c , cyanoacethoydrazide ( 2d ,) cyanoacetamide ( 3a ) and cyanoacetanilides 3b – d to afford pyrrolo[2,1-b]thiadiazolines 5a – c , pyrrolo[2,1-b]thia-diazolo[3,2-a]pyrimidine ( 8 ) and the pyridone derivatives 11a – d . Structures and conceivable mechanisms are discussed.